Test Bank For Microbiology With Diseases By Taxonomy, 3rd Edition

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) In microbiology, the term growth usually refers to which of the following? 1) _______ A) an increase in the number of microbial cells B) an increase in the number and size of microbial cells C) an increase in a microbe’s size D) an increase in the amount of ATP produced E) an increase in the number and size of microbial cells and the amount of ATP produced 2) A cell that uses an organic carbon source and obtains energy from light would be called a A) photoautotroph. B) lithoautotroph. C) chemoautotroph. D) photoheterotroph. E) chemoheterotroph. 2) _______ 3) A(n) ________ organism is one that requires oxygen for growth. A) anaerobic B) obligate aerobic C) facultative anaerobic D) aerotolerant E) both aerotolerant and anaerobic 3) _______ 4) An aquatic microbe that can grow only at the surface of the water is probably which of the following? A) an anaerobe B) a heterotroph C) a chemotroph D) a lithotroph E) a phototroph 4) _______ 5) Which of the following forms of oxygen is detoxified by the enzyme catalase? A) singlet oxygen B) molecular oxygen C) peroxide anion D) superoxide radical E) hydroxyl radical 5) _______ 6) All of the following are used to protect organisms from the toxic by-products of oxygen EXCEPT A) carotenoids. B) protease. C) superoxide dismutase. D) peroxidase. E) catalase. 6) _______ 7) A microbe that grows only at the bottom of a tube of thioglycollate medium is probably a(n) A) facultative anaerobe. B) microaerophile. C) aerotolerant anaerobe. D) obligate anaerobe. E) obligate aerobe. 7) _______ 8) Nitrogen is a growth limiting nutrient for many organisms because A) only a small number of bacteria are able to extract it from the atmosphere. B) it is required for lipid synthesis. C) only a few microbes can extract it from the atmosphere, but all organisms require it for amino acid and nucleotide synthesis. D) it is required for synthesis of nucleotides. E) it is necessary for the biosynthesis of amino acids. 8) _______ 9) All of the following are examples of growth factors used by microbes EXCEPT A) heme. B) NADH. C) amino acids. D) selenium. E) vitamins. 9) _______ 10) At temperatures higher than the maximum growth temperature for an organism, A) hydrogen bonds are broken, proteins are denatured, and membranes become too fluid. B) membranes become too fluid for proper function. C) hydrogen bonds within molecules are broken. D) hydrogen bonds are broken, and proteins are permanently denatured. E) proteins are permanently denatured. 10) ______ 11) Human pathogens are classified as A) psychrophiles. B) hyperthermophiles. C) thermoduric. D) mesophiles. E) thermophiles. 11) ______ 12) The term barophile refers to which of the following growth requirements? A) pH B) nitrogen source C) osmotic pressure D) temperature E) hydrostatic pressure 12) ______ 13) Which of the following organisms would be most likely to contaminate a jar of pickles? A) an acidophile B) a thermophile C) an obligate anaerobe D) a mesophile E) a neutrophile 13) ______ 14) Organisms that can grow with or without oxygen present are A) aerotolerant anaerobes. B) facultative anaerobes. C) obligate aerobes. D) obligate anaerobes. E) either facultative anaerobes or aerotolerant anaerobes. 14) ______ 15) A fastidious organism might be grown on which of the following types of media? A) enriched media 15) ______ B) transport media C) differential media D) selective media E) reducing media 16) Obligate anaerobes may be cultured in the laboratory A) on blood agar plates in a candle jar. B) in a reducing medium. C) on blood agar plates. D) in a candle jar. E) in standard Petri plates. 16) ______ 17) Joan wants to discover a microbe capable of degrading an environmental contaminant. Which of the following refers to the process she should use? A) quorum sensing B) binary fission C) enrichment culture D) nitrogen fixation E) lyophilization 17) ______ 18) A microbiologist inoculates a growth medium with 100 bacterial cells/ml. If the generation time of the species is 1 hour, how long will it be before the culture contains more than 10,000 cells/ml? A) 3 hours B) 2 hours C) 10 hours D) 7 hours E) 24 hours 18) ______ 19) An epidemiologist is investigating a new disease and observes what appear to be bacteria inside tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the lab. What culture conditions are most likely to be successful? A) inoculation of EMB plates B) incubation in a candle jar C) culturing on blood agar plates D) inoculation of cell cultures E) inoculation of a minimal medium broth 19) ______ 20) Which of the following measurement techniques would be useful to quantify a species of bacteria that is difficult to culture? A) membrane filtration B) microscopic counts C) metabolic activity D) viable plate counts E) MPN 20) ______ 21) MacConkey agar plates represent ________ medium. A) a differential B) a selective C) a minimal D) both a differential and a selective E) both a minimal and a selective 21) ______ 22) A Petroff-Hauser counting chamber is A) a glass slide containing an etched grid for counting microbes directly using a microscope. B) a device that counts cells as they interrupt an electrical current. C) a device used to count numbers of bacterial colonies on a Petri plate. 22) ______ D) an apparatus that traps bacterial cells on a membrane filter where they can be counted. E) a device that measures the amount of light that passes through a culture. 23) Another term for the logarithmic growth of bacterial cells is A) arithmetic growth. B) generation time. C) absorbance. D) exponential growth. E) binary fission. 23) ______ 24) A device that removes wastes and adds fresh medium to bacterial cultures in order to prolong the log phase of a culture is called a(n) A) cytometer. B) pellicle. C) spectrophotometer. D) chemostat. E) Coulter counter. 24) ______ 25) A specimen of urine is determined to contain 30 bacterial cells per microliter. How many cells would be present in a milliliter? A) 3 B) 30,000 C) 3,000 D) 30 million E) 300 25) ______ 26) Which of the following is NOT a direct method for measuring the number of microbes in a sample? A) membrane filtration B) Coulter counter C) turbidity D) viable plate counts E) MPN 26) ______ 27) During which growth phase are bacteria more susceptible to antimicrobial drugs? A) stationary phase B) log phase C) lag phase D) death phase E) the susceptibility is the same for all phases 27) ______ 28) The use of salt and sugar in preserving various types of foods is an application of which of the following concepts? A) quorum sensing B) nitrogen fixation C) pH D) osmotic pressure E) hydrostatic pressure 28) ______ 29) A clinical sample labeled as “sputum” was collected from A) the skin. B) the blood. C) the lungs. D) a piece of tissue. E) the central nervous system. 29) ______ 30) The method of obtaining isolated cultures that utilizes surface area to dilute specimens is called A) transport media. B) enrichment culturing. C) the streak-plate technique. D) serial dilution. E) the pour-plate technique. 30) ______ 31) ________ are complex communities of various types of microbes that adhere to surfaces. A) Isolates B) Media C) Colonies D) Biofilms E) Aggregates 31) ______ 32) A colony-forming unit is the number of cells A) that can be placed on a Petri plate. B) that produces one colony. C) in a particular specimen. D) in a colony. E) that is in exponential phase in a culture. 32) ______ 33) All of the following ingredients might be found in complex media EXCEPT A) blood. B) soy extract. C) hydrogen peroxide. D) yeast extract. E) milk proteins. 33) ______ 34) Sodium thioglycollate is associated with which of the following types of media? A) transport media B) reducing media C) complex media D) differential media E) selective media 34) ______ 35) Which of the following quantification techniques can distinguish living cells from dead cells in a culture? A) a Coulter counter B) metabolic activity C) dry weight D) microscopic counts E) turbidity 35) ______ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Match the statements with the appropriate phase of the bacterial growth curve: A) Lag phase B) Log phase C) Death phase D) Stationary phase 36) New cells are being produced at the same rate as other cells are dying 36) _____________ 37) Cells are dying faster than new cells are being produced 37) _____________ 38) Cells are metabolically active but not dividing 38) _____________ 39) The phase normally maintained by means of a chemostat 39) _____________ 40) Cells are rapidly growing and dividing 40) _____________ Match each term with the appropriate description: A) Hydrostatic pressure B) Salt concentration C) pH D) Carbon dioxide levels E) Oxygen levels 41) Halophile 41) _____________ 42) Capnophile 42) _____________ 43) Barophile 43) _____________ 44) Microaerophile 44) _____________ 45) Acidophile 45) _____________ TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false. 46) Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the damaging effects of oxygen. 46) ______ 47) Nitrogen fixation is a process that occurs in all bacteria. 47) ______ 48) Thermoduric mesophiles are often responsible for spoilage of improperly canned foods. 48) ______ 49) An obligate halophile will burst if placed in freshwater. 49) ______ 50) The only effective way to store bacterial cultures for short periods of time is to arrest their metabolism by freezing. 50) ______ 51) Quorum sensing is a process by which bacteria respond to the density of other bacteria in their environment. 51) ______ 52) An obligate anaerobe can be cultured in a candle jar. 52) ______ 53) Agar is a useful compound in the microbiology lab because it is an excellent nutrient for bacteria. 53) ______ 54) A selective medium can be formulated either by including inhibitory chemical substances or by leaving out a single crucial nutrient. 54) ______ 55) In spectrophotometry, 40% light transmission is the same thing as 60% absorbance of light. 55) ______ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Correct answers may contain more than one word. 56) The conversion of nitrogen gas to ammonia is called ________. 56) _____________ 57) ________ are organisms that require organic sources of carbon and energy. 57) _____________ 58) The ________ radical is formed during the incomplete reduction of O 2 during electron 58) _____________ transport in aerobes. 59) The ________ growth temperature is the temperature at which an organism exhibits the highest growth rate. 59) _____________ 60) Bacteria that thrive at human body temperatures are classified as ________. 60) _____________ 61) ________ can survive in water up to pH 11.5. 61) _____________ 62) Cells that are exposed to hypertonic environments will exhibit ________. 62) _____________ 63) A(n) ________ is a sample of microorganisms introduced into a growth medium. 63) _____________ 64) A(n) ________ is composed of cells that arise from a single colony. 64) _____________ 65) ________ is a gelling agent derived from algae that is useful for creating solid growth media. 65) _____________ 66) A sample placed into fresh medium is typically initially in the ________ phase of microbial growth. 66) _____________ 67) A(n) ________ plots the number of organisms in a growing population over time. 67) _____________ 68) ________ is a method of counting cells that have been stained or tagged with fluorescent dyes. 68) _____________ 69) A film of cells at the surface of a broth is called a(n) ________. 69) _____________ 70) A(n) ________ can measure changes in the turbidity of a bacterial culture. 70) _____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 71) Explain how aerobic organisms tolerate the presence of oxygen in their metabolic pathways despite its toxic properties. 72) Explain how temperature and pH levels can influence microbial infections in the human body. 73) Compare and contrast the streak-plate method of isolation with the pour-plate method of isolation. 74) Genetic methods of detecting microorganisms reveal that the number of bacterial species in nature exceeds previous estimates by several orders of magnitude. In the human mouth, for example, it is estimated that 500—700 microbial species are normally present. Explain why previous estimates were low. 75) Explain the similarities and differences between direct and indirect methods of measuring microbial growth, and give examples of each. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 76) All of the following are associated with nucleic acid structure EXCEPT A) phosphate. B) ionic bonds. C) ribose. D) hydrogen bonds. E) uracil. 76) ______ 77) Which of the following is found at the 5 end of a DNA strand? A) a phosphate group B) a hydroxyl group C) a hydrogen bond D) histones E) a methyl group 77) ______ 78) The bacterial chromosome is A) found in a nucleus. B) found in a nucleoid. C) usually circular. D) both circular and found in a nucleoid. E) both circular and found in a nucleus. 78) ______ 79) Which of the following types of plasmids allows a bacterial cell to kill its competitors? A) bacteriocin factors B) virulence factors C) fertility factors D) cryptic plasmids E) resistance factors 79) ______ 80) Which of the following is NOT involved the packaging of eukaryotic chromosomes? A) heterochromatin B) nucleosomes C) Okazaki fragments D) histones E) euchromatin 80) ______ 81) Which of the following statements is true of bacterial plasmids? A) They are small circular DNA molecules. B) They can replicate autonomously. C) They are found in the nucleoid. D) They carry genes for essential metabolic functions. E) They are small circular DNA molecules that can replicate autonomously. 81) ______ 82) DNA helicases A) synthesize short DNA molecules important for the function of DNA polymerase. B) assist in recognition of promoters during transcription. C) break hydrogen bonds between complementary nucleotides. D) proofread DNA molecules. E) seal gaps between DNA fragments. 82) ______ 83) Which of the following statements concerning transcription in bacteria is FALSE? A) It occurs in the nucleoid region. B) The same RNA polymerase transcribes primer RNA, mRNA, tRNA, and rRNA. 83) ______ C) Sigma factors are parts of RNA polymerase that recognize promoter regions. D) There are a variety of sigma factors that affect transcription. E) Termination is either self-induced or due to the presence of Rho protein. 84) Which of the following is involved in translation? A) both mRNA and tRNA B) mRNA, rRNA and tRNA are all involved. C) tRNA D) rRNA E) mRNA 84) ______ 85) Which of the following is a characteristic shared by DNA and RNA polymerases? A) speed B) dependence on helicase C) type of nucleotides used D) efficiency of proofreading E) direction of polymerization 85) ______ 86) Which of the following is the strongest base pair? A) both adenine-uracil and adenine-thymine B) adenine-uracil C) guanine-cytosine D) guanine-thymine E) adenine-thymine 86) ______ 87) A codon is a particular combination of three nucleotides. Therefore, there are ________ possible combinations of the nucleotides A, C, G, and T. A) 32 B) 16 C) 4 D) 12 E) 64 87) ______ 88) The AUG codon functions in coding for the amino acid methionine and as a A) start signal. B) recognition site for RNA polymerase. C) “wobble” codon. D) termination signal. E) marker for introns. 88) ______ 89) Which of the following must be removed from a eukaryotic mRNA molecule before it can be translated? A) exon B) codon C) intron D) anticodon E) promoter 89) ______ 90) A charged tRNA first enters the ribosomal ________ site and then moves into the ________ site. A) A, P B) P, E C) P, A D) A, E E) E, A 90) ______ 91) Which of the following statements regarding eukaryotic transcription is FALSE? A) Multiple transcription factors are required. B) Transcription occurs in the nucleus, mitochondria, and chloroplasts (if present). C) A guanine is added to the 3 end, and a poly-A tail is added to the 5 end of the mRNA transcript. D) There are four different RNA polymerases. E) Multiple elongation factors are required. 91) ______ 92) Semiconservative DNA replication means that 92) ______ A) the sequence of a DNA molecule is preserved as it is being replicated. B) nucleotides are constantly being recycled as cells make DNA. C) each daughter DNA molecule is composed of one original strand and one new strand. D) each strand of a double-stranded DNA molecule is replicated differently. E) the cell can proofread its newly synthesized DNA only part of the time. 93) Which of the following is NOT a characteristic of Okazaki fragments? A) They make up the lagging strand of replicated DNA. B) They begin with an RNA primer. C) They are joined together by DNA ligase. D) They are checked for accuracy by DNA polymerase III. E) They are longer in eukaryotic cells. 93) ______ 94) The proofreading function of DNA polymerase III results in an error rate of ________ during DNA replication. A) 1 error in 1,000 bases B) 1 error in 100,000 bases C) 1 error in 1 million bases D) 1 error in 10 million bases E) 1 error in 10 billion bases 94) ______ 95) Which of the following processes is involved in the “central dogma” of genetics? A) transcription and translation B) transcription C) DNA replication D) DNA replication and translation E) translation 95) ______ 96) Inducible operons A) usually require a repressor to be transcribed. B) are active in the presence of a repressor. C) are normally active. D) are generally anabolic pathways. E) usually require an activator to be transcribed. 96) ______ 97) Which of the following are considered to be frameshift mutations? A) insertions B) deletions C) inversions D) both inversion and insertions E) both deletions and insertions 97) ______ 98) If the codon AAA is changed to AAG, it still codes for the amino acid lysine; this is an example of a A) silent mutation. B) frameshift mutation. C) missense mutation. D) nonsense mutation. E) gross mutation. 98) ______ 99) Which of the following causes mutations by creating thymine dimers? A) nucleotide analogs 99) ______ B) ultraviolet light C) nitrous acid D) benzopyrene E) gamma rays 100) DNA damage caused by ethidium bromide results in ________ mutations. A) insertion B) deletion C) substitution D) both inversion and insertion E) both insertion and deletion 100) _____ 101) Which of the following is a DNA repair enzyme activated by visible light? A) DNA ligase B) bacteriocin C) transposase D) DNA photolyase E) primase 101) _____ 102) The Ames test proves that a chemical is A) carcinogenic in Salmonella. B) mutagenic in humans. C) carcinogenic. D) carcinogenic in humans. E) mutagenic in Salmonella. 102) _____ 103) The horizontal transfer process known as transduction A) requires a cell to be “competent.” B) requires a pilus. C) requires a plasmid. D) involves a virus. E) involves a mutagen. 103) _____ 104) Frederick Griffith discovered A) the lac operon. B) transposons. C) conjugation. D) DNA. E) transformation. 104) _____ 105) In conjugation, F+ cells A) serve as recipient cells. B) do not have conjugation pili. C) can transfer DNA only to other F+ cells. D) contain an F plasmid. E) contain “jumping genes.” 105) _____ 106) Another term for the palindromic sequence found at the ends of transposons is a(n) A) inverted repeat. B) bacteriophage. C) transposase. D) complex transposon. 106) _____ E) insertion sequence. 107) Which of the following is characteristic of prokaryotic genomes but NOT eukaryotic genomes? A) circular chromosomes B) typically consist of a few to several chromosomes C) enclosed in a nuclear membrane D) linear chromosomes E) histones 107) _____ 108) Genes are active in a region of the eukaryotic chromosome called A) the plasmid. B) the histone. C) the nucleoid. D) heterochromatin. E) euchromatin. 108) _____ 109) The energy required for DNA replication comes from A) DNA ligase. B) RNA primer. C) the leading strand. D) DNA polymerase. E) triphosphate deoxyribonucleotides. 109) _____ 110) Which of the following is NOT involved in the regulation of the lac operon? A) a repressor protein B) an inducer C) an iRNA D) cyclic AMP E) glucose 110) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Match the term with the appropriate genetic process: A) Transcription B) DNA replication C) Translation 111) Promoter 111) ____________ 112) Codon 112) ____________ 113) Origin 113) ____________ 114) DNA ligase 114) ____________ 115) RNA polymerase 115) ____________ 116) tRNA 116) ____________ 117) fMet 117) ____________ 118) Sigma factor 118) ____________ 119) Semiconservative 119) ____________ 120) P site 120) ____________ TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false. 121) Prokaryotic cells are diploid. 121) _____ 122) Prokaryotes have one type of DNA polymerase, which is different from that of eukaryotes. 122) _____ 123) The most common type of mutation is a point mutation. 123) _____ 124) Most bacteria have a natural ability to take up DNA from their environment. 124) _____ 125) The structure of DNA explains both its ability to encode genetic information and the way in which it is copied during cell reproduction. 125) _____ 126) DNA, which is negatively charged, wraps around positively charged histones as part of the packaging of eukaryotic chromosomes. 126) _____ 127) Bidirectional replication means that each strand of a DNA molecule is replicated in the opposite direction from the other. 127) _____ 128) The phenotype of an organism reflects only part of its genotype. 128) _____ 129) In generalized transduction, viruses carry random DNA sequences from one cell to another. 129) _____ 130) DNA polymerase III participates in the dark repair mechanism of DNA mutation repair. 130) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Correct answers may contain more than one word. 131) A(n) ________ is a specific sequence of nucleotides that codes for a protein or an RNA molecule. 131) ____________ 132) Loosely packed regions of a eukaryotic chromosome are called ________. 132) ____________ 133) Transfer of DNA between cells by viruses is called ________. 133) ____________ 134) A(n) ________ is a mutant organism that has different nutritional requirements from the original wild-type organism. 134) ____________ 135) The enzyme that removes supercoils generated during DNA replication is ________. 135) ____________ 136) 5-bromouracil mimics the chemical structure of thymine, making it a(n) ________. 136) ____________ 137) A mutation that changes the reading frame of a gene is called a ________ mutation. 137) ____________ 138) The ________ of a transfer RNA molecule is complementary to a codon in a messenger RNA molecule. 138) ____________ 139) Transfer RNA molecules carrying amino acids initially bind to the ribosome at the ________. 139) ____________ 140) dATP and dCTP are examples of ________, the building blocks of DNA molecules. 140) ____________ 141) A(n) ________ is a set of prokaryotic genes that are regulated and transcribed as a unit. 141) ____________ 142) The ________ is the DNA strand that is synthesized continuously during DNA replication. 142) ____________ 143) The ________ is the set of genes in the genome of an organism. 143) ____________ 144) RNA polymerase initiates transcription by recognizing specific nucleotide sequences called ________. 144) ____________ 145) ________ RNA molecules contain both introns and exons. 145) ____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 146) Describe the basic similarities and differences between DNA replication and transcription. 147) Describe the various types of nucleic acids that are typically found in cells. 148) Discuss some of the consequences of the significant differences in transcription between prokaryotes and eukaryotes. 149) Compare and contrast the lactose operon with the tryptophan operon. 150) A point mutation can be completely harmless, or it can result in the death of a cell or organism. Explain why these types of mutations can have such varying effects. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 151) Which of the following processes did NOT contribute to the development of genetic 151) _____ engineering? A) chemiosmosis B) transformation C) conjugation D) transcription E) transduction 152) In the 20th century, scientists harnessed the natural metabolic reactions of bacteria to make ________ for the first time in an industrial setting. A) bread B) alcohol C) cheese D) soy sauce E) acetone 152) _____ 153) Which of the following items is NOT a part of the name of a restriction enzyme? A) the Gram reaction of the source bacterium B) the strain of the source bacterium C) the genus of the source bacterium D) the specific epithet of the source bacterium E) Roman numerals to indicate its order of discovery 153) _____ 154) The natural role of restriction enzymes in bacteria is A) to make conjugation more efficient. B) to allow transposons to move to another place in the chromosome. C) to protect the cell from invading phages. 154) _____ D) to provide the cell with new phenotypes, such as antibiotic resistance. E) to allow cells to accept foreign DNA. 155) A library of cloned sequences representing the expressed genes of an organism is known as a(n) A) microarray. B) gene library. C) cDNA library. D) DNA fingerprint. E) FISH library. 155) _____ 156) Which of the following restriction enzyme sites would produce blunt-ended fragments (the arrow represents the cutting site of the enzyme)? A) C↓CGG B) CCC↓GGG C) G↓AATTC D) G↓GATCC E) A↓AGCTT 156) _____ 157) Put the following steps in the correct order needed to produce a recombinant vector containing a human gene insert. I. Introduce the recombinant plasmid into a bacterial cell. II. Isolate the human gene and the vector DNA using restriction enzymes. III. Ligate the DNA fragments to produce a recombinant plasmid. IV. Grow bacterial cells on a medium containing a selective agent (such as an antibiotic). A) I, III, IV, II B) II, I, III, IV C) II, III, I, IV D) III, I, IV, II E) III, I, II, IV 157) _____ 158) Which of the following statements regarding vectors is FALSE? A) Cloning vectors frequently contain sequences necessary for expression of inserted sequences. B) Vectors are generally over 100,000 base pairs in size. C) A useful vector contains multiple restriction sites for insertion of DNA. D) Cloning vectors include a “marker” to facilitate identification of cells containing them. E) Vectors are usually autonomously replicating DNA molecules. 158) _____ 159) Synthetic nucleic acids are useful A) as DNA probes, primers, and antisense RNAs. B) as DNA probes. C) as antisense RNAs. D) as primers for PCR. E) as DNA probes and antisense RNAs. 159) _____ 160) Which of the following would be an appropriate temperature for the first step of PCR? A) 72°C B) 65°C C) 94°C D) 37°C E) 55°C 160) _____ 161) Which of the following is essential in PCR? A) DNA polymerase B) DNA primers C) antisense RNAs D) reverse transcriptase E) both DNA primers and DNA polymerase 161) _____ 162) If a researcher used Escherichia coli DNA polymerase instead of Thermus aquaticus DNA poly meras e in the 162) PCR procedur e, what would be the result? A) PCR would not occur at all. B) PCR would occur twice as fast as normal. C) PCR would stop after one cycle. D) PCR would occur more slowly than normal. E) Many mistakes would occur. ____ _ 163) Which of the following would be an appropriate sequence of temperatures for PCR? A) 94°C, 65°C, 72°C B) 94°C, 55°C, 37°C C) 72°C, 65°C, 94°C D) 65°C, 72°C, 94°C E) 94°C, 37°C, 55°C 163) _____ 164) If you started with a single DNA molecule, how many would you have at the end of six PCR cycles? A) 4 B) 64 C) 32 D) 16 E) 100 164) _____ 165) In gel electrophoresis, DNA molecules move toward the ________ electrode because they have an overall ________ charge. A) negative, negative B) negative, positive C) negative and positive, neutral D) positive, negative E) positive, positive 165) _____ 166) Which of the following procedures might be used to detect the presence of genetic sequences of a virus in a patient’s blood? A) Southern blotting B) xenotransplantation C) genome mapping D) electroporation E) creation of a gene library 166) _____ 167) A northern blot differs from a Southern blot in A) the size of the genetic sequences involved. B) the presence or absence of a nitrocellulose membrane. C) the type of nucleic acid being isolated. D) the number of genetic sequences detected. E) the type of probe used. 167) _____ 168) Which of the following methods of inserting DNA into cells might be used on plant seeds? A) protoplast fusion, injection, and electroporation B) protoplast fusion C) electroporation D) both injection and electroporation 168) _____ E) injection 169) The DNA double helix can be separated into single strands using A) both heat and NaOH. B) heat. C) heat, NaOH, and reverse transcriptase. D) NaOH. E) reverse transcriptase. 169) _____ 170) The sequencing and analysis of an organism’s genetic information is called A) genomics. B) protein synthesis. C) PCR. D) northern blotting. E) gene therapy. 170) _____ 171) Which of the following devices is used for PCR? A) a DNA sequencer B) a thermocycler C) a gene gun D) an electrophoresis chamber E) a nucleic acid synthesis machine 171) _____ 172) DNA fingerprinting can be used A) to detect unculturable organisms. B) in forensic investigations. C) to generate cDNA clones. D) for forensics and detection of unculturable organisms. E) to generate cDNA clones and libraries. 172) _____ 173) The process of introducing animal organs into the human body is A) electrophoresis. B) protoplast fusion. C) recombinant DNA technology. D) xenotransplantation. E) biotechnology. 173) _____ 174) Subunit vaccines are safer than traditional vaccines because A) they are acellular and can be administered in food. B) they are acellular and do not pose a risk for causing the disease. C) they are acellular. D) they do not pose a risk for causing the disease. E) they are administered in food. 174) _____ 175) Which of the following recombinant tools is NOT used in DNA fingerprinting? A) reverse transcription B) restriction enzyme digestion C) gel electrophoresis D) Neither PCR nor gel electrophoresis is used. E) PCR 175) _____ 176) Transgenic organisms 176) _____ A) contain cells from other organisms. B) have genomes that have been sequenced completely. C) contain genetically engineered microbes. D) are the same thing as clones. E) contain genes from other organisms. 177) Which of the following microbes produces a protein that kills a variety of insect pests? A) Pseudomonas B) Thermus aquaticus C) Haemophilus influenzae D) Plasmodium falciparum E) Bacillus thuringiensis 177) _____ 178) In vitro means A) “in life.” B) “within glassware.” C) “from a stranger.” D) “in the cell.” E) “within an organism.” 178) _____ 179) If all the following DNA fragments were analyzed on an electrophoresis gel, which one would migrate farthest from the negative electrode? A) 250 base pairs B) 5000 base pairs C) 750 base pairs D) 1000 base pairs E) 2500 base pairs 179) _____ 180) Protoplasts are associated with which of the following? A) Southern blotting B) electroporation C) xenotransplants D) gene therapy E) PCR 180) _____ 181) An antigen is A) a foreign substance that stimulates immunity. B) a genetic marker found in most plasmids. C) a naturally occurring insecticide. D) a substance used to make gels for DNA electrophoresis. E) a molecule necessary for PCR. 181) _____ 182) An effective tool for screening a large number of genetic sequences at once is known as A) cDNA synthesis. B) gel electrophoresis. C) microarray. D) restriction analysis. E) FISH. 182) _____ 183) Which of the following is generally NOT considered an ethical issue regarding recombinant DNA technology? A) answering basic research questions 183) _____ B) unforeseen impact on the environment C) screening of humans for genes that predispose them to disease D) the modification of crop plants E) the modification of animals to produce pharmaceuticals for humans 184) The first complete gene map was that of A) Escherichia coli. B) Staphylococcus aureus. C) Plasmodium falciparum. D) Pseudomonas. E) Haemophilus influenzae. 184) _____ 185) Which of the following microbes has been genetically engineered to contain a protein that helps protect crops from freezing? A) Salmonella B) Bacillus thuringiensis C) Escherichia coli D) Pseudomonas E) Deinococcus radiodurans 185) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Match the procedure with the appropriate tool or technique: A) Nitrocellulose membranes B) Reverse transcriptase C) Synthetic nucleic acids and radioactive chemicals D) DNA polymerase E) Agarose F) Single-stranded DNA and silicon chips G) DNA ligase H) Restriction enzymes I) Compressed air and gold beads J) Synthetic DNAs and fluorescent tags 186) Synthesis of cDNA 186) ____________ 187) Probes 187) ____________ 188) Cutting DNA molecules into fragments 188) ____________ 189) Microarray 189) ____________ 190) PCR 190) ____________ 191) Southern blotting 191) ____________ 192) FISH 192) ____________ 193) Injecting DNA into cells 193) ____________ 194) DNA electrophoresis 194) ____________ 195) Connecting DNA fragments 195) ____________ TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false. 196) Gene therapy for human genetic diseases has not been successful yet. 196) _____ 197) Reverse transcriptase synthesizes a DNA molecule from an RNA template. 197) _____ 198) Large DNA molecules such as chromosomes are easier to work with than small molecules. 198) _____ 199) Circular DNA molecules are generally more stable inside cells than linear molecules. 199) _____ 200) The number of DNA molecules produced during PCR increases exponentially. 200) _____ 201) Sticky-end fragments generated by EcoRI will hydrogen bond to any other sticky-end sequence. 201) _____ 202) Nitrocellulose membranes used in Southern blotting are more delicate than agarose gels. 202) _____ 203) Southern blotting is a technique that can be used to identify microbes that cannot be cultured. 203) _____ 204) DNA fingerprinting produces a unique banding pattern of DNA fragments for comparison with other DNA samples. 204) _____ 205) A subunit vaccine is prepared by extensive manipulation of the genome of the pathogen. 205) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Correct answers may contain more than one word. 206) ________ is the use of microbes to make practical products such as vaccines or hormones. 206) ____________ 207) ________ is used to detect the presence of a particular DNA sequence. 207) ____________ 208) Nucleic acid molecules used to deliver new genes to cells are called ________. 208) ____________ 209) ________, first isolated from bacterial cells, cut DNA molecules at specific sites. 209) ____________ 210) Short nucleic acid molecules used to locate complementary sequences in a larger population of molecules are called ________. 210) ____________ 211) A set of clones representing the entire genome of an organism is known as a(n) ________. 211) ____________ 212) The ________ is a technique used to detect specific RNA molecules in a larger population of molecules that has been separated by gel electrophoresis. 212) ____________ 213) ________ are sequences that bind to mRNA and genes to effect their function. 213) ____________ 214) The process of locating genes within the nucleic acid of an organism is called ________. 214) ____________ 215) ________ involves the insertion of foreign DNA directly into a cell’s nucleus using a glass micropipet. 215) ____________ 216) ________ can be used to detect mutant genes associated with genetic diseases in indi viduals before any clinical sympto ms are noted. 216) ____ ____ ____ 217) A ________ may be used to study the complex, changing patterns of mRNA production in an organism. 217) ____________ 218) ________, the biochemical precursor to vitamin A, can be added to rice by using recombinant DNA technology, thereby increasing its nutritional value. 218) ____________ 219) Study of the genome of ________ may provide insight into preventing or correcting genetic damage resulting from radiation. 219) ____________ 220) Vectors usually contain ________ such as antibiotic resistance genes or fluorescent tags. 220) ____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 221) Discuss some of the impacts that tools and techniques of recombinant DNA technology have had on medicine. 222) What is reverse transcriptase, and why is it an important tool of recombinant DNA technology? 223) Compare and contrast the two major types of restriction enzymes. 224) Compare and contrast the types of vectors used in recombinant DNA technology. 225) Explain what a transgenic organism is, and give two examples. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 226) Standard methods of sterilization are not effective in inactivating 226) _____ A) viruses. B) prions. C) bacterial cells. D) fungi. E) bacterial endospores. 227) Which of the following statements is true of disinfectants? A) Disinfectants are effective in destroying endospores. B) Disinfectants are used for sterilization. C) Disinfectants are used on inanimate surfaces. D) Disinfectants are used on living tissue. E) Disinfectants are only effective for short periods of time (seconds to minutes). 227) _____ 228) Which of the following statements concerning microbial death is FALSE? A) It is the permanent loss of a microbe’s ability to reproduce and can be used to evaluate antimicrobial agents. B) It can be used to evaluate the efficacy of antimicrobial agents. C) It is constant over time of exposure to an antimicrobial agent. D) It is not an effective means of evaluating the efficacy of antimicrobial agents. E) It is the permanent loss of a microbe’s reproductive ability. 228) _____ 229) Which of the following is an example of sanitization? A) A surgeon washes her hands before surgery. B) An autoclave is used to prepare nutrient agar. C) Heat is used to kill potential pathogens in apple juice. D) A public toilet is treated with disinfectants. E) A nurse prepares an injection site with an alcohol swab. 229) _____ 230) Aseptic means A) sanitized. B) sterile. C) clean. D) free of all microbes. E) free of all pathogens. 230) _____ 231) Which of the following would NOT be bacteriostatic? A) autoclaving B) freezing below 0°C C) desiccation D) refrigeration of mesophiles E) lyophilization 231) _____ 232) Antimicrobial agents that damage nucleic acids also affect A) the viral envelope. B) the cell membrane. C) endospores. D) protein synthesis. E) the cell wall. 232) _____ 233) Seventy percent alcohol is effective against A) enveloped viruses. B) prions. C) bacterial endospores. D) protozoan cysts. E) nonenveloped viruses. 233) _____ 234) An instrument that will come into contact with only the skin of a patient should be disinfected with a(n) A) low-level germicide. B) germistatic agent only. C) degerming agent only. D) high-level germicide. E) intermediate-level germicide. 234) _____ 235) Which of the following is NOT an effective means of sterilization? A) autoclaving B) incineration C) lyophilization D) ionizing radiation E) dry heat 235) _____ 236) Which of the following describes flash pasteurization? A) heating at 72°C for 15 seconds 236) _____ B) heating at 63°C for 30 minutes C) passing liquid through steam at 140°C D) heating at 72°C for 15 minutes E) heating at 134°C for one second 237) The dairy creamer used in restaurants is usually sterilized by A) UHT sterilization. B) ionizing radiation. C) lyophilization. D) filtration. E) autoclaving. 237) _____ 238) Boiling water for 10 minutes is effective in ridding it of A) both growing bacteria and enveloped viruses. B) protozoan cysts. C) bacterial endospores. D) actively growing bacteria. E) enveloped viruses. 238) _____ 239) Which of the following is NOT a feature associated with filtration? A) ability of some filters to trap viruses and proteins B) varying thicknesses of membrane filters used C) use of HEPA filters to filter air D) sterilization of heat-sensitive materials E) nitrocellulose or plastic membrane filters 239) _____ 240) Which of the following is a target of pasteurization? A) Neisseria gonorrhoeae B) Brucella melitensis C) Bacillus stearothermophilus D) Chlamydia trachomatis E) Clostridium botulinum 240) _____ 241) Which of the following types of radiation is nonionizing and has the shortest wavelength? A) X rays B) ultraviolet light C) infrared radiation D) gamma rays E) microwaves 241) _____ 242) Which of the following is used for microbial control in fresh fruits and vegetables? A) X rays B) microwaves C) gamma rays D) ultraviolet light E) electron beams 242) _____ 243) Which of the following can be used to disinfect air? A) ethylene oxide B) HEPA filters C) ultraviolet light D) both HEPA filters and ultraviolet light 243) _____ E) both ethylene oxide and ultraviolet light 244) Lysol is an example of which of the following groups of chemical antimicrobial agents? A) phenolics B) aldehydes C) halogens D) surfactants E) alcohols 244) _____ 245) Which of the following is the most appropriate pairing of microbe and biosafety level? A) Ebola, BSL-2 B) methicillin-resistant Staphylococcus aureus (MRSA), BSL-2 C) E. coli, BSL-3 D) anthrax, BSL-1 E) tuberculosis, BSL-1 245) _____ 246) Betadine is an example of which of the following groups of antimicrobial agents? A) halogens B) surfactants C) alcohols D) phenolics E) heavy metals 246) _____ 247) Which of the following statements about quaternary ammonium compounds is FALSE? A) They function by cross-linking proteins. B) They are harmless to humans except at high concentrations. C) They are a type of detergent. D) Zephiran is an example of a quat. E) They are not effective against Pseudomonas aeruginosa. 247) _____ 248) Which of the following is a sterilizing agent? A) peracetic acid B) ozone C) hydrogen peroxide D) ozone and hydrogen peroxide E) dish soap 248) _____ 249) Which of the following was used in the past to prevent the transmission of gonorrhea from an infected mother to her newborn? A) silver nitrate B) thimerosal C) hexachlorophene D) beta-propiolactone E) hydrogen peroxide 249) _____ 250) Which of the following is used to sterilize items that should not, or cannot, be exposed to heat or water? A) triclosan B) formaldehyde C) hydrogen peroxide D) calcium hypochlorite E) ethylene oxide 250) _____ 251) Which of the following statements about aldehydes is FALSE? A) They are usually hazardous to humans. B) Some aldehydes can sterilize after long periods of exposure. C) They denature proteins. D) They are used in aqueous solutions. E) They are used only to preserve dead tissues. 251) _____ 252) Disinfecting agents naturally produced by microorganisms are A) quats. B) triclosans. C) antimicrobials. D) halogens. E) aldehydes. 252) _____ 253) A chemical agent that kills pathogenic microbes in general is a(n) A) sanitizer. B) germicide. C) fungicide. D) antiseptic. E) disinfectant. 253) _____ 254) Which of the following is NOT a desirable characteristic of an ideal antimicrobial agent? A) It is inexpensive. B) It is harmless to humans. C) It only arrests growth of vegetative cells. D) It is stable during storage. E) It acts quickly. 254) _____ 255) The endospores of which of the following microbes are used to measure the effectiveness of autoclave sterilization? A) Mycobacterium bovis B) Pseudomonas aeruginosa C) Bacillus stearothermophilus D) Clostridium botulinum E) Neisseria gonorrhoeae 255) _____ 256) A scientist develops a new medication that is a protein compound and that must be administered by injection. Which of the following would be the most effective and safest means of preparing a sterile solution of the new medication? A) dilution with alcohol B) lyophilization C) filtration D) ultraviolet irradiation E) autoclaving 256) _____ 257) Which of the following procedures is currently the standard test used in the United States for evaluating the efficiency of antiseptics and disinfectants? A) thermal death point B) microbial death rate C) use-dilution test D) in-use test 257) _____ E) phenol coefficient 258) Which of the following would be used to sterilize a mattress? A) autoclaving B) ethylene oxide C) heavy metals D) formaldehyde E) radiation 258) _____ 259) Disinfectants that damage membranes include A) iodine. B) hydrogen peroxide. C) phenolics. D) alcohol. E) both alcohol and phenolics. 259) _____ 260) Which of the following antimicrobial agents is the most toxic to humans? A) ethylene oxide B) 70% alcohol C) quats D) iodophors E) chloramines 260) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Match the antimicrobial agent or method with the appropriate description: A) Disinfectant B) Sterilizing agent C) Both disinfectant and sterilizing agent 261) Filtration 261) ____________ 262) Hydrogen peroxide 262) ____________ 263) Incineration 263) ____________ 264) Alcohols 264) ____________ 265) Quats 265) ____________ 266) Ethylene oxide 266) ____________ 267) Glutaraldehyde 267) ____________ 268) Chlorine dioxide 268) ____________ 269) Gamma irradiation 269) ____________ 270) Boiling water 270) ____________ TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false. 271) An environment may contain some microbes and still be considered sterile. 271) _____ 272) Some viruses are inactivated by the same chemical or physical agents that damage cytoplasmic membranes. 272) _____ 273) UV light has the most effect on protein structure. 273) _____ 274) Antimicrobial agents usually work best at high temperatures and pH levels. 274) _____ 275) The phenol coefficient is one of the most widely used measurements of an antimicrobial agent’s effectiveness. 275) _____ 276) No chemical or antimicrobial agents inactivate prions. 276) _____ 277) The decimal reduction time is the time required to kill all the microbes in a given sample. 277) _____ 278) Slow freezing is more damaging to microbial cells than quick freezing. 278) _____ 279) Hydrogen peroxide is an effective antiseptic. 279) _____ 280) By themselves, soaps have only degerming activity, not antimicrobial activity. 280) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Correct answers may contain more than one word. 281) ________ is the process of freeze-drying microbes to preserve them. 281) ____________ 282) Natural antiseptics such as pine or clove oil are examples of antimicrobial compounds called ________. 282) ____________ 283) A(n) ________ is an iodine-containing organic compound found in such antiseptics as Betadine. 283) ____________ 284) Disinfectants known as ________ have the chemical group CHO, which reacts with and damages both proteins and nucleic acids. 284) ____________ 285) The lowest temperature that kills all cells in a broth in 10 minutes is known as the ________. 285) ____________ 286) The amount of time needed to sterilize materials using moist heat is ________ (greater than/less than) the time needed to sterilize using dry heat. 286) ____________ 287) A(n) ________ is an instrument that sterilizes by exposing materials to steam under pressure. 287) ____________ 288) The containment level ________ is appropriate when handling highly contagious deadly microbes. 288) ____________ 289) Ultraviolet light penetrates materials ________ (more effectively/less effectively) than gamma rays. 289) ____________ 290) ________ is a phenolic antimicrobial compound that has been incorporated into consumer items such as garbage bags and diapers. 290) ____________ 291) Elements such as iodine, chlorine, and bromine are examples of ________, which are the basis for many effective antimicrobial agents. 291) ____________ 292) Heavy metal and oxidizing agent disinfectants damage ________, interfering with microbial metabolism. 292) ____________ 293) The use of high levels of salt or sugar in the preservation of foods relies on the phenomenon of ________. 293) ____________ 294) The process of heating milk or fruit juice to levels that kill any pathogenic microbes present is known as ________. 294) ____________ 295) Sterilization procedures generally focus on inactivating or eliminating bacterial ________. 295) ____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 296) Some sterilization procedures do not kill all the microbes that may be present. Explain how these procedures can still be considered sterilization. 297) Describe the cellular structures or processes that can be targets of antimicrobial agents. 298) What is the in-use test, and why is it more useful than other methods of evaluating disinfectants? 299) Some physical methods of microbial control that work by removing microbes are just as effective as agents that kill or inhibit these microbes. Explain why this is so, and give some examples of these types of agents. 300) A student is shopping for antibacterial hand cleansers and is trying to decide which one to buy. One is a “waterless” hand gel containing 70% isopropanol, the second is an “antibacterial” hand soap containing triclosan (a phenolic), and the third is a wipe that lists benzethonium chloride (a synthetic quaternary ammonium salt) as the active ingredient. Compare and contrast these cleansers in terms of the action of the antimicrobial ingredient and the level of disinfection (degerming, germistatic, germicidal). MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 301) A large percentage of antibiotics and semisynthetic drugs are produced by members of the 301) _____ genus A) Mycobacterium. B) Streptomyces. C) Cephalosporium. D) Penicillium. E) Bacillus. 302) An antimicrobial that inhibits cell wall synthesis will result in which of the following? A) Cells cannot attach to their hosts. B) Ribosomes lose their function. C) Cells become more susceptible to osmotic pressure. D) The sterols in the cell wall become nonfunctional. E) The replication of cells, including cancer cells, slows down. 302) _____ 303) Beta-lactam antibiotics have an effect on which of the following types of cells? A) fungal cells B) virus-infected cells C) bacterial cells 303) _____ D) animal cells E) both animal and fungal cells 304) Which of the following is a primary advantage of semisynthetic drugs? A) They are less stable and consequently have fewer side effects. B) They are not readily absorbed, so they persist longer. C) They have a broader spectrum of action. D) They work faster. E) They must be administered intravenously. 304) _____ 305) Which of the following drugs specifically targets cell walls that contain arabinogalactan-mycolic acid? A) isoniazid B) bacitracin C) penicillin D) vancomycin E) methicillin 305) _____ 306) Which of the following antibiotics disrupts cytoplasmic membrane function? A) streptomycin B) amphotericin B C) tetracycline D) erythromycin E) penicillin 306) _____ 307) Which of the following is NOT a target of drugs that inhibit protein synthesis? A) movement of the ribosome from one codon to the next B) interference with alanine-alanine bridges C) the enzymatic site of the 50S ribosomal subunit D) the shape of the 30S ribosomal subunit E) the tRNA docking site 307) _____ 308) Which scientist coined the term antibiotic? A) Domagk B) Kirby C) Ehrlich 308) _____ D) Fleming E) Waksman 309) The most limited group of antimicrobial agents is the ________ drugs. A) anthelmintic B) antifungal C) antiviral D) antibacterial E) antiprotozoan 309) _____ 310) Another term for the Kirby-Bauer test is the A) E test. B) diffusion susceptibility test. C) broth dilution test. D) minimum inhibitory concentration test. E) minimum bactericidal concentration test. 310) _____ 311) Which of the following statements about the zone of inhibition is FALSE? A) It is measured as a diameter. B) It is measured after incubation. 311) _____ C) The larger the zone, the more resistant the organism is. D) It is a clearing zone with no growth. E) It is a result of diffusion of the drug out of the paper disk. 312) Which of the following groups of drugs can become incorporated into the bones and teeth of a fetus? A) aminoglycosides B) sulfonamides C) beta-lactams D) tetracyclines E) quinolones 312) _____ 313) Which of the following can result when antibiotic therapy disrupts the normal microbiota? A) thrush B) anaphylactic shock C) black hairy tongue D) pseudomembranous colitis E) both pseudomembranous colitis and thrush 313) _____ 314) Which of the following statements concerning development of antibiotic resistance is FALSE? A) Resistant cells are normally in the minority in a bacterial population. B) Resistant cells grow more efficiently and quickly than susceptible cells. C) Resistance can occur through mutation of existing bacterial genes. D) It is often mediated by R-plasmids. E) New resistance genes can be gained through transformation, transduction, or conjugation. 314) _____ 315) β-lactamase production is an example of which of the following types of resistance? A) removal of the drug via a pump B) change in the permeability of the drug C) overproduction of an enzyme in a key metabolic pathway D) inactivation of the drug E) alteration of the target of the drug 315) _____ 316) Probiotics A) is a term for resistance to antibiotics. B) involve microbial antagonism. C) are an alternative to the use of chemotherapy involving microbial antagonism. D) are an alternative to the use of chemotherapy. E) involve the use of extracts from microorganisms. 316) _____ 317) Most drugs that inhibit the synthesis of the cell wall act by A) preventing the formation of alanine-alanine bridges. B) blocking the secretion of cell wall molecules from the cytoplasm. C) disrupting the formation of the mycolic acid layer of the cell wall. D) preventing the formation of β-lactamases. E) preventing the cross-linkage of NAM subunits. 317) _____ 318) Most broad-spectrum antibiotics act by A) inhibiting protein synthesis. B) inhibiting metabolic pathways. C) inhibiting nucleic acid synthesis. D) disrupting the cytoplasmic membrane. 318) _____ E) inhibiting the synthesis of the cell wall. 319) Which of the following works by inhibiting ergosterol synthesis? A) amphotericin B B) turbinafine C) nystatin D) fluconazole E) both fluconazole and turbinafine 319) _____ 320) Sulfonamides A) are antimetabolic drugs. B) are no longer widely used. C) were the first widely used antimetabolic antimicrobial and indirectly inhibit nucleic acid synthesis. D) indirectly inhibit the synthesis of nucleic acids. E) were the first widely used antimicrobial drugs. 320) _____ 321) Which of the following pathways is specifically inhibited by sulfonamides? A) the conversion of tetrahydrofolic acid to PABA B) the conversion of PABA to dihydrofolic acid C) the conversion of dihydrofolic acid to PABA D) the conversion of dihydrofolic acid to tetrahydrofolic acid E) the conversion of PABA to tetrahydrofolic acid 321) _____ 322) Which of the following drugs inhibits nucleic acid synthesis specifically in prokaryotes? A) actinomycin B) quinolones C) tetracycline D) rifampin E) 5-fluorocytosine 322) _____ 323) The cooperative activity of drugs such as beta-lactam antibiotics and clavulanic acid, a β-lactamase inhibitor, is known as A) synergism. B) cross resistance. C) antimetabolism. D) chemotherapy. E) selective toxicity. 323) _____ 324) Alterations in the structure of which of the following are an important aspect of Gram-negative bacterial resistance to antimicrobial drugs? A) plasmids B) cytoplasmic membrane C) porins D) ribosomes E) mitochondria 324) _____ 325) It is inappropriate to prescribe antibacterial agents to treat colds or flu because A) these diseases are transmitted by endospores, which are hard to kill. B) these diseases are caused by viruses. C) these diseases exhibit cross resistance. D) the microbes involved can develop resistance rapidly. 325) _____ E) these diseases can act synergistically with each other. 326) Who discovered the first widely available antibiotic? A) Fleming B) Ehrlich C) Waksman D) Domagk E) Ehrlich and Waksman 326) _____ 327) Which of the following statements is true of selective toxicity? A) Selective toxicity takes advantage of structural differences between host and pathogen. B) Antimicrobial agents must target structural differences between host and pathogen and be more toxic to the patient than the pathogen. C) Selective toxicity takes advantage of metabolic differences between host and pathogen. D) To be effective, an antimicrobial agent must be more toxic to the patient than the pathogen. E) Selective toxicity takes advantage of structural and/or metabolic differences between host and pathogen. 327) _____ 328) Antimicrobials that block protein synthesis by binding to the mRNA are A) antisense nucleic acids. B) beta-lactams. C) aminoglycosides. D) macrolides. E) nucleic acid analogs. 328) _____ 329) The Etest determines which of the following? A) MBC B) MIC C) susceptibility D) both susceptibility and MIC E) both MBC and MIC 329) _____ 330) Which of the following is NOT a criterion by which all antimicrobial agents can be evaluated? A) their spectrum of action B) their activity against cell walls C) their efficacy D) their safety E) their route of administration 330) _____ 331) Which of the following interferes with cell wall synthesis by blocking alanine bridge formation? A) beta-lactams B) bacitracin C) vancomycin D) cycloserine E) both cycloserine and vancomycin 331) _____ 332) Antimicrobial sugar analogs are effective for A) blocking a metabolic pathway. B) preventing virus attachment. C) preventing cell membrane synthesis. D) preventing bacterial protein synthesis. E) preventing nucleic acid synthesis. 332) _____ 333) Which of the following is a measurement associated with the broth dilution test? A) lack of turbidity and zone of inhibition B) cell lysis C) the zone of inhibition D) presence of turbidity and cell lysis E) lack of turbidity 333) _____ 334) Infection of the ________ would be the hardest to treat with antimicrobial drugs. A) kidneys B) colon C) liver D) heart 334) _____ E) brain 335) Disruption of the normal microbiota can result in infections caused by which of the following microbes? A) Clostridium difficile B) Mycobacterium C) both Mycobacterium and Clostridium difficile D) Candida albicans E) Candida albicans, Mycobacterium, and Clostridium difficile 335) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Match the drug with its mode of action: A) Disruption of cytoplasmic membranes B) Inhibition of cell wall synthesis C) Inhibition of nucleic acid synthesis D) Inhibition of metabolic pathways E) Inhibition of protein synthesis 336) Quinolones 336) ____________ 337) Amphotericin B 337) ____________ 338) Vancomycin 338) ____________ 339) Tetracyclines 339) ____________ 340) Trimethoprim 340) ____________ 341) Erythromycin 341) ____________ 342) Methicillin 342) ____________ 343) Ribavirin 343) ____________ 344) Polymyxin 344) ____________ 345) Sulfonamides 345) ____________ TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false. 346) Paul Erhlich coined the term antibiotics for the “magic bullet” antimicrobials he pursued. 347) Antisense nucleic acids are designed to have no side effects against humans. 346) _____ 347) _____ 348) Beta-lactam drugs act by inhibiting formation of the cytoplasmic membrane. 348) _____ 349) Because all cells engage in protein synthesis, there are few antimicrobial drugs that selectively inhibit this process. 349) _____ 350) Many antimicrobial drugs that affect the cytoplasmic membrane are used only externally because they can be toxic to humans. 350) _____ 351) Some bacterial cells are resistant to a variety of antimicrobials because they actively pump the drugs out of the cell. 351) _____ 352) The outer membrane of Gram-negative bacteria enables many antimicrobial drugs to enter the cell more easily. 352) _____ 353) If a subculture of an MIC test grows in an MBC test, the concentration of the drug was bactericidal. 353) _____ 354) Brain and spinal cord infections are difficult to treat because most antimicrobial drugs cannot diffuse out of the blood into these organs. 354) _____ 355) Organs that are commonly affected by drug toxicity include the kidneys and the liver. 355) _____ SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Correct answers may contain more than one word. 356) Any drug that acts against a disease is called a(n) ________ agent. 356) ____________ 357) ________ means that a given antimicrobial agent is more toxic to a pathogen than to the host being treated. 357) ____________ 358) Antimicrobial agents that mimic the chemical structure of DNA building blocks are called ________. 358) ____________ 359) A(n) ________ drug is effective against a wide variety of pathogens. 359) ____________ 360) ________ are serious secondary infections that result from the killing of the normal microbiota. 360) ____________ 361) Competition between beneficial microbes and potential pathogens is called ________. 361) ____________ 362) A(n) ________ concentration of a drug is one at which microbes survive but are not able to grow and reproduce. 362) ____________ 363) Extrachromosomal pieces of DNA called ________ promote horizontal transfer of genes among bacteria and contribute to the spread of antimicrobial resistance. 363) ____________ 364) Some bacteria develop resistance to groups of drugs because the drugs are all structurally similar to each other; this is a phenomenon known as ________. 364) ____________ 365) ________ drugs are semisynthetic drugs developed to combat resistance against an existing drug. 365) ____________ 366) Drugs that slow down bacterial growth would be ________ to penicillin. 366) ____________ 367) External infections can be treated by ________ administration, in which a drug is applied directly to the site of infection. 367) ____________ 368) The abbreviation ________ stands for the smallest amount of a drug that will inhibit the growth and reproduction of a pathogen. 368) ____________ 369) Antiviral medications frequently block unique ________ to prevent production of new virus. 369) ____________ 370) Praziquantel alters the cytoplasmic membrane permeability of ________. 370) ____________ ESSAY. Write your answer in the space provided or on a separate sheet of paper. 371) Why can microbial resistance to antibiotics and other drugs be considered a primarily genetic phenomenon? 372) Discuss the cellular factors that might make a drug’s spectrum of action narrow rather than broad. 373) Explain the concept of selective toxicity. 374) Examine the diffusion susceptibility plate results shown in Figure 10.9. Propose an explanation for the appearance of the zone around the AM/10 disk, and discuss the implications for therapeutic use of this antibiotic for the pathogen tested. 375) Explain why many antibiotics are effective only against cells that are actively growing and reproducing. 1) A 2) D 3) B 4) E 5) C 6) B 7) D 8) C 9) D 10) A 11) D 12) E 13) A 14) E 15) A 16) B 17) C 18) D 19) D 20) B 21) D 22) A 23) D 24) D 25) B 26) C 27) B 28) D 29) C 30) C 31) D 32) B 33) C 34) B 35) B 36) D 37) C 38) A 39) B 40) B 41) B 42) D 43) A 44) E 45) C 46) FALSE 47) FALSE 48) TRUE 49) TRUE 50) FALSE 51) TRUE 52) FALSE 53) FALSE 54) TRUE 55) TRUE 56) nitrogen fixation 57) Chemoheterotrophs 58) superoxide 59) optimum 60) mesophiles 61) Alkalinophiles 62) crenation 63) inoculum 64) pure culture 65) Agar 66) lag 67) growth curve 68) Flow cytometry 69) pellicle 70) spectrophotometer 71) Oxygen is toxic to organisms only because of the highly reactive alternative forms of the molecule. These forms of oxygen can accumulate in cells and damage them by oxidizing key cellular molecules and structures. To tolerate the presence of oxygen (to allow aerobic cellular respiration to take place), cells must have ways of converting these toxic forms of oxygen to less harmful molecules. Cells use a variety of enzymes to accomplish this. These enzymes are superoxide dismutase (for elimination of the superoxide radical) and catalase and peroxidase (for the removal of hydrogen peroxide from cells). By continuous use of these enzymes, aerobic cells can use oxygen in their metabolism without suffering too many of the adverse effects of oxygen. Likewise, one major reason obligate anaerobes cannot tolerate any oxygen in their environment is the absence or reduced activity of such enzymes in those cells. 72) All microbes have particular ranges of temperature and pH within which they exist. When the temperature or pH of their environment falls outside this range, their growth is inhibited, and they may even die as a result of the adverse conditions. Therefore, only those microbes whose pH and temperature requirements match those conditions found in the human body will be able to grow and reproduce there. For example, because the temperature of the human body is 37°C, only mesophiles can reproduce there. In addition, the pH of most tissues and fluids in the body is 6.5—7.5, which matches the pH requirements of neutrophiles. Therefore, it is not surprising that most human pathogens are mesophiles and neutrophiles. However, this is not always the case. Some microbes have adapted to environments that would otherwise be extremely hostile to most microbes. A good example is the bacterium Helicobacter pylori, which is able to live in the extremely acidic conditions of the stomach by secreting substances that help to neutralize the acid. The result is an infection that can lead to stomach ulcers. 73) The streak-plate and the pour-plate methods of bacterial isolation are both used to produce pure cultures of bacteria from specimens. Both techniques involve the use of agar-based growth media contained in Petri plates. Additionally, both techniques involve the use of dilutions as a means of isolating single cells or groups of cells that then grow into isolated colonies. However, there are several significant differences between the two techniques. The main difference is the way in which the specimen is diluted. In the streak-plate method, the specimen is diluted by use of an inoculating loop that spreads organisms over the surface of the agar. Thus, colonies appear only on the agar surface. In the pour-plate method, however, dilutions of the specimen are made in tubes of broth and then each dilution is added to melted agar, which is then poured into Petri dishes. Thus, microbes are mixed throughout the agar, and colonies will appear both in and on the medium. 74) Previous estimates of microbial diversity were largely based on the ability to detect microbes in samples handled in a typical laboratory setting. In most cases, laboratory conditions represent a narrow range of growth parameters, including temperature range, oxygen and other gas levels, and spectrum of nutrients. Even in cases where attempts are made to simulate the normal conditions for microbes (e.g., providing a high-pressure environment for organisms collected from hyperbaric environment), microorganisms must frequently tolerate fluctuations in the grow or even exposure to extremely adverse conditions for short periods of time. Organisms that are intolerant of th significant fluctuation in their environmental requirements do not survive transport to the lab to be measured or envir cultured. As a consequence, only the relatively few microbes that are versatile in their nutrient requirements and onm can tolerate fluctuations in their growth environment have been observed or isolated in the laboratory. This, in turn, ent resulted in misleadingly low estimates of microbial diversity. 75) Direct methods of measuring microbial growth involve quantifying the number of microbes in a specimen through actual counting of cells in a microscope or cytometer or counting the numbers of colonies produced from the plating of a specimen. The advantage of these techniques lies in their usefulness for counting very large and very small populations of bacteria. Indirect methods, by contrast, seek to quantify cells by measuring some characteristic related to the number of cells present. For example, spectrophotometry measures the amount of light transmitted through a culture; the less light that is transmitted, the more cells are present. The amount of light transmitted gives an approximation of the number of cells present. Indirect methods are useful for quantifying microbes, such as filamentous microbes, that are hard to count directly. Both direct and indirect methods seek to arrive at an approximation of the actual number of cells present. Because that number is changing even during the measurement process, neither technique can give an exact number of cells. 76) B 77) A 78) D 79) A 80) C 81) E 82) C 83) B 84) B 85) E 86) C 87) E 88) A 89) C 90) A 91) C 92) C 93) E 94) E 95) A 96) D 97) E 98) A 99) B 100) E 101) D 102) E 103) D 104) E 105) D 106) A 107) A 108) E 109) E 110) C 111) A 112) C 113) B 114) B 115) A 116) C 117) C 118) A 119) B 120) C 121) FALSE 122) FALSE 123) TRUE 124) FALSE 125) TRUE 126) TRUE 127) FALSE 128) TRUE 129) TRUE 130) FALSE 131) gene 132) euchromatin 133) transduction 134) auxotroph 135) topoisomerase 136) nucleotide analog 137) frameshift 138) anticodon 139) A site 140) triphosphate deoxyribonucleotides 141) operon 142) leading strand 143) genotype 144) promoters 145) Pre-messenger 146) DNA replication and transcription are similar processes in that they both involve the production of molecules of nucleic acids using a preexisting template. Therefore, they both involve the polymerization of nucleotides to create long chains, as well as the utilization of complementary base-pairing rules to create the nucleotide sequence of the new molecule based on the sequence of the template. Additionally, these chains of nucleotides are synthesized in the same direction, 5′ to 3′, regardless of the type of nucleic acid being produced. However, there are a number of differences between these two processes as well. The product of DNA replication is an exact, complete DNA copy of an entire DNA molecule that will be passed on to the offspring of the cell producing it. The product of transcription is an RNA copy of a limited region (a gene) of a DNA molecule. Furthermore, this RNA molecule may not be an exact copy of the gene, because transcription is more prone to errors than DNA replication. The RNA molecules produced during transcription are used within the cell that produces them to provide information for the synthesis of proteins during translation. 147) All cells possess one or more DNA molecules that serve as the genetic blueprint of the cell; these molecules are generally referred to as chromosomes. Prokaryotic chromosomes differ from eukaryotic chromosomes in their number and physical shape. Eukaryotic chromosomes tend to be more complex in their organization, involving specialized packaging proteins called histones. Eukaryotic cells also tend to contain more chromosomes than prokaryotes, which have no more than two chromosomes. In addition, all cells contain additional nucleic acid in the form of various types of RNA (mRNA, tRNA, primer RNA, siRNA, RNAi, and rRNA), which are used to assist in the cell’s genetic processes. Most cells contain other types of nucleic acid, such as plasmids or the DNA found in organelles such as mito chloroplasts. Plasmids are a common form of prokaryotic DNA and confer a variety of special abilities to the cell, chon depending on the specific genes carried by the plasmid. Some eukaryotic cells may also contain plasmids. The DNA dria of eukaryotic mitochondria and chloroplasts is used to partially control the activities of these organelles in and conjunction with genes found in the cell’s nucleus. 148) The eukaryotic transcript is extensively modified after transcription and must be transported out of the nucleus before it is translated. Prokaryotic transcripts are not extensively modified before translation, and translation can be initiated before transcription is completed. One result of these differences is that regulated protein products are produced more promptly in prokaryotes than in eukaryotes, allowing prokaryotes to respond to environmental change much more quickly. Eukaryotes have multiple RNA polymerases for transcription and a larger variety of transcription initiation factors. As a consequence, gene regulation is potentially more complex in eukaryotes than in prokaryotes. 149) Both the lactose and the tryptophan operons have certain features in common. They both contain a set of genes dedicated to a common purpose (such as the catabolism of lactose by the genes of the lactose operon) and regulatory elements such as a promoter and an operator. Each of these operons makes use of a repressor protein, which binds to the operator region and alters the activity of the operon. However, the lactose operon is classified as an inducible operon, which means it requires an inducer (lactose itself) in order to be activated. In the absence of the inducer, the repressor protein shuts down the operon. In contrast, the tryptophan operon is a repressible operon, which requires a corepressor (tryptophan itself) in order to activate the repressor and shut down the operon. In the absence of the corepressor and repressor, the operon is fully functional. In both types of operons, the molecule either catabolized (in the case of lactose) or synthesized (in the case of tryptophan) is an important component of the regulation of the operon. In this way, the cell maintains precise control over these genetic pathways and does not spend time and energy making enzymes that are not needed. For example, making enzymes to catabolize lactose when no lactose is present would waste energy and metabolites. 150) A point mutation is a single base change in the nucleotide sequence of a cell’s genome. The effects of a point mutation can depend on its location. Point mutations in noncoding regions of the genome are usually harmless. Even in coding regions, point mutations can be harmless if they result in silent mutations. Silent mutations preserve the sense of the amino acid code because of the concept of “wobble,” in which two codons can code for the same amino acid by varying only at the third base of the codon. If the point mutation has occurred at this third base, then the amino acid sequence of the protein will remain unchanged. Point mutations occurring at the first or second base of the codon are almost always much more serious because they change the codon to a completely different amino acid. This type of point mutation is known as a missense mutation. (The only exception to this occurs when the new amino acid is chemically similar to the previous amino acid, in which case the missense mutation usually causes little or no change in the overall structure or function of the protein.) Finally, one of the most serious types of point mutations is a nonsense mutation in which the codon has been changed to a stop codon. These types of mutations result in the abnormal termination of a protein sequence. In all such cases, if the protein affected by the mutati on is an enzyme or some other vital protein required for proper cellular function, then the cell and/or organism may die as a result of these relatively simple mutations. 151) A 152) E 153) A 154) C 155) C 156) B 157) C 158) B 159) A 160) C 161) E 162) C 163) A 164) B 165) D 166) A 167) C 168) E 169) A 170) A 171) B 172) D 173) D 174) B 175) A 176) E 177) E 178) B 179) A 180) B 181) A 182) C 183) A 184) E 185) D 186) B 187) C 188) H 189) F 190) D 191) A 192) J 193) I 194) E 195) G 196) FALSE 197) TRUE 198) FALSE 199) TRUE 200) TRUE 201) FALSE 202) FALSE 203) TRUE 204) TRUE 205) FALSE 206) Biotechnology 207) Southern blot 208) vectors 209) Restriction enzymes 210) probes 211) gene library 212) northern blot 213) Antisense RNA 214) genetic mapping 215) Microinjection 216) Genetic screening 217) DNA microarray 218) Beta-carotene 219) Deinococcus radiodurans 220) genetic markers 221) Human gene libraries and DNA sequencing have greatly facilitated detecting genes and gene complexes that contribute to disease, both the genetic mutations that cause disease and genetic predispositions to a wide range of diseases. PCR, FISH, and microarrays are all tools that can be used to determine whether a person carries a specific genetic variation linked to disease or to detect the presence of a pathogen causing disease. Recombinant technology has provided tools to prevent or cure disease. Some examples include the ability to produce therapeutic agents such as humulin for diabetes, clotting factors for people with blood-clotting disorders, and vaccines to prevent infection. The use of gene therapy to correct disorders of abnormal or nonfunctional genes is in its infancy but holds great promise. 222) Reverse transcriptase is an enzyme produced by retroviruses. This enzyme allows these viruses to carry out their unique life cycle, which involves the production of double-stranded DNA molecules from an RNA template. This activity is exploited in the lab to produce cDNA molecules from mRNA isolated from a cell. cDNA is a useful molecule because it does not contain any intron sequences normally present in eukaryotic genes; it essentially represents the genetic information in its “final form” from the viewpoint of the cell. Thus, cDNA is ideal for expressing human (or eukaryotic) genes in bacteria because all of the RNA processing (which is unique to eukaryotes) has already been done. 223) All restriction enzymes recognize specific sequences in DNA molecules and cut at those sequences, making them powerful tools for generating and manipulating DNA fragments. However, these enzymes differ in the type of cut they make. One type of cut is a staggered cut, which produces complementary overhangs known as “sticky ends.” These ends can base pair with each other (if they have the same sequence), and they allow DNA fragments to be joined relatively easily. The other type of cut occurs at the same place on each strand of DNA and produces “blunt ends.” Fragments with this type of end do not base pair with each other at all, making the joining of these fragments more difficult than sticky-ended fragments. However, blunt ends are more “generic” than sticky ends; they allow two fragments to be joined no matter which restriction enzyme generated them (as long as they were generated by blunt-end cutters). 224) All vectors have certain things in common. They are small enough to be easily manipulated, and they are able to survive for long periods of time inside cells. Also, they usually contain genetic markers that help identify the cells that receive the vector. However, there are different types of vectors available. Bacterial plasmids are commonly used, but they are limited in the size of the genes they can carry. Transposons and viruses can also be used as vectors. They have the advantages of being able to carry large amounts of DNA and to integrate themselves into the chromosome of the cell, making them some of the most stable types of vectors. 225) A transgenic organism is one that contains genes from other organisms. These genes usually add some special ability or function to the organism. Agriculture offers many examples of transgenic organisms. Soybeans have been engineered to contain glyphosate-resistance genes, and other crops have been engineered to grow well in soil with high salt concentrations. Still other plants have been engineered to contain the gene for Bt toxin, a bacterial toxin that kills insect pests that would otherwise feed on and destroy the crop. Not all transgenic organisms represent such extreme genetic modifications, however. Some genetically modified organisms simply represent efforts to improve nutritional content (in the case of plant crops) or to increase food yield (in the case of bovine growth hormone, which is produced by transgenic bacteria and then given to cattle to increase their meat and milk yield). 226) B 227) C 228) D 229) D 230) E 231) A 232) D 233) A 234) A 235) C 236) A 237) A 238) A 239) B 240) B 241) B 242) C 243) D 244) A 245) B 246) A 247) A 248) A 249) A 250) E 251) E 252) C 253) B 254) C 255) C 256) C 257) C 258) B 259) E 260) A 261) B 262) C 263) B 264) A 265) A 266) B 267) C 268) A 269) B 270) A 271) TRUE 272) TRUE 273) FALSE 274) FALSE 275) FALSE 276) FALSE 277) FALSE 278) TRUE 279) FALSE 280) TRUE 281) Lyophilization 282) phenolics 283) iodophor 284) aldehydes 285) thermal death point 286) less than 287) autoclave 288) BSL-4 289) less effectively 290) Triclosan 291) halogens 292) proteins 293) osmotic pressure 294) pasteurization 295) endospores 296) Theoretically, sterilization is the complete removal or destruction of all microbes in a particular environment. These include dormant forms of microbes, such as bacterial endospores. However, from a practical standpoint, one must take other factors into account when deciding what is or is not sterile. For example, the particular application of the sterilized material must be considered. Although there may be hyperthermophilic microbes present in canned foods after sterilization, they cannot grow and divide at normal shelf temperatures; thus, their presence does not cause problems. In practice, only those microbes that would cause problems either by their presence or by their continued growth and reproduction are generally the targets of sterilization methods. When these microbes have been eliminated, the goal of sterilization can be said to have been reached. 297) In general, there are two types of cellular targets for antimicrobial agents. One type of target is the variety of cellular molecules and structures that make up the cell. These include such structures as the cytoplasmic membrane and the cell wall, either of which can be damaged by various types of antimicrobial agents. When these structures are damaged, the cell loses control over the entry and exit of molecules, or it succumbs to the forces of osmotic pressure on its overall structure. The disruption of the cell’s osmotic balance due to problems with the cell wall or cell membrane can disable virtually all cellular chemical reactions, because most of them depend on water. Proteins and nucleic acids can also be a target of antimicrobial agents, which directly alter these molecules either by denaturation, in the case of proteins, or by mutation, in the case of DNA molecules. Damage to these types of targets impairs the ability of the cell to function. Denaturation of enzymes can disrupt a variety of metaboli c pathways, which, in turn, can inhibit the growth of the cell or even kill it. Mutations in DNA molecules can influence metabolic pathways and other cellular functions and may be extensive enough that the microbe ceases to function (dies). 298) The in-use test is a method of evaluating antimicrobial agents such as disinfectants or antiseptics. It involves collecting specimens from objects that need to be disinfected, both before and after the disinfecting agent is applied. Then the specimens are inoculated into growth media, and the presence or absence of growth is an indicator of the effectiveness of the agent. The in-use test is regarded as an informative and useful test because it makes use of microbes that are actually found in the area of concern, and it gives a “real-life” picture of how the antimicrobial agent will work in that situation. Conversely, other tests, such as the disk-diffusion test or the use-dilution test, are not as useful because they rely on standardized conditions in a laboratory environment, using test microbes that may or may not have any relation to the actual microbes that need to be targeted by the antimicrobial agent. Additionally, in some environments, many microbes form biofilms that can affect the activity of an antimicrobial agent, and these biofilms are not normally present in standardized testing procedures. Therefore, although the in-use test is not as convenient or quick as the other types of tests, it is regarded as more useful. 299) In some antimicrobial applications, the ability to remove microbes is just as good as, if not better than, killing or inhibiting their growth. The reason is that microbes such as bacteria can cause problems by their mere presence in a particular environment because of their ability to grow and divide rapidly. The removal of a microbe automatically eliminates its growth. Microbes can be mechanically removed from a particular environment in two ways: by filtration or by the use of chemical compounds such as soaps. Filtration involves the use of membranes with small pores that trap relatively small bacterial cells and, in some cases, even viruses. The liquid that passes through the filter is then free of these microbes and can be considered sterile. Soaps are examples of surfactants, molecules that have hydrophobic and hydrophilic regions. Soaps are thus able to interact with both water molecules and oily material, which usually contains the target microbial cells. The result is that soaps can disinfect by a process of degerming, which is the physical removal of microbes from an environment, such as the hands. 300) All three are germicidal, although not all to the same degree. The alcohol of the waterless hand cleaner is a germicide that disrupts cytoplasmic membranes and denatures proteins. It is not effective against bacterial endospores or fungal spores, and it has limited effect on nonenveloped viruses. The alcohol evaporates quickly, so the germicidal effect is short term. The waterless hand cleaner is an inter not an effective degermer. medi The hand soap contains a phenolic, which also damages cytoplasmic membranes and denatures proteins, and is ate-l effective on the same range of microbes as the alcohol. Phenolics are intermediate-level disinfectants that persist on evel surfaces for long periods of time, providing extended disinfection. If used with running water and the hands are disin vigorously rubbed, the hand soap can be an effective degermer. fecta Synthetic “quats” (quaternary ammonium compounds) disrupt cell membranes. They are effective against fungi, nt enveloped viruses, and most bacteria, but not against nonenveloped viruses, nor on endospores. Quats are and low-level disinfectants that are germicidal for some microbes. The action of using and discarding the wipe provides is some degerming effect. 301) B 302) C 303) C 304) C 305) A 306) B 307) B 308) E 309) C 310) B 311) C 312) D 313) E 314) B 315) D 316) C 317) E 318) A 319) E 320) C 321) B 322) B 323) A 324) C 325) B 326) D 327) E 328) A 329) D 330) B 331) E 332) B 333) E 334) E 335) E 336) C 337) A 338) B 339) E 340) D 341) E 342) B 343) C 344) A 345) D 346) FALSE 347) TRUE 348) FALSE 349) FALSE 350) TRUE 351) TRUE 352) FALSE 353) FALSE 354) TRUE 355) TRUE 356) chemotherapeutic 357) Selective toxicity 358) nucleotide analogs 359) broad-spectrum 360) Superinfections 361) microbial antagonism 362) bacteriostatic 363) R-plasmids 364) cross resistance 365) Second-generation 366) antagonistic 367) topical 368) MIC 369) enzymes 370) parasitic worms 371) Microbial resistance is considered a genetic phenomenon because there are two major ways that bacteria acquire resistance: through mutations of chromosomal genes or through acquisition of new genes carried on R-plasmids. In both cases, the cell gains the ability to resist the activity of a particular drug through the modified structure or activity of proteins that are coded for by the genes in question. For example, some of these altered proteins can be cytoplasmic membrane proteins or porin proteins that no longer allow a drug such as penicillin to enter the cell. Also, some of the proteins coded for by these genes may be enzymes of various sorts that serve to inactivate a particular drug, such as the inactivation of beta-lactam antibiotics by β-lactamases. Furthermore, these altered genes and proteins are then heritable by the offspring of the cell that acquired the resistance, leading quickly to entire populations of bacteria or other microbes that are resistant to a drug. When selective pressure is then brought to bear (through the administration of a particular drug) on a population that contains both susceptible and resistant cells, the result is that the susceptible cells die off, leaving the resistant cells to grow and flourish. 372) When a drug is labeled “narrow-spectrum,” meaning that it has activity against only a limited number of microbes, generally the reason is that many microbes possess some form of natural resistance against the drug. For example, many drugs work better against Gram-positive organisms than Gram-negative ones because Gram-negative cells possess an outer membrane that does not allow these drugs to enter the cell as readily as they enter Gram-positive cells. Other cellular factors that can have an effect on the spectrum of action of a particular drug include the presence of R-plasmids in the cell that carries resistance genes, the presence of altered cytoplasmic membrane or cell wall proteins that prevent the passage of some types of drugs, and alterations in a cell’s metabolic pathways, which can make the cell more resistant to certain types of drugs. Other antimicrobials have a narrow spectrum of action because they target a metabolic or structural feature unique to a single pathogen or small group of pathogens. One example of this type of narrow-spectrum antimicrobial is antisense RNA, which complements a specific nucleotide sequence that may be present in only one pathogen. 373) Selective toxicity is the underlying principle supporting Ehrlich’s idea of the “magic bullet.” This simply means that the most effective antimicrobial drugs are those that target some difference in a cellular structure or metabolic proc patient cell and the target microbe. Conversely, the more similar the host cell and the microbe are, the harder it is to ess selectively attack just the microbe. Drugs that do not differentiate very well between types of cells are generally betw more toxic to the host than those that are more selective. This is most striking in the case of antiviral drugs, which een are generally poor magic bullets because the virus is dependent on the host cell for all aspects of its growth. Those the drugs that successfully inactivate the virus sometimes also end up damaging or even killing the cell. host/ 374) The ring of colonies within the outermost limit of the zone of inhibition indicates that there are some cells in the population that are less susceptible to the antibiotic than the rest. If this antibiotic were used to treat an infection with this population, the growth of bacteria with some resistance would be promoted at the expense of the more susceptible cells, potentially giving rise to a new variant that is fully resistant. If this were to occur in a patient being treated, the antibiotic therapy would fail, putting the patient’s health at risk. Therefore drug AM would be a poor choice, perhaps the poorest choice, for chemotherapy against this bacterial species. 375) When cells are not actively growing and reproducing, they are not synthesizing many of their component molecules or structures. Because many antimicrobial drugs inhibit the synthesis of structures such as the cell wall or interfere with various metabolic pathways, cells that are not actively doing one or both of these activities will be naturally more resistant to these drugs. For example, as bacterial cells age or become dormant, they cease to synthesize molecules such as peptidoglycan; therefore, drugs such as penicillin, which act by inhibiting peptidoglycan synthesis, have no effect on these cells. Additionally, as cells age, they may modify or cease certain metabolic pathways. Drugs that target these pathways will thus lose their effect.