Exam 1 Test Files

Question 1

What unique mechanism for transferring antibiotic resistance genes could occur at relatively high frequency for a
gene on a bacterial chromosome adjacent to a phage genome insertion site?
□ A: conjugation
□ B: transduction
□ C: transposition
□ D: integrin transfer □ E: transformation

Answer 1

□ B: transduction

Question 2

n testing antibiotic A by the disk diffusion assay, bacterium X has an inhibition zone of 10 mm. See the chart relating inhibition zone and antibiotic concentration. The drug safely achieves a concentration of 64-128 micrograms per milliliter in the human body. Which of the following is true?
□ A: The antibiotic will be effective against bacterium X in a patient
□ B: The antibiotic will be ineffective against bacterium X in a patient
□ C: It is not possible to tell from the above information if the antibiotic will be effective or not in a patient
□ D: The antibiotic will be effective at all concentrations >16 micrograms per milliliter in a patient
□ E: The antibiotic will be effective at all concentrations below 128 micrograms per milliliter in a patient

Answer 2

□ B: The antibiotic will be ineffective against bacterium X in a patient

Question 3

Which anti-mycobacterial antibiotic acts by inhibiting the attachment of mycolic acid to the cell wall?
□ A: Metranidazole 
□ B: Isoniazid
□ C: Ethambutol 
□ D: Cycloserine
□ E: Trimethoprim

Answer 3

□ C: Ethambutol

Question 4

4 What is a common mechanism of bacterial resistance to tetracyclines?
□ A: hydrolysis of -lactam ring by -lactamase
□ B: drug-resistant dihydrofolate reductase
□ C: drug-resistant dihydropteroate synthase
□ D: methylation of 23S rRNA
□ E: activation/acquisition of a drug efflux pump

Answer 4

□ E: activation/acquisition of a drug efflux pump

Question 5

Import of glucose into bacterial cells
□ A: uses a permease to facilitate movement of glucose across the plasma membrane
□ B: involves chemical alteration of glucose as part of the transport process
□ C: only occurs if the glucose can move passively down a concentration gradient
□ D: uses a proton gradient in the import process
□ E: requires a siderophore

Answer 5

□ B: involves chemical alteration of glucose as part of the transport process

Question 6

Which oral bacteria are facultative anaerobes?
□ A: Aggregatibacter spp. 
□ B: Neisseria spp.
□ C: Eubacterium spp.
□ D: Streptococcus spp.
□ E: Propionibacterium spp.

Answer 6

□ D: Streptococcus spp.

Question 7

Which of the following elements is often required as a cofactor for specific enzymes?
□ A: carbon
□ B: phosphorus 
□ C: sulfur
□ D: nitrogen
□ E: zinc

Answer 7

□ E: zinc

Question 8

Which is an example of a bacterial genus whose members require a complex nutrient source such as blood agar
for growth in the laboratory? 
□ A: Chlamydia
□ B: Pseudomonas
□ C: Streptococcus
□ D: Lactobacillus □ E: Escherichia

Answer 8

□ C: Streptococcus

Question 9

A cell has abundant levels of tryptophan and, as a consequence, stops transcription of genes for tryptophan
biosynthesis through the binding of a protein to the operator site adjacent to these genes. This is an example of
□ A: attenuation
□ B: allosteric regulation
□ C: gene repression by a corepressor
□ D: gene induction by an inducer □ E: group translocation

Answer 9

□ C: gene repression by a corepressor

Question 10

Fimbriae
□ A: are numerous (up to 1000/cell) short, thin, hairlike, proteinaceous appendages on a bacterial cell s surface
□ B: are long, thick, proteinaceous appendages on a bacterial cellʝs surface numbering only 1-10/cell
□ C: are networks of polysaccharides that coat bacterial cells
□ D: provide bacteria protection from osmotic stress
□ E: are composed of substructures called a filament, a basal body, and a hook

Answer 10

□ A: are numerous (up to 1000/cell) short, thin, hairlike, proteinaceous appendages on a bacterial cell s surface

Question 11

Which is a property of saliva?
□ A: salivary components are similar to serum within the blood stream
□ B: salivary components compete with bacteria for binding tooth surfaces
□ C: salivary components promote aggregation of bacteria
□ D: saliva causes large pH changes in oral cavity
□ E: saliva is the main source of neutrophils in oral cavity

Answer 11

□ C: salivary components promote aggregation of bacteria

Question 12

What component is only found in gram-positive bacteria?
□ A: Braun s lipoprotein 
□ B: lipopolysaccharide
□ C: flagella
□ D: peptidoglycan
□ E: capsule

Answer 12

□ A: Braun s lipoprotein

Question 13

What is false about the cells growing on the petri dish in step 7 of the scheme depicted in figure 4-3?
□ A: they contain one or more Yersinia pseudotuberculosis genes
□ B: they contain a complete E. coli genome
□ C: they are bacteria that had invaded the mammalian cells
□ D: they are bacteria that contain an insertion mutation
□ E: they are bacteria that can be killed if exposed to gentamycin

Answer 13

□ D: they are bacteria that contain an insertion mutation

Question 14

What is a property of a bacterial slime layer? protects a bacterium from viral infection or predation by other
bacteria and is typically composed exclusively of polysaccharides?
□ A: typically composed of lipids
□ B: typically composed of proteins
□ C: typically composed of chains of N-acetylglucosamine plus N-acetylmuramic acid
□ D: typically composed of polysaccharides
□ E: typically composed of nucleic acids

Answer 14

□ D: typically composed of polysaccharides

Question 15

What is a false statement about the bacterial component of a typical human microbiome?
□ A: there are 10 times more bacterial cells than human cells
□ B: bacteria comprise up to ~3% of a person’s body weight
□ C: these bacteria interfere with our immune system’s ability to recognize pathogenic bacteria
□ D: we begin acquire these bacteria after birth
□ E: these bacteria are not typically present in cerebrospinal fluid

Answer 15

□ C: these bacteria interfere with our immune system’s ability to recognize pathogenic bacteria

Question 16

What is the most likely example of an exogenously acquired disease?
□ A: HIV/AIDS acquired in utero
□ B: common cold from a rhinovirus infection
□ C: staphylococcal infection from a cut in the skin
□ D: pneumonia from microaspirations of Pneumococcus bacteria
□ E: uninary tract infection by E. coli

Answer 16

□ B: common cold from a rhinovirus infection

Question 17

Why is “gentle lysis” used for in step 6 of the scheme depicted in figure 4-3?
□ A: to kill E. coli cells that are present outside of mammalian cells
□ B: to select for E. coli cells that contain a suicide plasmid
□ C: to liberate E. coli cells that are present inside of mammalian cells
□ D: to select for E. coli cells that contain a transposon insertion □ E: to promote the invasion of mammalian cells by E. coli

Answer 17

□ C: to liberate E. coli cells that are present inside of mammalian cells

Question 18

1/1
18 Where in the oral cavity would you expect to find the largest numbers of
neutrophils? 
□ A: saliva
□ B: dorsum of tongue
□ C: buccal mucosa
□ D: gingival crevicular fluid
□ E: where dental appliances contact
teeth

Answer 18

□ D: gingival crevicular fluid

Question 19

What component of bacterial cells is most significant in conferring cell shap etc.)?
□ A: plasma membrane
□ B: lipopolysaccharrides
□ C: peptidoglycan layer
□ D: capsule
□ E: inclusion bodies

Answer 19

□ C: peptidoglycan layer

Question 20

What is the main phosphorus source for bacteria?
□ A: amino acids
□ B: ammonia
□ C: glucose-6- phosphate
□ D: phosphoenolpyruvate (PEP)
□ E: inorganic phosphate

Answer 20

□ E: inorganic phosphate

Question 21

20 Which molecules anchor the peptidoglycan layer to the plasma membrane of gram positive bacteria?
□ A: lipoteichoic acids
□ B: siderophores
□ C: lipopolysaccharides
□ D: hopanoids
□ E: Braun's lipoproteins

Answer 21

□ A: lipoteichoic acids

Question 22

Which oral bacteria require significant amounts of carbon dioxide for opti growth?
□ A: Capnocytophaga spp. 
□ B: Neisseria spp.
□ C: Eubacterium spp.
□ D: Veillonella spp.
□ E: Actinomyces spp.

Answer 22

□ A: Capnocytophaga spp.

Question 23

Which of the following are cholesterol-like molecules present in bacterial membranes?
□ A: teichoic
acids
□ B: siderophores
□ C: lipopolysaccharides
□ D: hopanoids 
□ E: Braun's
lipoproteins

Answer 23

□ D: hopanoids

Question 24

What life style do all microbial pathogens engage in?
□ A: Photoorganotrophic heterotrophy
□ B: Photolithotrophic autotrophy
□ C: Chemoorganotrophic heterotrophy
□ D: Chemolithotrophic
autotrophy
□ E: Chemophototrophic heteroorganotrophy

Answer 24

□ C: Chemoorganotrophic heterotrophy

Question 25

What life style uses a chemical energy source, an inorganic electron donor, and carbon dioxide as a carbon source?
□ A: Photoorganotrophic heterotrophy
□ B: Photolithotrophic autotrophy
□ C: Chemoorganotrophic heterotrophy
□ D: Chemolithotrophic autotrophy
□ E: Chemophototrophic heteroorganotrophy

Answer 25

□ D: Chemolithotrophic autotrophy

Question 26

In the in vivo induced antigen technology scheme (IVIAT, figure 4-11), what would ideally occur in step 4 when using serum from a tuberculosi processed as outline in the figure?
□ A: Antibodies would not bind and no signal would be generated from any of the phage plaque replicates
□ B: Antibodies would bind to the entire replica filter, generating signal from the entire filter surface, making individual phage plaques indistinguishable
□ C: Antibodies would bind to each phage plaque replicate, generating signal from all of plaques, which would appear as black spots at the positions of th plaques
□ D: Antibodies would only bind to phage plaque replicates that express mycobacterial proteins expressed on the bacterial cell surface within generating signal from just a few spots
□ E: No antibodies of any type would be present for use in step 4

Answer 26

□ D: Antibodies would only bind to phage plaque replicates that express mycobacterial proteins expressed on the bacterial cell surface within generating signal from just a few spots

Question 27

In the microarray scheme (figure 4-12), what would be the signal for a gene that is expressed at a higher level in V. cholerae during growth in th compared to growth during an infection?
□ A: no fluorescent signal since the signals from each labeled DNA sample will cancel each other out
□ B: no fluorescent signal since the procedure only detects fluorescence if genes are expressed at higher levels during infection
□ C: a yellow fluorescent signal (equal levels of Cy3 and Cy5 fluorescence)
□ D: a red fluorescent signal (Cy5 fluorescence greater than Cy3 fluorescence)
□ E: a green fluorescent signal (Cy3 fluorescence greater than Cy5 fluorescence)

Answer 27

□ D: a red fluorescent signal (Cy5 fluorescence greater than Cy3 fluorescence)

Question 28

In signature-tagged mutagenesis (figure 4-8),which of the following is a correct statement about the blank spots in the recovered pool blot?
□ A: the blank spots represent Salmonella mutants that lost the kanamycin resistance gene during growth in the mouse
□ B: the blank spots represent Salmonella mutants that survived in mice
□ C: the blank spots represent Salmonella mutants that lost their DNA sequence tags (variable region) during growth in the mouse
□ D: the blank spots represent Salmonella mutants that did not grow in mice and, therefore, these mutants represent specific genes necessa virulence
□ E: the blank spots represent Salmonella mutants that were not present in the input pool of bacteria

Answer 28

□ D: the blank spots represent Salmonella mutants that did not grow in mice and, therefore, these mutants represent specific genes necessa virulence

Question 29

n the microarray scheme (figure 4-12), what would be the signal for “housekeeping” gene that is expressed at the same level in V. cholerae during an infection and during growth in the laboratory?
□ A: no fluorescent signal since the signals from each labeled DNA sample will cancel each other out
□ E: a green fluorescent signal (Cy3 fluorescence greater than Cy5 fluorescence)
□ B: no fluorescent signal since the microarray does not contain housekeeping gene
□ D: a red fluorescent signal (Cy5 fluorescence greater than Cy3 fluorescence) sequences 1/1
□ C: a yellow fluorescent signal (equal levels of Cy3 and Cy5

Answer 29

□ C: a yellow fluorescent signal (equal levels of Cy3 and Cy5 ????

Question 30

In the in vivo induced antigen technology scheme (IVIAT, figure 4-11), what would occur if step 3 were not performed and the original, unmodified patient serum sample was used for step 4.
□ A: Antibodies would not bind and no signal would be generated from any of the phage plaque replicates
□ B: Antibodies would bind to the entire replica filter, generating signal from the entire filter surface, making individual phage plaques
indistinguishable
□ C: Antibodies would bind to each phage plaque replicate, generating signal from all of plaques, which would appear as black spots at the positions of all the phage plaques
□ D: Antibodies would only bind to phage plaque replicates that express mycobacterial proteins expressed on the bacterial cell surface within the patien generating signal from just a few spots, just as shown in figure 4-11
□ E: No antibodies would be present for use in step 4

Answer 30

□ B: Antibodies would bind to the entire replica filter, generating signal from the entire filter surface, making individual phage plaques
indistinguishable

Question 31

In the in vivo expression technology method to identify virulence genes (IVET, figure 4-9), what is a function of the ampicillin resistance gene on the plasmid?
□ A: to select for Salmonella bacteria that contain the plasmid inserted within their
genome
□ B: to identify candidate virulence genes that are not expressed during laboratory growth
□ C: to identify candidate virulence genes that are transcriptionally active in the mouse
□ D: to prevent growth of E. coli cells containing the pIVET1 plasmid
□ E: to allow growth of Salmonella bacteria within the mouse

Answer 31

□ A: to select for Salmonella bacteria that contain the plasmid inserted within their
genome

Question 32

Which of the following is a correct statement about signature-tagged mutagenesis (figure 4-8)?
□ A: the kanamycin resistance gene is the tag used to compare the input and recovered pools of bacteria
□ B: the kanamycin resistance gene helps the bacteria to survive in mice
□ C: the DNA sequence tags (variable region) are used to compare the input and recovered pools of bacteria
□ D: the dark spots in the recovered pool blot represent bacterial mutants that grew in mice and, therefore, these mutants represent specific genes nece for virulence
□ E: the input pool of bacteria is a mixture of bacterial cells, some of which are kanamycin-resistant and some of which are kanamycin-sensitive

Answer 32

□ C: the DNA sequence tags (variable region) are used to compare the input and recovered pools of bacteria

Question 33

What is the basis of the antibiotic activity of rifampin?
□ A: the drug binds to the 50S subunit and inhibits peptidyltransferase activity
□ B: the drug binds to the 23S rRNA in the 50S subunit, preventing formation of the 70S ini complex
□ C: the drug binds to the 30S subunit and distorts the A site, causing translation misreading
□ D: the drug binds to the 16S rRNA of the 30S subunit, preventing binding of aa-tRNA to A site
□ E: the drug binds to bacterial RNA polymerase, preventing initiation of transcription

Answer 33

□ E: the drug binds to bacterial RNA polymerase, preventing initiation of transcription

Question 34

Which of the following is an correct statement related to the white colonies at step 2 in the Tn-phoA mutagenesis scheme depicted in figure 4-7?
□ A: the PhoA enzyme is expressed outside of the bacterial cells
□ B: the ᵻpho gene is fused to a Vibrio cholera gene that encodes a secreted
protein
□ C: the engineered transposon is not present within cells in the white colonies
□ D: the PhoA enzyme is synthesizing a colored molecule inside bacterial cells
□ E: the pho gene is not fused to a Vibrio cholera gene that encodes a secreted
protein

Answer 34

□ E: the pho gene is not fused to a Vibrio cholera gene that encodes a secreted
protein

Question 35

What is the basis of the antibiotic activity of oxazolidinones?
□ A: the drug binds to the 50S subunit and inhibits peptidyltransferase activity
□ B: the drug binds to the 23S rRNA in the 50S subunit, preventing formation of the 70S ini □ C: the drug binds to the 30S subunit and distorts the A site, causing translation
misreading
□ D: the drug binds to the 16S rRNA of the 30S subunit, preventing binding of aa-tRNA to A site
□ E: the drug binds to bacterial RNA polymerase, preventing initiation of transcription

Answer 35

□ B: the drug binds to the 23S rRNA in the 50S subunit, preventing formation of the 70S ini

Question 36

Which antibiotic binds the terminal D-Ala-D-Ala of peptide side chains of peptidoglycan subunits, sterically
inhibiting addition of new subunits to the cell wall?
□ A: chloramphenicol
□ B: cycloserine
□ C: vancomycin
□ D: tetracycline □ E: bacitracin

Answer 36

□ C: vancomycin

Question 37

How does ciprofloxacin act as an antibiotic?
□ A: binds a human topoisomerase and prevents it from being used by bacteria
□ B: binds some types of double strand breaks in bacterial DNA and prevents their repair
□ C: binds some types of double strand breaks in human DNA and prevents their repair
□ D: binds bacterial RNA and prevents translation
□ E: binds the bacterial 50S ribosomal subunit and prevents the peptidyltransferase reaction

Answer 37

□ B: binds some types of double strand breaks in bacterial DNA and prevents their repair

Question 38

Which of the following antibiotic inhibits folic acid synthesis?
□ A: Dapsone
□ B: Isoniazid
□ C: Ethambutol 
□ D: Cycloserine 
□ E: Trimethoprim

Answer 38

□ A: Dapsone

Question 39

Which is true about the antibacterial compound tazobactam?
□ A: it is a beta-lactam compound
□ B: it blocks the joining of peptidoglycan subunits to the peptidoglycan network
□ C: it is a beta lactamase
□ D: it is cephalosporin
□ E: it is a beta-lactamase inhibitor

Answer 39

□ E: it is a beta-lactamase inhibitor

Question 40

A potential antibiotic is found to have a ratio of 0.01 for the toxic dose relative to the therapeutic dose. Which of
the following is true?
□ A: the therapeutic index is 1000
□ B: the therapeutic index is 0.01
□ C: the drug is definitely not safe for use in patients
□ D: the therapeutic index suggests the drug is safe and effective □ E: the drug has a zone of inhibition of 100mm

Answer 40

□ B: the therapeutic index is 0.01

Question 41

What is an example of an endgenously acquired disease?

Answer 41

A: pneumonia

Question 42

What class of nutrient uptake system in bacteria uses permeases
to move substances from higher to lower concentration, without
energy input?

Answer 42

A: facilitated diffusion

Question 43

What is the role of MHC molecules in the recognition of infected
cells by NK cells, and what is the physiological recognition?

Answer 43

A: MHC molecules are expressed by “self cells”, bind to the inhibitor
recpeotr on NK and tell the NK to not kill these cells. If this molecule is
missing then the inhibitor receptor is not activated and NK know that it is a foreign cell and lysis is induced.

Question 44

What are 3 classes of innate immunity receptors and give an
example of a microbial substance recognized by each class of
receptor.

Answer 44

?
A: Toll-like receptors - extracellular PAMPs (ex: bacterial flagella) Nod-like receptors - intracellular DAMPs or PAMPS (parts of ingested microbes) rig-like receptors - intracellular viruses (pieces of ingested viruses)

TOLL: PAMPs
RIG: viral RNA
NOD: PAMPs and DAMPs

Question 45

How does the specificity of innate immunity differ from that of adaptive immunity?

Answer 45

A: adaptive is highly specific,

whereas innate is not

Question 46

What are the 2 types of adaptive immunity and what types of microbes do these adaptive immune responses combat?

Answer 46

A: humoral and cell-mediated immunity. humoral combats extracellular microbes and cell-mediated combats phagocytosed microbes and virus-infected cells.

Question 47

Where are T and B lymphocytes located in lymph nodes and how is anatomical separation accomplished? (2 points)

Answer 47

A: T lymphocytes are located in the parafollicular cortex of the lymph node and b cells are located in the follicle. The anatomical separation is maintained through expression of cytokines specific to b and t cells in the areas that they are restricted to.

Question 48

What are the 4 principal classes of lymphocytes and list an effector function for each class.

Answer 48

A: B lymphocytes - humoral immunity through antibody production
Helper T lymphocytes - recognize dendritic APC’s and release cytokines to induce immune response
Cytotoxic T lymphocytes - release enzymes within an infected cell to induce lysis
Regulatory T lymphocytes - protect our self cells by suppressing our own immune response to them

Question 49

What is a common mechanism of bacterial resistance to
quinolones? (1 point) Name another specific mechanism of
bacterial antibiotic resistance of your choice. (1 point)

Answer 49

A: bacteria will mutate their DNA gyrase or their topoisomerases to resist quinolones. bacteria will use an efflux pump to resist tetracyclines.

Question 50

What is the mechanism of action of the antibiotic chloramphenicol?

Answer 50

A: binds the 50S subunit of the ribosome and prevents the

peptidyltransferase reaction from occurring

Question 51

What is the mechanism of action of the antibiotic penicillin? (1 point)

Answer 51

A: mimics the d-ala d-ala linkage and inhibits transpeptidation of the Peptidoglycan structure

Question 52

Name the 3 ways that antibiotic resistance genes can be transferred at high frequency from one bacterium to
another? (3 points)

Answer 52

A: conjugation, transduction, and transposition

Question 53

Describe the key components of Augmentin in treating a bacterial infection. (2 points)

Answer 53

A: Augmentin is a mixture of amoxicillin and clavulanic acid. This is a mixture of a B-lactam penicillin that will mimic the d-ala d-ala
bond and inhibit transpeptidation, with a b-lactamase inhibitor that overcomes the bacterial resistance mechanism of b-lactamase.

Question 54

In testing antibiotic A by the disk diffusion assay, bacterium X has an inhibition zone of 14 mm. See the chart
relating inhibition zone and antibiotic concentration. The drug safely achieves a concentration of 16-32 micrograms per milliliter in the human body. What conclusion can you make about the effectiveness of the antibiotic in a patient? (1 point)

Answer 54

A: This drug is right on the border of being resistant, to being ineffective. So overall this drug will not be effective in treating bacterium X.

Question 55

What are 3 factors that influence the ability of an antibiotic to reach its minimal inhibitory concentration in a
patient? (3 points)

Answer 55

A: The amount of the drug that is given, its rate of clearance from the body, and its rate of uptake into the bacteria or cell

Question 56

Define the therapeutic index for an antibiotic? (1 point)

Answer 56

A: the ratio of the toxic dose to the therapeutic dose of an antibiotic

Question 57

In the in vivo expression technology method to identify virulence genes (IVET, figure 4-9), what is a function of the purA gene on the plasmid? (1 point)

Answer 57

To look for genes of S. typhimurium that are expressed during infection
?

NOT
A: Having the PurA gene on the plasmid will allow the bacteria to to be virulent in vivo and show you whether or not salmonella growth was able to occur in the spleen of the mouse.

Question 58

In the microarray scheme (figure 4-12), what would be the fluorescence characteristic of the signal for a gene that is expressed at a higher level in V. cholerae during growth in the laboratory compared to growth during an infection? (1 point)

Answer 58

A: Cy5-labeled and red fluorescence

Question 59

With respect to the goals of the experimental plan, what are the most important properties of a transposon
insertion in bacteria in a dark colony at step 2 in the Tn-phoA mutagenesis scheme depicted in figure 4-7? (2 points)

Answer 59

ORF promoter upstream of ‘phoA
?

NOT
A: The dark colonies are PhoA+, are producing alkaline phosphatase, and therefore we know that they possess our transposon 20

Question 60

With respect to the goals of the experimental plan, what is the important property of the cells growing on the petri
dish in step 7 of the scheme depicted in figure 4-3? (1 point)

Answer 60

A: These cells are E. coli that were able to invade mammalian cells and therefore have acquired the invasin gene

Question 61

What is gentamicin used for in step 5 of the scheme depicted in figure 4-3? (1 point)

Answer 61

A: washes away any E. Coli that did not invade the mammalian cells, therefore washes away the E. coli that did not receive the invasin gene

Question 62

In the in vivo induced antigen technology scheme (IVIAT, figure 4-11), what happens in step 4 when using serum
from a tuberculosis patient that has been processed as outline in the figure? (1 point)

Answer 62

?

NOT
A: in step 4, we see dark spots in those spots where the Tb antibody was present

Question 63

In signature-tagged mutagenesis (figure 4-8) (1) what do the blank areas in the recovered pool blot represent and (2) are they of interest or not of interest for further study to the researchers and (3) why? (3 points)

Answer 63

A: Blank spots show spots in the genome where virulence was knocked out and we see anti-virulence. They are of interest because it can tell you that that transposon “hopped” into the spot of a virulence factor and possibly where in the genome virulence factors are located.

Question 64

In step 4 of figure 4-10, why are bacterial cells run through the fluorescence activated cell sorter? (1 point)

Answer 64

A: this shows whether or not they fluoresce in vitro (which we only are looking for fluorescence in vivo)

Question 65

A cell has abundant levels of tryptophan and, as a consequence, decreases the production of an enzyme for tryptophan biosynthesis by preventing initiation of transcription of the mRNA for the enzyme. What is the role of
tryptophan in this type of regulation, as discussed in class? (1 point)

Answer 65

A: Tryptophan acts as a corepressor to activate the repressor in this situation

Question 66

What is the main phosphorus source for bacteria? (1 point)

Answer 66

A: inorganic phosphate

Question 67

Name a nutrient brought into a bacterial cell by group translocation and describe a key feature of this mode of
import. (2 points)

Answer 67

A: Glucose is brought into the cell by group translocation, in which it is modified to be glucose-6-phosphate.

Question 68

28 Name an oral bacterial genus whose members are strict anaerobes? (1 point)

Answer 68

A: Prevotella

Question 69

Regarding organism lifestyles, as discussed in class, what 3 lifestyle features are described by the term
chemoorganotrophic heterotrophy? (3 points)

Answer 69

A: organic or inorganic energy source organic electron donor organic carbon source

Question 70

A cell has abundant levels of tryptophan and, as a consequence, decreases the activity of an enzyme for tryptophan biosynthesis through the binding of tryptophan itself to a site on the enzyme that is not the active site.
(1) What class of enzyme is subject to such feedback regulation and (2) what is one possible way the binding of tryptophan to the enzyme can result in a change in enzymatic activity? (2 points)

Answer 70

A: This is an example of allosteric regulation. One way that tryptophan binding to the enzyme can change enzymatic activity by changing the vmax of the reaction to slow the production of enzymes for tryptophan biosynthesis.

Question 71

31 Name the 3 structural components of a peptidoglycan subunit. (3 points)

Answer 71

NAG, NAM, crosslinked peptide chains
?

2/3
A: NAG, NAM, phosphate bond

Question 72

What component of bacterial cells is the most significant in conferring cell shape (rod, spiral, etc.)? (1 point)

Answer 72

A: Cell wall

Question 73

Name 3 properties of saliva, as discussed in class. (3 points)

Answer 73

A: promotes bacterial aggregation, maintains pH, promotes pellicle formation on tooth surfaces

Question 74

Name 3 properties of bacterial LPS, as presented in class. (no credit for stating something to the effect that it is
bacterial – I need more detail) (3 points)

Answer 74

A: bacterial LPS have an o antigen, a core polysaccharide, and a lipid A portion.

Question 75

What are 3 nutritional macroelements required for building cell components? (3 points)

Answer 75

A: Carbon, oxygen, nitrogen

Question 76

36 Which fluid of the oral cavity has a composition similar to serum within the blood stream? (1 point)

Answer 76

A: Gingival crevicular fluid

Question 77

What is the approximate quantity of bacteria of a typical human microbiome (percentage of a person’s weight composed of bacteria OR the number of bacterial cells relative to the number of the person’s cells)?

Answer 77

A: there are 10X more bacteria than human cells

Question 78

What are the long, thick, proteinaceous appendages produced on a bacterial cell’s surface numbering only 1-
10/cell, through which DNA can be transferred to another bacterium? (1 point)

Answer 78

A: sex pili

Question 79

39 What specific type of cells have teichoic acid as a cell wall component? (1 point)

Answer 79

A: gram + bacteria

Question 80

What cells have teichoic acid as a cell wall component?

X A: gram-negative bacteria
X B: gram-positive bacteria
X C: human cells
X D: some eukaryotic microbes X E: all spore-forming bacteria

Answer 80

> B: gram-positive bacteria

Question 81

Which of the following molecules densely project from the surfaces of most gram negative bacteria?

X A: teichoic acids
X B: siderophores
X C: lipopolysaccharides 
X D: hopanoids
X E: Braun's lipoproteins

Answer 81

> C: lipopolysaccharides

Question 82

What is a not property associated with the normal bacterial flora of a human body?

X A: detoxification of carcinogens
X B: occupies space to crowd out disease-causing microbes
X C: produces some vitamins that we do not have the genes to make
X D: begins to accumulate in utero
X E: teaches our immune systems how to recognize dangerous invaders

Answer 82

X D: begins to accumulate in utero

Question 83

Which is true of peptidoglycan?

X A: the peptide component is translated by the ribosome
X B: the peptide component of peptidoglycan is linked to N-acetylglucosamine
X C: it is polysaccharide layer that promotes movement of gliding bacteria
X D: it forms a thin layer in gram negative bacteria compared to gram positive bacteria
X E: it is a precursor to teichoic acid

Answer 83

X D: it forms a thin layer in gram negative bacteria compared to gram positive bacteria

Question 84

Which is a property of saliva?

X A: composition is similar to serum within the blood stream X B: flushes bacteria out of gingival crevice
X C: promotes aggregation of bacteria
X D: responsible for pH changes in oral cavity
X E: contains high numbers of neutrophils

Answer 84

X C: promotes aggregation of bacteria

Question 85

Where in the oral cavity would you expect to find the largest numbers of neutrophils?

X A: saliva
X B: dorsum of tongue
X C: buccal mucosa
X D: gingival crevicular fluid
X E: where dental appliances contact teeth

Answer 85

X D: gingival crevicular fluid

Question 86

Fimbriae

X A: are numerous (up to 1000/cell) short, thin, hairlike, proteinaceous appendages on a bacterial cells surface
X B: are long, thick, proteinaceous appendages on a bacterial cells surface numbering only 1-10/cell
X C: are networks of polysaccharides that coat bacterial cells
X D: provide bacteria protection from osmotic stress
X E: are composed of substructures called a filament, a basal body, and a hook

Answer 86

X A: are numerous (up to 1000/cell) short, thin, hairlike, proteinaceous appendages on a bacterial cells surface

Question 87

What is the most likely example of an exogenously acquired disease?

X A: HIV/AIDS acquired in utero
X B: common cold from a rhinovirus infection
X C: staphylococcal infection from a cut in the skin
X D: pneumonia from microaspirations of Pneumococcus bacteria X E: uninary tract infection by E. coli

Answer 87

> B: common cold from a rhinovirus infection

Question 88

Allosteric regulation can directly result in

X A: termination of transcription
X B: binding of a repressor protein to an operator site
X C: an increase in transcription
X D: change in the Vmax of an enzyme
X E: removal of a repressor protein to an operator site

Answer 88

X D: change in the Vmax of an enzyme

Question 89

Which of the following is not an example of a nutritional macroelement required for building cell components?

X A: oxygen
X B: hydrogen 
X C: phophorus 
X D: sulphur
X E: zinc

Answer 89

X E: zinc

Question 90

Which is a typical sulfur source for bacterial cells?

X  A: sulfate
X B: sulfur dioxide
X C: hydrogen sulfide 
X D: sulfanilamide
X E: methionine

Answer 90

X A: sulfate

Question 91

Which is an example of a bacterial genus whose members are so limited in their ability to exploit environmentally available compounds as carbon and energy sources that they have adopted an obligate intracellular lifestyle?

X A: Chlamydia
X B: Pseudomonas 
X C: Staphylococcus 
X D: Streptococcus 
X E: Escherichia

Answer 91

X A: Chlamydia

Question 92

What life style do all microbial pathogens engage in?

X A: Photoorganotrophic heterotrophy 
X B: Photolithotrophic autotrophy
X C: Chemoorganotrophic heterotrophy 
X D: Chemolithotrophic autotrophy
X E: Chemophototrophic heteroorganotrophy

Answer 92

> C: Chemoorganotrophic heterotrophy

Question 93

A cell has abundant levels of tryptophan and, as a consequence, stops transcription of genes for tryptophan biosynthesis through the binding of a protein to the operator site adjacent to these genes. This is an example of

X A: attenuation
X B: allosteric regulation
X C: gene repression by a corepressor 
X D: gene induction by an inducer
X E: group translocation

Answer 93

X C: gene repression by a corepressor

Question 94

Import of glucose into bacterial cells

X A: uses a permease to facilitate movement of glucose across the plasma membrane
X B: involves chemical alteration of glucose as part of the transport process
X C: only occurs if the glucose can move passively down a concentration gradient
X D: uses a proton gradient in the import process
X E: requires a siderophore

Answer 94

X B: involves chemical alteration of glucose as part of the transport process

Question 95

A cell is exposed to lactose and, as a consequence, increases the production of enzymes for lactose utilization by increasing initiation of transcription of the mRNA for the enzymes. This is an example of

X A: attenuation
X B: allosteric regulation
X C: gene repression by a corepressor 
X D: gene induction by an inducer
X E: group translocation

Answer 95

X D: gene induction by an inducer

Question 96

What is gentamicin used for in step 5 of the scheme depicted in figure 4-3?

X A: to kill E. coli cells that are present outside of mammalian cells
X B: to select for E. coli cells that contain a suicide plasmid
X C: to liberate E. coli cells that are present inside of mammalian cells
X D: to select for E. coli cells that contain a transposon insertion
X E: to promote the invasion of mammalian cells by E. coli

Answer 96

X A: to kill E. coli cells that are present outside of mammalian cells

Question 97

In signature-tagged mutagenesis (figure 4-8),which of the following is a correct statement about the blank spots in the recovered pool blot?

X A: the blank spots represent Salmonella mutants that lost the kanamycin resistance gene during growth in the mouse
X B: the blank spots represent Salmonella mutants that survived in mice
X C: the blank spots represent Salmonella mutants that lost their DNA sequence tags (variable region) during growth in the mouse
X D: the blank spots represent Salmonella mutants that did not grow in mice and, therefore, these mutants represent specific genes necessary for virulence
X E: the blank spots represent Salmonella mutants that were not present in the input pool of bacteria

Answer 97

X D: the blank spots represent Salmonella mutants that did not grow in mice and, therefore, these mutants represent specific genes necessary for virulence

Question 98

In step 5 of figure 4-10, why are bacterial cells reintroduced into macrophages and run through the fluorescence activated cell sorter?

X A: to retest bacterial cells that fluoresced on their own because these are the bacteria of interest
X B: to identify bacterial cells that fluoresce within macrophages from the bacterial cell population that also fluoresced when growing on their own in a lab environment, since these are the bacteria of interest
X C: to create a pure population of bacteria that do not fluoresce when within macrophages, since these are the bacteria of interest
X D: to identify bacterial cells that fluoresce within macrophages from the bacterial cell population that did not fluoresce when growing on their own in a lab environment, since these are the bacteria of interest
X E: the researchers are seeking any bacterial gene fusion that expresses green fluorescent protein (gfp), whether in the lab environment or within macrophages

Answer 98

X D: to identify bacterial cells that fluoresce within macrophages from the bacterial cell population that did not fluoresce when growing on their own in a lab environment, since these are the bacteria of interest

Question 99

In the in vivo expression technology method to identify virulence genes (IVET, figure 4-9), what is a function of the ampicillin resistance gene on the plasmid?

X A: to select for Salmonella bacteria that contain the plasmid inserted within their genome
X B: to identify candidate virulence genes that are not expressed during laboratory growth
X C: to identify candidate virulence genes that are transcriptionally active in the mouse
X D: to prevent growth of E. coli cells containing the pIVET1 plasmid
X E: to allow growth of Salmonella bacteria within the mouse

Answer 99

X A: to select for Salmonella bacteria that contain the plasmid inserted within their genome

Question 100

In the microarray scheme (figure 4-12), what would be the signal for a housekeeping gene that is expressed at the same level in V. cholerae during an infection and during growth in the laboratory?

X A: no fluorescent signal since the signals from each labeled DNA sample will cancel each other out
X B: no fluorescent signal since the microarray does not contain housekeeping gene sequences
X C: a yellow fluorescent signal (equal levels of Cy3 and Cy5 fluorescence)
X D: a red fluorescent signal (Cy5 fluorescence greater than Cy3 fluorescence)
X E: a green fluorescent signal (Cy3 fluorescence greater than Cy5 fluorescence)

Answer 100

X C: a yellow fluorescent signal (equal levels of Cy3 and Cy5 fluorescence)

Question 101

Which of the following is an correct statement related to the white colonies at step 2 in the Tn-phoA mutagenesis scheme depicted in figure 4-7?

X A: the PhoA enzyme is expressed outside of the bacterial cells
X B: the pho gene is fused to a Vibrio cholera gene that encodes a secreted protein
X C: the engineered transposon is not present within cells in the white colonies
X D: the PhoA enzyme is synthesizing a colored molecule inside bacterial cells
X E: the pho gene is not fused to a Vibrio cholera gene that encodes a secreted protein

Answer 101

X E: the pho gene is not fused to a Vibrio cholera gene that encodes a secreted protein

Question 102

Which of the following is true about the RNA sequencing (RNA-seq) method for identifying bacterial virulence
factors?

X A: RNA-seq is less sensitive than microarray analysis
X B: RNA-seq can be performed on impure samples that contain multiple bacterial species as well as host cells
X C: RNA-seq was used to identify genomic regions that are unique to pathogenic E. coli O157:H7 and not present in non- pathogenic strains
X D: RNA-seq does not depend on knowing the genome sequence of the pathogen of interest

Answer 102

X B: RNA-seq can be performed on impure samples that contain multiple bacterial species as well as host cells

Question 103

In the in vivo induced antigen technology scheme (IVIAT, figure 4-11), what would occur if step 3 were not performed and the original, unmodified patient serum sample was used for step 4.

X A: Antibodies would not bind and no signal would be generated from any of the phage plaque replicates
X B: Antibodies would bind to the entire replica filter, generating signal from the entire filter surface, making individual phage plaques indistinguishable
X C: Antibodies would bind to each phage plaque replicate, generating signal from all of plaques, which would appear as black spots at the positions of the all the phage plaques
X D: Antibodies would only bind to phage plaque replicates that express mycobacterial proteins expressed on the bacterial cell surface within the patient, generating signal from just a few spots, just as shown in figure 4-11
X E: No antibodies would be present for use in step 4

Answer 103

X B: Antibodies would bind to the entire replica filter, generating signal from the entire filter surface, making individual phage plaques indistinguishable

Question 104

For a useful antibiotic, the therapeutic index

X A: must be greater than 1000
X B: is equal to 1
X C: must be less than 1
X D: can be greater than 1, equal to 1, or less than 1 depending on the antibiotic
X E: must be significantly greater than 1 but can be as low as 2 for some drugs

Answer 104

X E: must be significantly greater than 1 but can be as low as 2 for some drugs

Question 105

What is meant by the therapeutic index for an antibiotic?

X A: minimal inhibitory concentration (MIC)
X B: minimal bacteriocidal concentration (MBC)
X C: the ratio of the toxic dose to the therapeutic dose
X D: the ratio of the therapeutic dose to the toxic dose
X E: the ratio of the zone of inhibition to the drug concentration in the body

Answer 105

X C: the ratio of the toxic dose to the therapeutic dose

Question 106

In testing antibiotic A by the disk diffusion assay, bacterium X has an inhibition zone of 14 mm. See the chart relating inhibition zone and antibiotic concentration. The drug safely achieves a concentration of 8-16 micrograms per milliliter in the human body. Which of the following is true?

X A: The antibiotic will be effective against bacterium X in a patient
X B: The antibiotic will be ineffective against bacterium X in a patient
X C: It is not possible to tell from the above information if the antibiotic will be effective or not in a patient
X D: The antibiotic will be effective at all concentrations <16 micrograms per milliliter in a patient
X E: The antibiotic will be effective at all concentrations >8 micrograms per milliliter in a patient

Answer 106

X B: The antibiotic will be ineffective against bacterium X in a patient

Question 107

What unique mechanism for transferring antibiotic resistance genes could occur at relatively high frequency for a gene on a bacterial chromosome adjacent to a phage genome insertion site?
X A: conjugation
X B: transduction
X C: transposition
X D: integrin transfer X E: transformation

Answer 107

X B: transduction

Question 108

What is a common mechanism of bacterial resistance to tetracyclines?
29
X A: hydrolysis of -lactam ring by -lactamase
X B: drug-resistant dihydrofolate reductase
X C: drug-resistant dihydropteroate synthase
X D: methylation of 23S rRNA
X E: activation/acquisition of a drug efflux pump

Answer 108

X E: activation/acquisition of a drug efflux pump

Question 109

Which of the following compounds are not beta-lactam antibiotics?

X A: carbapenems 
X B: penicillins
X C: tetracyclines
X D: cephalosporins 
X E: monobactams

Answer 109

X C: tetracyclines

Question 110

How does ciprofloxacin act as an antibiotic?

X A: binds a human topoisomerase and prevents it from being used by bacteria
X B: binds some types of double strand breaks in bacterial DNA and prevents their repair
X C: binds some types of double strand breaks in human DNA and prevents their repair
X D: binds bacterial RNA and prevents translation
X E: binds the bacterial 50S ribosomal subunit and prevents the peptidyltransferase reaction

Answer 110

X B: binds some types of double strand breaks in bacterial DNA and prevents their repair

Question 111

What is one key strategy for preventing the emergence of antibiotic resistance in pathogenic bacteria?

X A: administering antibiotics in minimal amounts (use low concentrations)
X B: using antibiotics freely, even when uncertain that an illness is caused by bacteria
X C: annual vaccination programs for seasonal illnesses
X D: limiting contact with animal sources of infectious diseases
X E: giving 2 or more antibiotics at the same time

Answer 111

X E: giving 2 or more antibiotics at the same time

Question 112

In addition to T cells, which cell type is required for initiation of all T cellmediated immune responses?

X A: Effector cells
X B: Memory cells
X C: Natural killer cells
X D: Antigen-presenting cells 
X E: B lymphocytes

Answer 112

X D: Antigen-presenting cells

Question 113

The principal function of the immune system is:

X A: Defense against cancer
X B: Repair of injured tissues
X C: Defense against microbial infections
X D: Prevention of inflammatory diseases
X E: Protection against environmental toxins

Answer 113

X C: Defense against microbial infections

Question 114

The two major functional classes of effector T lymphocytes are:

X A: Helper T lymphocytes and cytotoxic T lymphocytes
X B: Natural killer cells and cytotoxic T lymphocytes
X C: Memory T cells and effector T cells
X D: Helper cells and antigen-presenting cells
X E: Cytotoxic T lymphocytes and target cells

Answer 114

X A: Helper T lymphocytes and cytotoxic T lymphocytes

Question 115

A previously healthy 8-year-old boy is infected with an upper respiratory tract virus for the first time. During the first few hours of infection, which one of the following events occurs?

X A: The adaptive immune system responds rapidly to the virus and keeps the viral infection under control.
X B: The innate immune system responds rapidly to the viral infection and keeps the viral infection under control.
X C: Passive immunity mediated by maternal antibodies limits the spread of infection.
X D: B and T lymphocytes recognize the virus and stimulate the innate immune response.
X E: The virus causes malignant transformation of respiratory mucosal epithelial cells, and the malignant cells are recognized by the adaptive immune system.

Answer 115

X B: The innate immune system responds rapidly to the viral infection and keeps the viral infection under control.

Question 116

A standard treatment of animal bite victims, when there is a possibility that the animal was infected with the
37 rabies virus, is administration of human immunoglobulin preparations containing antirabies virus antibodies.
Which type of immunity would be established by this treatment?

X A: Active humoral immunity
X B: Passive humoral immunity
X C: Active cell-mediated immunity 
X D: Passive cell-mediated immunity 
X E: Innate immunity

Answer 116

X B: Passive humoral immunity

Question 117

Antibodies and T lymphocytes are the respective mediators of which two types of immunity?

X A: Innate and adaptive
X B: Passive and active
X C: Specific and nonspecific
X D: Humoral and cell-mediated 
X E: Adult and neonatal

Answer 117

X D: Humoral and cell-mediated

Question 118

At 15 months of age, a child received a measles-mumps-rubella vaccine (MMR). At age 22, she is living with a
39 family that has not been vaccinated and she is exposed to measles. Despite the exposure, she does not become
infected. Which of the following properties of the adaptive immune system is best illustrated by this scenario?

X A: Specificity
X B: Diversity
X C: Specialization
X D: Memory
X E: Nonreactivity to self

Answer 118

X D: Memory

Question 119

Which of the following cell types is required for all humoral immune responses?

X A: Natural killer cells
X B: Dendritic cells
X C: Cytolytic T lymphocytes 
X D: B lymphocytes
X E: Helper T lymphocytes

Answer 119

X D: B lymphocytes

Question 120

Which of the following is a unique property of the adaptive immune system?

X A: Highly diverse repertoire of specificities for antigens
X B: Self-nonself discrimination
X C: Recognition of common microbial structures
X D: Protection against viral infections
X E: Responses that have the same kinetics and magnitude on repeated exposure to the same microbe

Answer 120

X A: Highly diverse repertoire of specificities for antigens

Question 121

A 4-year-old girl stepped on a rusty nail in her backyard. Two days later, she is taken to the pediatrician because her heel is painful, red, and swollen and is warm to the touch. All of the following are mechanisms of innate immunity that may be protecting the patient against pathogenic microbes in the heel wound EXCEPT:
X A: Intraepithelial lymphocytes present in the skin
X B: Circulating neutrophils migrating to the site of the wound
X C: Soluble cytokines that induce a local inflammatory response
X D: Circulating anti-tetanus toxin antibodies

Answer 121

X D: Circulating anti-tetanus toxin antibodies

Question 122

Which of the following comparisons of the innate and adaptive immune systems is FALSE?

X A: The innate immune system is more likely to recognize normal self, and therefore cause autoimmunity, than is the adaptive immune system.
X B: Receptors used for recognition in innate immunity are encoded in the germline, whereas those of the adaptive immune system are encoded by genes generated via somatic recombination of germline receptor gene loci.
X C: The innate and adaptive immune systems share some of the same effector mechanisms.
X D: Both the innate and adaptive immune systems can recognize nonmicrobial substances.
X E: The innate immune system does not have memory but the adaptive immune system does

Answer 122

X A: The innate immune system is more likely to recognize normal self, and therefore cause autoimmunity, than is the adaptive immune system.

Question 123

Which of the following is a Toll-like receptor ligand?

X A: peptidoglycan
X B: transfer RNA (tRNA) 
X C: IL-2
X D: cytosolic DNA
X E: cytosolic RNA

Answer 123

X A: peptidoglycan

Question 124

What is NOT a possible eventual response to activation of signaling through Toll-like receptors (TLRs)?

X A: inflammation
X B: stimulation of adaptive immunity 
X C: antiviral state
X D: tolerance to TLR ligand
X E: macrophage activation

Answer 124

X D: tolerance to TLR ligand