Bacteriology 303

University of Wisconsin-Madison

Sample Questions from Previous Examinations

This is not a sample exam or a practice exam. These are some sample questions from previous exams. The answers are not available online because that would disallow the use of these questions as a study tool. Please refer to your notes and readings for solutions to questions or tips on how to solve the problems. For each of these questions there is one correct answer.

1. The phylogenetic tree of the living world is derived from sequencing of
A. chromosomal DNA
B. 16S or 18S ribosomal RNA
C. transfer RNA
D. ribosomal proteins
E. none of the above 


2. Which of the following cellular features is found in Archaea, but not in Eukarya or Bacteria?
A. procaryotic cellular organization
B. 70S ribosomes
C. cell walls consisting of murein
D. membranes consisting of ether-linked isoprenoids
E. transcription and translation are coupled 


3. Which of the following is a characteristic of protein synthesis in both Archaea and Eukarya?
A. Transcription and translation are coupled.
B. The initiator tRNA is methionine.
C. The initiator tRNA is N-formyl-methionine.
D. Protein synthesis is inhibited by tetracycline.
E. None of the above 


4. A metabolic characteristic found in the Bacteria that never occurs in Archaea or Eukarya is
A. anoxygenic photosynthesis
B. oxygenic photosynthesis
C. lithotrophy
D. halophily
E. thermophily 


5. The approximate size of a typical bacterial cell (e.g. E. coli or Staphylococcus) is
A. 100 nanometers
B. 1 micrometer
C. 10 micrometers
D. 10-3 centimeters
E. 0.01 millimeters 


6. The macromolecule that makes up the highest percentage of the dry weight of bacterial cells is
A. DNA
B. lipopolysaccharide
C. peptidoglycan
D. protein
E. RNA 


7. The genetic and biochemical similarities between existing cyanobacteria and eukaryotic chloroplasts is evidence that
A. Archaea evolved into eukaryotes
B. photosynthesis first evolved in an anaerobic environment
C. oxygenic photosynthesis first evolved in eukaryotes
D. chloroplasts and cyanobacteria share a common evolutionary ancestor
E. cyanobacteria arose from chloroplasts which escaped from plant cells 


Questions 8 -11 refer to the following diagram of the muropeptide subunit of the cell wall peptidoglycan of E. coli.



8. The peptide bond attaching N-acetylmuramic acid to L-alanine is shown by pointer
A. I
B. II
C. III
D. IV
E. none of the above 

9. The pointer to the bond whose formation is inhibited by beta-lactam antibiotics is
A. II
B. III
C. V
D. VI
E. none of the above 


10. The arrow pointing to the bond that is cleaved by lysozyme is
A. II
B. III
C. IV
D. V
E. none of the above 


11. Which component of this peptidoglycan is a diamino dicarboxylic acid ?
A. D-glutamate
B. D-glutamine
C. L-lysine
D. L-glycine
E. Diaminopimelic acid 


12. The function of peptidoglycan in the cell wall of the E.coli is to
A. serve as a permeability barrier to all solutes except H2O
B. prevent osmotic lysis of the cell protoplast
C. regulate the passage of solutes through the cell wall
D. regulate the passage of solutes into and out of the cell
E. none of the above 


13. The interpeptide bridge of Gram-positive bacterial murein (e.g. the pentaglycine bridge in Staphylococcus aureus) connects
A. Diaminopimelic acid to D-alanine
B. L-lysine to D-alanine
C. L-lysine to D-glutamate
D. Diaminopimelic acid to l-lysine
E. D-lysine to L-lysine 


Questions 14-17 refer to the following schematic drawing of the ultrastructure of the flagellum of E. coli (after Adler).



14. What is the unit of measurement of the flagellar dimensions?
A. angstroms
B. nanometers
C. micrometers
D. millimeters
E. centimeters 

15. The flagellar motor (M) ring is indicated by pointer
A. F
B. B
C. C
D. D
E. E 


16. Which component of the flagellar apparatus did Pate find to be absent in the gliding bacterium, Cytophaga?
A. A
B. B
C. C
D. D
E. E and F 


17. Which part of the flagellar apparatus is absent in the spirochetes and in Gram-positive bacteria?
A. A
B. B
C. C and D
D. E and F
E. none of the above 


18. Most of the spiral-shaped and curved bacteria are motile by means of polar flagella. From this information what would you predict is their most likely habitat?
A. water
B. soil
C. marine sediments
D. skin of animals
E. intestinal tracts of animals 


19. The endoflagella (axial filaments) of spirochetes are also referred to as periplasmic flagella because
A. they reside between the inner membrane and an outer membrane of the cell
B. they contain the entire flagellar apparatus except the filament, and hence, can only be used for gliding motility
C. they are located uniformly on the surface of the cell
D. although the cells are motile, these structures are not involved in the characteristic type of swimming movement of spirochetes
E. they are cellular appendages continuous with the plasma membrane and cell wall 


20. The function of the sex (F) pilus of Escherichia coli involves
A. transport of nutrients
B. attachment of cells to inert surfaces
C. movement of cells in a type of twitching motion
D. transfer of DNA between bacteria during conjugation
E. organization and folding of the bacterial chromosome within the cytoplasm 


21. The capsule of procaryotic cells, including slime layers and glycocalyx, may be used to
A. digest nutrients on the surfaces of cells
B. attach mating cells during the process of conjugation
C. attach cells to solid surface and initiate formation of a biofilm
D. provide buoyancy for cells in aquatic habitats
E. regulate the passage of solutes into and out of the cell 


Questions 22 -26 refers to the drawing below of the ultra structure of the cell surface of Escherichia coli.


22. The structure shown by pointer III is
A. omp C or omp F porin
B. omp A protein
C. Braun lipoprotein
D. Lipid A
E. flagellar L-ring 


23. The function of this structure (pointer III above) is
A. active transport of solutes across the plasma membrane
B. support of the bacterial flagellum
C. maintain the lateral stability of the outer membrane
D. anchor the outer membrane to the underlying peptidoglycan sheet
E. allow passage of solutes through the outer membrane 


24. Bracket B defines the limits of the
A. outer membrane
B. plasma membrane
C. cytoplasm
D. periplasm
E. capsule 


25. Which component is lipopolysaccharide?
A. I
B. II
C. V
D. D
E. E 


26. Which component is peptidoglycan?
A. A
B. IV
C. C
D. D
E. E 


27. Gram-negative bacteria are typically less susceptible to penecillin than are Gram-positive bacteria because
A. they lack a transport system for penicillin
B. they degrade penicillin in the periplasmic space by means of penicillinase enzymes
C. they lack peptidoglycan in their cell wall
D. their peptidoglycan is chemically modified to be resistant to attack by penicillin
E. their outer membrane is an effective permeability barrier 


28. Polybetahydroxybutyric acid and glycogen are formed by bacterial cells as
A. reserves of carbon and energy
B. reserves of nitrogen
C. waste material
D. molecular ligands to attach bacterial cells to surface receptors
E. none of the above 


29. A procaryote possessing carboxysomes and chlorosomes as inclusions in its cytoplasm probably has this type of metabolism.
A. photoautotrophic
B. photoheterotrophic
C. lithoautotrophic
D. heterotrophic
E. fermentative 


30. This is the common inclusion observed in purple and green bacteria and lithotrophs such as Thiobacillus.
A. sulfur
B. polyphosphate
C. parasporal crystals
D. PHB granules
E. magnetosomes 


31. Compared to the vegetative cells that form them, bacterial endospores have
A. a surface structure consisting of additional protective layers
B. no ribosomes
C. appendages in the form of flagella and pili
D. relatively high rates of respiration
E. relatively reduced resistance to boiling and desiccation 


32. A chemical substance found in bacterial endospores that is not found in vegetative cells is
A. diaminopimelic acid
B. dipicolinic acid
C. ketodeoxyoctonoic acid
D. D-glutamate
E. L-lysine 


33. Which of the following is not a function of the plasma membrane of procaryotes?
A. retention of cytoplasmic constituents as a selective permeability barrier
B. active transport of nutrients from the environment
C. storage of reserve carbohydrates and lipids
D. electron transport and O2 uptake during aerobic respiration
E. light harvesting and electron transport during photosynthesis 


34. The passage of molecules (solutes) across the bacterial plasma membrane from a region of low concentration to a region of high concentration is called
A. antiport (exchange diffusion)
B. facilitated diffusion
C. osmosis
D. group translocation
E. active transport 


35. Binding protein-dependent transport systems are used by bacterial cells to
A. pass hydrophilic molecules of low molecular weight through porins in the outer membrane
B. pass electrons through a sequence of carriers in the plasma membrane
C. secrete proteins across the plasma membrane into the periplasmic space
D. establish a proton motive force on the surface of the membrane
E. take up nutrients, such as sugars and amino acids, from the environment 


36. Transport of glucose using a group translocation system rather than a binding protein dependent transport system is advantageous to a bacterium because
A. glucose, a disaccharide, is initially cleaved into its monosaccharide constituents during the transport process
B. glucose can be transported into the cell against an external concentration gradient
C. glucose is phosphorylated as it traverses the membrane which accomplishes the first step of glycolysis and conserves ATP
D. energy is not required for transport
E. it has the effect of decreasing the internal osmolarity within the cytoplasm of the cell 


Questions 37-40 refer to the following diagram of the ultrastructure of the plasma membrane of Escherichia coli.


37. The lactose transport system (lactose permease) is an example of
A. a uniport process
B. an antiport process
C. a symport process
D. an ion-driven transport system
E. two of the above 


38. Proton motive force is established on the membrane by means of
A. lactose transport
B. ATP synthesis
C. electron transport processes in the membrane
D. Ca++ export
E. all of the above 


39. Proton motive force on the membrane is utilized during the process of
A. flagellar rotation
B. proline transport
C. ATP synthesis
D. Na+ export
E. all of the above 


40. Suppose you could inhibit the transmembranous ATPase enzyme of the bacterium without inhibiting the membrane electron transport system. Which effect(s) on the bacterium would you expect to encounter?
A. loss in ability to make ATP by electron transport phosphorylation
B. loss in ability to establish pmf on the membrane
C. loss in ability to transport sugars or amino acids using ion (proton)-driven transport systems
D. loss in the ability to swim
E. two of the above 


41. Some cyanobacteria are able to grow in the atmosphere, in the presence of light, in solutions that contain only a few mineral salts (tapwater, for example). Physiological (metabolic) characteristics that permit their growth under these conditions include
A. ability to fix CO2
B. ability to fix N2
C. ability to convert light energy into chemical energy
D. lack of any growth factor requirements
E. all of the above 


42. Which of the following statements regarding bacterial growth factors is not true?
A. They are needed as sources of carbon and energy by heterotrophic bacteria.
B. Although not proteins, they may be constituents of proteins.
C. Their need in bacterial nutrition results from a missing or blocked metabolic pathway.
D. They may function as vitamins or coenzymes in metabolism.
E. Growth factors are not required by all bacteria. 


43. In what type of bacterial culture medium listed below would blood never be a component?
A. an enrichment medium
B. a complex medium
C. a selective medium
D. a chemically-defined medium
E. a solid (as opposed to liquid) medium 


44. Lack of the enzymes catalase and superoxide dismutase may explain why certain bacteria are
A. unable to produce oxygen radicals when exposed to O2
B. able to grow in the absence of O2
C. killed by exposure to O2
D. able to respire in the presence of O2
E. able to respire in the absence of O2


45. An Archaean that is an obligate anaerobe and an extreme thermophile A. can grow at 37 degrees in the absence of O2
B. can grow at 37 degrees in the presence of O2
C. can grow at 85 degrees in the presence of O2
D. can grow at 85 degrees in the absence of O2
E. none of the above 


46. A bacterium that is a psychrotroph and a facultative anaerobe
A. can grow at 5 degrees in the absence of O2
B. can grow at 5 degrees in the presence of O2
C. can grow at 25 degrees in the presence of O2
D. all of the above
E. none of the above 


47. A procaryote, Halobacterium in the Great Salt Lake, requires NaCl in excess of 4 molar in order to grow, and is therefore classified nutritionally as a(n)
A. alkalophile (alkaliphile)
B. lithotroph
C. phototroph
D. extreme halophile
E. extreme thermophile 


Questions 48-50 refer to the following set of data.

A standard bacterial growth curve can be plotted from the following information:

A bacterium was inoculated into fresh broth medium and incubated at 37 degrees under aerobic conditions. Viable cell counts (plate counts) over a period of 24 hours resulted in findings of 100 cells/ml at the time of inoculation, 100 cells/ml at 2 hours, 100 cells/ml at 4 hours, 103 cells/ml at 6 hours, 104 cells/ml at 8 hours, 106 cells/ml at 12 hours, 108 cells/ml at 16 hours, 109 cells/ml at 18 hours, 109 cells/ml at 20 hours, 109 cells/ml at 22 hours, 108 cells/ml at 24 hours. 


48. What coordinates are used to label the graph that plots the bacterial growth curve?
A. growth rate vs time
B. growth rate vs generation time
C. optical density vs time
D. number of bacteria vs time
E. log number of viable cells vs time 


49. The length of the lag phase of the culture is
A. 2 hours
B. 4 hours
C. 8 hours
D. 14 hours
E. 18 hours 


50. The generation time of this bacterial culture is approximately
A. 18 minutes
B. 30 minutes
C. 36 minutes
D. 48 minutes
E. 72 minutes


51. Pasteurization of milk using heat accomplishes
A. complete elimination of all microorganisms in the milk
B. reduction in the total number of organisms but no reduction or elimination of pathogens in the milk
C. elimination of pathogens but no elimination or reduction in the number of nonpathogens in the milk
D. killing all potential pathogens in milk except Mycobacterium tuberculosis
E. reduction in the total number of microorganisms and elimination of potential pathogens in the milk


52. The temperature and time necessary to sterilize a substance in the autoclave is
A. 72 degrees/30 minutes
B. 100 degrees/30 minutes
C. 121 degrees/15 minutes
D. 160 degrees/2 hours
E. 180 degrees/1 hour


53. The pore diameter of membrane filters used in sterilization processes, selected because it is the largest pore diameter that will exclude passage of bacterial cells, is:
A. 0.22 millimeter
B. 12.1 micrometers
C. 1.0 micrometer
D. 0.45 micrometer
E. 0.22 micrometer


54. Chemical antiseptics are
A. bactericidal agents harmless to human tissues and mucous membranes
B. bacteriostatic agents that act as chemical analogs of bacterial metabolites
C. synthetic chemicals used in the treatment of infectious disease
D. natural substances that may be bactericidal or bacteriostatic depending on their concentration
E. bactericidal agents useful on inanimate objects only


55. An inherent distinction between a chemical disinfectant and a chemical food preservative depends upon
A. concentration of the substance in order to be effective
B. whether the substance is a cidal agent or a static agent
C. whether the substance must be continually present in order to be effective
D. whether the substance is of synthetic or natural origin
E. two of the above


56. Two important features of bacterial cells that make them selective targets for the action of most clinically-useful antibiotics are
A. absence of mitochondria and chloroplasts
B. cell wall composition and ribosome structure
C. presence of saturated fatty acids and absence of sterols in membranes
D. DNA (chromosome) structure and absence of a nuclear membrane
E. size and type of nutrition


57. Chemical modification of the substituent groups of a naturally-produced beta lactam molecule leads to the industrial development of
A. semisynthetic penicillins
B. sulfa drugs
C. tetracyclines
D. chloramphenicol
E. beta lactamase enzymes


58. Identify the common mechanism of action of the aminoglycoside, macrolide and tetracycline antibiotics in bacterial cells.
A. growth factor analogs that interfere with procaryotic vitamin metabolism
B. disruption of the outer membrane of Gram-negative bacteria
C. interference with transcription
D. inhibition of cell wall synthesis
E. interference with translation


59. The selective toxicity of rifamycin is achieved on this basis.
A. It specifically inhibits an enzyme involved in an early step in the synthesis of bacterial murein.
B. It combines with yeast sterols (ergosterol) and thereby disrupts membranes.
C. It binds selectively to the bacterial ribosome and blocks peptide bond formation between amino acids during the translation process.
D. It transfers ADP-ribose from NAD to eukaryotic Elongation Factor 2 thereby inhibiting its activity during protein synthesis.
E. It blocks the activity of bacterial, but not eukaryotic, RNA polymerase


60. Gram-negative bacteria are typically less susceptible to the effects of natural penicillin than are Gram-positive bacteria because
A. they lack a transport system for penicillin
B. they degrade penicillin in the periplasmic space by means of penicillinase enzymes
C. they lack peptidoglycan in their cell wall
D. their peptidoglycan is chemically modified to be resistant to attack by penicillin
E. their outer membrane is an effective permeability barrier


61. Proton motive force (pmf) or membrane potential established on the bacterial membrane can be utilized by bacterial cells to
A. transport solutes
B. rotate the bacterial flagellum
C. synthesize ATP
D. all of the above
E. none of the above


62. Coupling proton motive force to the synthesis of ATP is a characteristic of all of the following types of bacterial metabolism except
A. lithotrophy
B. phototrophy
C. fermentation
D. aerobic respiration
E. anaerobic respiration


63. What pathway of glycolysis is utilized by Clostridium acetobutilycum during the fermentation of carbohydrates that yields end products acetone and butanol?
A. Embden-Meyerhof
B. Entner-Doudoroff
C. Phosphoketolase
D. mixed acid pathway
E. mixed acid plus butanediol pathway


64. Which two pathways below, which proceed through the Embden-Meyerhof type of fermentation, are found in the enteric bacteria (e.g. E. coli and Klebsiella) and in the genus Bacillus?
A. heterolactic pathway
B. mixed acid
C. mixed acid plus butanediol pathway
D. A and B
E. B and C


65. Zymomonas utilizes the Entner-Doudoroff pathway to ferment glucose in the following overall reaction: Glucose ____________>2 ethanol + 2 CO2. During this pathway of glucose utilization_____mole(s) of ATP are utilized and_____mole(s) of ATP (total) are produced.
A. 1, 2
B. 2, 1
C. 2, 3
D. 2, 4
E. 3, 4


66. During the fermentation of Swiss cheese, bacteria utilize the end products of lactate fermentation to form these distinct end products.
A lactate, ethanol and CO2
B. succinate, ethanol and CO2
C. butyric acid and acetone
D. propionate, acetate and CO2
E. hydrogen and CO2


67. The oxidation of NO2 ____________> NO3 is a(n)________________________form of metabolism conducted by Nitrobacter, while the reduction of NO3 ____________> NO2 is a(n)________________________type of metabolism conducted by Pseudomonas and Bacillus.
A. lithotrophic, aerobic
B. anaerobic, lithotrophic
C. lithotrophic, anaerobic
D. anaerobic, aerobic
E. aerobic, lithotrophic


68. Lithotrophic oxidations include all of the following except
A. H2 ____________> 2H2O
B. NH3 ____________> NO2
C. CO2 ____________> CO
D. H2S ____________> SO4
E. none of the above (all are lithotrophic oxidations)

Questions 69-73 refer to the following sequences of reactions from bacterial metabolic pathways.

 


69. Reaction A is a characteristic of the
A. Embden-Meyerhof pathway
B. Entner-Doudoroff pathway
C. Heterolactic pathway
D. two of the above
E. all of the above


70. The sequence of reactions in B occurs during the
A. Embden-Meyerhof pathway
B. Entner-Doudoroff pathway
C. phosphoketolase pathway
D. all of the above
E. none of the above


71. The sequence of reactions in C occurs during the
A. Embden-Meyerhof pathway
B. Entner-Doudoroff pathway
C. phosphoketolase pathway
D. all of the above
E. none of the above


72. In which set of reactions is the bacterial enzyme phosphoketolase involved?
A. A
B. B
C. C
D. D
E. E


73. What group of bacteria utilize Reaction E during fermentation?
A. Homoloactic acid bacteria
B. Heterolactic acid bacteria
C. Propionic acid bacteria
D. Pseudomonads
F. Clostridia


Questions 74-79 refer to the following metabolic pathway: The overall reaction for the fermentation of glucose by a lactic acid bacterium is given in the pathway below. Numbers refer to the individual enzymatic reactions of the pathway.


74. The enzyme that is diagnostic for this fermentation pathway (that distinguishes it from other types of glycolysis or fermentation) is
A. phosphoketolase
B. fructose 1,6-diphosphate aldolase
C. KDPG aldolase
D. RUBP carboxylase
E. beta galactosidase


75. Reactions 2 and 7 in this pathway are________________ .
A. isomerizations
B. decarboxylations
C. oxidations
D. reductions
E. phosphorylations


76. The oxidation reaction that is mediated by the coenzyme NAD is reaction number________ .
A. 1
B. 4
C. 5
D. 6
E. 10


77. The reduction reaction that is mediated by NADH2 is reaction number________ .
A. 4
B. 5
C. 6
D. 9
E. 10


78. Substrate-level phosphorylation that leads to the synthesis of ATP occurs at reaction________ .
A. 1
B. 3
C. 6
D. 10
E. two of the above


79. Assuming that the bacterium transported the glucose using a binding protein-dependent transport system which utilized ATP for transport, what would be the net gain in ATP per mole of glucose obtained by this fermentation?
A. 1 mole
B. 2 moles
C. 3 moles
D. 4 moles
E. none of the above


Questions 80-84. Glycerol can be utilized in the following manner as a sole source of energy by an aerobically-respiring Bacillus.
1. Glycerol is transported by a facilitated diffusion system (a glycerol uniporter system which does not require energy for transport).
2. Following uptake, glycerol is immediately phosphorylated by a kinase enzyme which utilizes ATP (Step 1 below).
3. Glycerol phosphate is oxidized by NAD to yield Glyceraldehyde-phosphate (Step 2 below) which is subsequently metabolized by enzymes of the Embden-Meyerhof pathway and the TCA cycle (Steps 3-16 below) to yield 3 moles of CO2 per mole of glycerol. All electrons removed during the oxidation of glycerol are entered into a conventional aerobic electron transport system and ATP is produced by oxidative phosphorylation. In this type of Bacillus respiration, P/O = 3 (i.e., 3 ATP are produced per pair of electrons entered into the ets by NADH2). This pathway may be written as follows:


80. Substrate-level phosphorylations that lead to the synthesis of ATP (or GTP) occur at reactions________ .
A. 1 and 3
B. 1, 2, and 3
C. 4 and 5
D. 5 and 13
E. 4, 7, and 13


81. Which sequence below correctly lists all reactions in the pathway where NADH2 is produced?
A. 2, 3, 8, 11, 12, 16
B. 2, 3, 8, 11, 12, 14, 16
C. 2, 11, 12, 15
D. 2, 11, 12, 14, 15
E. none of the above


82. What is the net gain in ATP per mole of glycerol utilized by the bacterium during this respiration when O2 is used as the final electron acceptor?
A. 1 mole
B. 14 moles
C. 18 moles
D. 22 moles
E. none of the above


83. What are the end products of this type of metabolism when O2 is utilized as the final electron acceptor?
A. Acetyl CoA and Oxaloacetate
B. Alpha-ketoglutarate, Succinate and Oxaloacetate
C. H2 and CO2
D. H2O and CO2
E. ATP and NADH2


84. If NO3 was the respiratory electron acceptor in this type of metabolism (in place of O2), in a denitrifying Bacillus, the end products of respiration would be
A. CO2 and H2O
B. CO2 and NO2
C. H2 and CO2
D. H2 and N2
E. H2O and NH3


85. Among procaryotes oxygenic photosynthesis is a characteristic of
A. Purple bacteria
B. Cyanobacteria
C. halobacteria
D. Green bacteria
E. none of the above


86. Components of the photosynthetic electron transport system of the Purple and Green bacteria include all of the following except
A. ferredoxin
B. bacteriochlorophyll
C. quinones
D. cytochromes
E. none of the above (all are components of the photosynthetic ets)


87. The light reactions of photosynthesis in the Cyanobacteria involve all of the following except
A. photosystem I
B. photosystem II
C. chlorophyll a
D. H2O
E. H2S


88. During CO2 fixation involving RUBP carboxylase and the Calvin cycle, how many moles of NADPH2 are required to reduce one mole of CO2 to carbohydrate?
A. 1
B. 2
C. 4
D. 10
E. 12


89. The methanogens use the ________________ and the Green bacteria use the ________________ in order to fix CO2 for growth.
A. enzyme carbon monoxide dehydrogenase ________ enzyme RUBP carboxylase
B. conventional TCA cycle ________ reverse TCA cycle
C. enzyme carbon monoxide dehydrogenase ________ reverse TCA cycle
D. enzyme RUBP carboxylase ________ enzyme RUBP carboxylase
E. enzyme RUBP carboxylase ________ enzyme carbon monoxide dehydrogenase



90. Photoautotrophic growth in the purple sulfur bacteria involves all of the following except
A. bacteriochlorophylls as primary pigments absorbing light in the range of 800-1000nm
B. CO2 fixation utilizing RUBP carboxylase and the Calvin cycle
C. phycobilins as secondary light harvesting pigments
D. an electron transport system consisting of cytochromes and quinones
E. ATP synthesis utilizing a transmembranous ATPase enzyme


91. An important role of carotenoids, besides acting as light-harvesting pigments, in all photosynthetic organisms involves
A. reducing superoxides to peroxides similar to superoxide dismutase
B "quenching" singlet oxygen, thereby preventing harmful photooxidations in cells
C. transferring electrons in the photosynthetic electron transport system
D. providing electrons to photosystem I for reduction of ferredoxin
E. all of the above


92. The Calvin Cycle is not an amphibolic pathway because it
A. does not provide energy
B. produces ATP by substrate level phosphorylation
C. does not provide intermediates for biosynthesis
D. does provide metabolic intermediates for biosynthesis
E. none of the above


93. A promoter at the beginning of a genetic operon is a(n)
A. enzyme that facilitates the transcription of DNA
B. site where DNA replication begins
C. site on DNA where RNA polymerase binds
D. site on RNA where translation starts
E. gene that codes for RNA polymerase


94. The operator region of an associated operon
A. codes for the synthesis of a repressor
B. is a nucleotide sequence of DNA that binds an active regulatory protein
C. binds RNA polymerase at the beginning of transcription of an operon
D. is a nucleotide sequence of an RNA molecule which is not translated into protein
E. none of the above


95. Possession of the lac operon and its control elements provides for E. coli
A. ability to transport and utilize lactose as an energy source when the sugar is available in the environment
B. ability to regulate transcription of the lactate dehydrogenase gene
C. a pathway of mixed acid fermentation with lactic acid as a primary end product
D. a genetic means to stop making lactose if it detects it in its environment
E. two of the above


96. In E. coli, when the lac operon is fully induced (in the presence of lactose)
A. the lac repressor is active and transcription of the lac operon does not occur
B. the lac repressor is inactive and transcription of the lac operon does occur
C. lactose cannot be transported by the cells
D. lactose cannot be cleaved to enter glycolysis
E. none of the above


97. In a repressible pathway (e.g. tryptophan biosynthesis), in the presence of the effector molecule (i.e., tryptophan), the repressor protein is
A. active and can bind to the operator site
B. active and cannot bind to the operator site
C. inactive and cannot bind to the operator site
D. inactive and can bind to the promoter site
E. able to inhibit the activity of the first enzyme unique to the pathway of biosynthesis


Questions 98 - 100 refer to the plot below which illustrates growth (as optical density) of Escherichia coli in a minimal medium with limiting amounts of glucose and lactose as sole sources of carbon and energy.


98. During what period of time do the bacteria utilize glucose as a carbon-energy source?
A. 0-2 hours
B. 2-8 hours
C. 2-16 hours
D. 8-10 hours
E. 10-20 hours


99. The transcription of the beta-galactosidase and lactose permease genes begins at
A. 0 hours
B. 2 hours
C. 8 hours
D. 10 hours
E. 20 hours


100. During what period of time do the bacteria utilize lactose as their sole source of carbon and energy?
A. 0-2 hours
B. 2-8 hours
C. 8-10 hours
D. 10-20 hours
E. 20-28 hours



101. Resistance transfer factors (RTFs) in E. coli are
A. insertion elements on the F factor
B. transmissible plasmids that encode genes for drug resistance
C. genes that move from place to place on the bacterial chromosome
D. outer membrane proteins that exclude passage of antibiotics and
hydrophobic agents
E. plasma membrane proteins that mediate the passage of solutes into and out
of the cell



102. In the Griffith experiment, the substance present in the suspension of
heat-killed virulent cells of Streptococcus pneumoniae that, when mixed with
living non virulent cells, transformed them into living virulent cells was
A. DNA
B. capsular material from the virulent cells
C. mouse phagocytes
D. RNA
E. Spn toxin



103. In the Zinder and Lederberg U-tube experiment , DNAase was added to the
U-tube to inhibit the process of
A. translation
B. transformation
C. lysogeny
D. conjugation
E. transduction



104. The penicillin enrichment technique is useful when isolating auxotrophic mutants (for example Trp-) because penicillin
A. prevents the growth of wild type bacteria but not mutants
B. does not affect eukaryotic cells
C. kills only the growing bacterial cells, not the mutants in the population
D. increases the rate of mutation toward auxotrophy
E. does not affect E. coli under the conditions of the procedure



105. Trp- mutants (tryptophan auxotrophs) can be isolated by
A. direct plating on medium containing tryptophan
B. direct plating on medium without tryptophan
C. replica plating from a medium without tryptophan to a medium with tryptophan
D. replica plating from a medium with tryptophan to a medium without tryptophan
E. none of the above



106. Lys+ revertants (prototrophs) could be isolated from a population of lys- mutants by
A. direct plating on medium containing lysine
B. direct plating on medium without lysine
C. replica plating from a medium without lysine to a medium with lysine
D. two of the above
E. none of the above



107. A bacterial geneticist mixes together 108 cells which require methionine and
are ampicillin sensitive and 108 cells which require phenylalanine and tyrosine
and are ampicillin resistant. In order to detect whether genetic recombination
had occurred between the two strains it would be best to grow the mixture of
cells in
A. minimal glucose medium with no supplements
B. minimal glucose medium plus methionine and phenylalanine
C. minimal glucose medium plus methionine, phenylalanine and tyrosine
D. minimal glucose medium plus phenylalanine, tyrosine and ampicillin
E. minimal glucose medium plus ampicillin



108. Before mixing these strains together the geneticist (above) plates 108 cells of the auxotroph that requires methionine and is ampicillin-sensitive onto minimal glucose medium with no supplements. Approximately 100 colonies arise on the plate. The geneticist concludes that
A. the rate of reversion to methionine prototrophy is 10-6
B. the rate of mutation to ampicillin resistance is 10-6
C. the combined rate of reversion methionine prototrophy and mutation to ampicillin resistance is10-12
D. all of the above
E. none of the above



109. Two strains of Salmonella are mixed, one which is arg-, his -, cob- and CMr, and the other which is cob-, thi-, and CMs. In order to determine if genetic recombination takes place between these organisms which medium would you plate the mixture of cells on in order to detect the recombinants?

arg = arginine
cob = cobalamin (vit B12)
his = histidine
thi = thiamin (vit B1)
CM = chloramphenicol (r = resistant; s = sensitive)

A. Glucose minimal medium plus cob, arg
B. glucose minimal medium plus cob, thi
C. glucose minimal medium plus cob, his
D. glucose minimal medium plus his, thi, CM
E. glucose minimal medium plus cob, CM



110. A molecular biologist extracts the DNA from a lactose positive (Lac+) strain of E. coli and a penicillin-resistant (PCr) strain of S. aureus . Using restriction enzymes and DNA ligases, she cuts and joins together fragments of the DNA derived from the two organisms, hoping that the lac gene of E. coli will recombine with the PC resistance gene of S. aureus. She uses a process of artificial transformation to insert (transform) the DNA fragments into a E. colistrain which is penicillin-sensitive (PCs) and lactose-negative (Lac-). What medium should she plate the transformants on in order to select for a penicillin-resistant, lactose positive recombinant?
A. minimal medium plus glucose
B. minimal medium plus penicillin and lactose
C. minimal medium plus penicillin and glucose
D. minimal medium plus lactose
E. none of the above



111. During the process of generalized transduction
A. cell to cell contact is required
B. a bacteriophage capsid can enclose and transfer any part (gene) of the
bacterial chromosome
C. the transfer of DNA is inhibited in the presence of DNAase
D. the recipient must be susceptible to infection by the same bacteriophage as
the donor
E. two of the above



112. During the process of restricted (specialized) transduction
A. lysogenic bacteriophages are required
B. exclusively genes linked to the prophage DNA are transferred from a donor
to recipient
C. the prophages are occasionally able to replicate and lyse their host cell
D. all of the above
E. none of the above



113.  One reason that guarantees viruses must exist exclusively as obligate intracellular parasites is
 A.  they lack a genome
 B.  they lack any way to protect their nucleic acids from extracellular nucleases
 C.  they require host cell DNA for transcription into viral RNA
 D.  they require host cell mRNAs for translation into viral proteins
 E.  they require host ribosomes for translation of viral proteins



114.  The tail and related structures of a bacteriophage such as T2 or lambda
 A.  are composed of proteins distinct from capsomere proteins
 B.  are involved in attachment and penetration of viral DNA
 C.  may package the enzyme lysozyme for involvement in infection
 D.  are encoded by viral (as opposed to host) genes
 E.  all of the above



115.  During bacteriophage replication in a susceptible cell the "early proteins" translated from viral "early mRNA" are concerned with
A.  adsorption of the phage to the host cell wall receptor
 B. replication of the viral nucleic acid
 C.  synthesis of coat proteins
 D.  assembly of capsomeres
 E.  lysis of the host cell



116.  During the replication of a lytic bacteriophage in its specific host cell the "late proteins" are concerned with
 A.  replication of the virus nucleic acid
 B.  viral assembly and escape from its host cell
 C.  conversion of viral RNA into a complementary copy of DNA
 D.  integration of virus DNA into the host cell chromosome
 E.  both C and D



117.  In both lysogeny of a bacterial cell by a temperate virus and transformation of an animal cell by an oncogenic virus, the infected cell
 A.  converts from a normal cell into a tumor cell
 B.  expresses a new cell phenotype as a result of infection by viral DNA
 C.  maintains viral DNA within its chromosome
 D.  lyses as a result of virus infection
 E.  represses the synthesis of all viral proteins



118.  In the process of lysogenic conversion of a bacterial cell (e.g. lysogeny of Corynebacterium diphtheriae  by phage Beta) and transformation of an animal cell by a retrovirus (e.g. infection of T cells by HIV) the infected cell
 A.  expresses a new cell phenotype as a result of infection by a virus
 B. converts from a normal cell into a tumor cell by loss of contact inhibition
 C.  lyses as a result of virus infection
 D.  loses the ability to reproduce due to viral inhibition of host cell DNA replication
 E.  all of the above.



119. In bacterial genetics the term competence refers to a bacterium with
A. ability to be transformed
B. the F factor integrated into its chromosomal DNA
C. susceptibility to lytic infection by bacteriophage
D. susceptibility to lysogenic infection by bacteriophage
E. ability to act as a DNA donor during transformation



120. Which of the following statements is true of the natural transformation
systems of both Haemophilus and Streptococcus?
A. The process was observed by Griffith more than a decade preceding the
discovery of DNA as the transforming principle.
B. The transformation system is genetically-encoded by bacterial chromosomal
DNA.
C. Highly artificial treatment of cells, such as exposure to high concentrations of
divalent cations, is an absolute requirement for transformation to occur.
D. Competence involves formation of membranous "blebs" in the Gram-negative
outer membrane of the recipient.
E. DNA enters the cell in a membranous transformasome.



121. Comparing the transformation processes of E. coli, Streptococcus and
Haemophilus, which of the following statements is true of Haemophilus only?
A. Transforming DNA is protected in the virus coat from extracellular DNAases
as it passes from the donor to the recipient.
B. Only homologous DNA, with a unique 11 base pair sequence, is taken up by
the recipient cells.
C. A protein called competence factor must be produced in a critical
concentration to trigger cellular ability to take up transforming DNA.
D. Transforming DNA is bound to the recipient cell surface in a double-stranded
form but enters the cell as single-stranded DNA.
E. DNA from any source may be taken up by the recipient cells.


122. The largest density (greatest number) of bacteria on the surfaces of the human body is found on (in) the
A. skin
B. lower gastrointestinal tract
C. stomach
D. lower respiratory tract
E. mouth 


123. The predominant bacterium in the lower GI tract (colon) of adults is
A. Bifidobacterium
B. E. coli
C. Bacteroides
D. Enterococcus faecalis
E. Methanobacter


124. The most important benefit that the human gastrointestinal flora provide for their host is
A. digestion of dietary cellulose
B. a low grade toxemia
C. production of dietary protein
D. antagonism against colonization by potential pathogens
E. production of antibodies 


125. The main carrier site on the human body for strains of potentially pathogenic Staphylococcus aureus is the
A. oral cavity
B. throat (posterior nasopharynx)
C. nasal membranes
D. gastrointestinal tract
E. vagina 


126. The carrier site for pathogenic Neisseria meningitidis is the
A. conjunctiva
B. nasopharynx
C. urogenital tract
D. blood
E. meninges 


127. This bacterium, although usually not considered as normal flora, frequently colonizes the stomach and is thought to be the cause of gastric and duodenal ulcers.
A. Lactobacillus acidophilus
B. Pseudomonas aeruginosa
C. Escherichia coli
D. Vibrio cholerae
E. Helicobacter pylori


128. Silver nitrate or an antibiotic is put into the eyes of newborn infants to prevent infection by
A. Doderlein's bacillus (Lactobacillus acidophilus)
B. Herpes simplex virus
C. Neisseria gonorrhoeae
D. Chlamydia trachcomatis
E. two of the above 


129. A characteristic of Streptococcus mutans that allows it to initiate dental plaque and dental caries is:
A. the ability to attach specifically to the pellicle of the tooth
B. the ability to utilize sucrose as a source of carbon and energy
C. the ability to produce a dextran capsule
D. the ability to produce lactic aci
E. all of the above 


130. The fimbriae of enterotoxigenic E. coli are essential to the bacterium when it causes disease because
A. they are needed for initial attachment of the bacteria to the gastrointestinal epithelium
B. they activate host adenylate cyclase enzymes leading to disruption of cellular permeability
C. they make the bacteria resistant to phagocytic killing and digestion by white blood cells
D. they convert GI tract components (bile) to substances which provoke
symptoms of disease
E. they allow the bacteria to swim "upstream" against the peristaltic action of the GI tract thereby remaining established in the GI tract 


131. The fibrin coat that can be formed by coagulase-positive staphylococci and the hyaluronic acid capsule of Streptococcus pyogenes are pathogenic strategies to
A. promote colonization of a host
B. cause direct damage to host cells during pathogenesis
C. hide bacterial antigens from the host immune tissues
D. survive as intracellular parasites
E. alter or change their surface antigens within the course of an infection 


132. Leukocidins are
A. enzymes contained in the lysosomes of phagocytes to kill ingested bacteria
B. proteins produced by bacteria that kill closely-related bacteria
C. proteases produced by bacteria which destroy host immunoglobulins
D. enterotoxins produced by Staphylococcus aureus involved in food-borne disease
E. substances produced by pyogenic bacteria that kill phagocytes 


133. The streptococcal invasin which behaves as a "spreading factor" by breaking down the framework of connective tissues is called
A. collagenase
B. streptokinase
C. streptolysin
D. erythrogenic toxin (pyogenic exotoxin)
E. hyaluronidase 


134. A primary determinant of virulence in Streptococcus pyogenes, which is involved in adherence, resistance to phagocytosis and antigenic variation, is
A. streptokinase
B. lipopolysaccharide (endotoxin)
C. M-protein
D. Protein A
E. coagulase 


135. Which of the following statements that relate to bacterial exotoxins and endotoxins is true?
A. Exotoxins are proteins; endotoxins are lipopolysaccharides.
B. Exotoxins are typically structural (cell wall) components of Gram-positive bacteria.
C. Endotoxins can never be released by the cells that produce them.
D. Endotoxins cause their toxicity through an enzymatic mechanism of action.
E. In the host, endotoxins are destroyed by the enzyme lysozyme. 


136. The substrate for the enzymatic (A) component of diphtheria toxin and the cholera toxin is
A. NAD
B. cyclic AMP
C. the regulatory proteins of the eukaryotic adenylate cyclase complex
D. ATP
E. elongation factor 2 (EF-2) 


137. The large volume of fluid lost by diarrhea during infection with Vibrio cholerae
A. is a consequence of fluid replacement during treatment of the disease and does not result directly from activity of the cholera toxin
B. results from electrolytes binding to the intestinal enterocytes which upsets their water retention capability
C. is caused when the vibrios bind to the intestinal epithelium and physically or mechanically block the uptake of fluids by the gut epithelial cells
D. follows activation of adenylate cyclase by cholera toxin and the subsequent effect of cyclic AMP on water and salt balances of the host cells
E. results from neurotoxic effects of the cholera toxin on the central nervous system 


138. The similarity between the toxic shock syndrome toxin (TSST), the staph enterotoxins, and the erythrogenic toxin (pyogenic exotoxin) is
A. they are all produced by Staphylococcus aureus
B. they stimulate the immune system in a similar manner as superantigens
C. the pathology of the diseases that they cause is identical
D. they are all neurotoxins
E. they are the same (identical) toxin produced by three different organisms 


139. Both the botulinum toxin and the tetanus toxin
A. are produced by Bacillus anthracis
B. act in the central nervous system
C. act in the peripheral nervous system
D. are Zn++ dependent protease enzymes
E. two of the above 


140. Two bacterial toxins which behave as adenylate cyclase enzymes (i.e., are inherent adenylate cyclase enzymes) in eukaryotic cells are
A. cholera toxin and pertussis Ptx toxin
B. pertussis AC toxin and Anthrax EF toxin
C. staphylococcal TSST and staphylococcal enterotoxin
D. diphtheria toxin and Pseudomonas exotoxin A
E. staphylococcal leukocidin and streptococcal streptokinase 


141. The characteristic substance in the core (R) region of the endotoxin molecule that is often assayed (measured) to determine the presence of bacterial endotoxin in a biological substance is
A. ketodeoxyoctonoic acid (KDO)
B. N-acetylmuramic acid (NAM)
C. Lipid A
D. dideoxyhexose
E. N-acetylglucosamine (NAG) 


142. Injection of endotoxin into an animal stimulates the following response(s):
A. an immunological response resulting in antibody production
B. an inflammatory response resulting in fever
C. activation of complement leading to inflammation
D. activation of the Hageman factor leading to intravascular coagulation and hemorrhage
E. all of the above 


143. The portion of the endotoxin molecule that is believed to be responsible for most of its toxic properties is
A. lipid A
B. core polysaccharide
C. specific "O" polysaccharide
D. B +C
E. A + B + C 


144. Active immunity against diphtheria is accomplished by
A. administration diphtheria antitoxin or antiserum
B. immunization with the diphtheria toxoid
C. recovery from the disease diphtheria
D. transfer of antibodies from mother to offspring via the colostrum (milk)
E. two of the above 


145. Passive immunity to tetanus in a susceptible host would be accomplished by
A. recovery from the disease tetanus
B. injection with tetanus toxin
C. injection with tetanus toxoid (as in the DTP vaccine)
D. administration of serum from an individual with active immunity to tetanus
E. two of the above 


146. A newborn infant is passively immune due to
A. transplacental transfer of maternal antibodies in utero
B. exposure to foreign antigens during birth
C. activation of the immune system which occurs at birth
D. immediate colonization by a normal flora
E. recovery from diseases acquired after birth 


147. Bacterial substances that are antigenic to an animal
A. typically have a high molecular weight (>10,000 daltons)
B. will cause the formation of antibodies
C. are often the surface components of the bacterial cells
D. are "foreign" molecules to the animal
E. all of the above 


148. The type of cell in an animal that is the precursor of phagocytes and
lymphocytes is
A. bone marrow stem cell
B. lymphoblast
C. monocyte
D. B cell
E. pre T cell 


149. During a primary immune response antibody molecules (immunoglobulins) are synthesized by
A. T cells
B. B cells
C. macrophages
D. plasma cells
E. none of the above 


150. The predominant immunoglobulin in the serum of an animal is
A. IgA
B. IgD
C. IgE
D. IgG
E. IgM 


151. The most important activity of IgA on the surface of the intestinal or respiratory mucosa is to
A. stimulate the development of an immune response
B. activate an inflammatory response
C. block colonization of the surfaces by pathogens
D. stimulate the development of a T-cell response
E. block the production of IL-1 by macrophages 


152. Circulating antibody molecules participate in anti-bacterial host defense by
A. opsonizinzation of bacterial cells
B. activation of complement on the bacterial surface
C. agglutination (immobilization) of bacterial cells
D. neutralization bacterial toxins
E. all of the above 


153. The function of cytotoxic T cells (TC) during an immunological response is to
A. act as antigen presenting cells for the induction of the immune response
B. kill cells which show a new antigen on their surface
C. produce lymphokines that activate macrophages
D. produce IL-2 that stimulates the development of T cells
E. none of the above 


154. The main function of interleukin-l (IL-l) during an immunological response is to
A. cause fever and inflammation
B. stimulate TH2 cells
C. stimulate macrophages
D. enhance phagocytosis
E. induce differentiation of B cells into plasma cells 


155. Which of the following cell types is not involved in the initiation and mediation of the antibody-mediated immune (AMI) response?
A. macrophages (as antigen presenting cells)
B. B-lymphocytes
C. plasma cells
D. TC cells
E. TH2 cells 


156. The cell-mediated immune (CMI) response is responsible for
A. killing cells infected by viruses
B. killing tumor cells
C. rejection of tissue transplants
D. all of the above
E. none of the above