Microbiology 2124
Final Exam
May 7, 1999
David Demezas

General Instructions: Choose the most correct answer and mark the corresponding letter on your scantron answer sheet. The key will be posted by my door and on the web later today, so you may wish to record your answers on your test to grade it.

1. The criteria used to relate a specific microbe to a specific infectious disease (the germ theory of disease) were established by ________ in the last century.
A. Pasteur
B. Petri
C. Hooke
D. Koch
E. Leeuwenhoek

2. Which of the following domains do not have a membrane bound nucleus?
A. Archaea
B. Bacteria
C. Eukarya
D. Both A and B
E. Both B and C

3. Which of the following is not a feature of the plasma membrane?
A. It is composed of phospholipids arranged in a lipid bilayer.
B. Integral proteins are embedded in the plasma membrane.
C. The peptidoglycan layer is an integral part of the plasma membrane.
D. It is selectively permeable.
E. It is a fluid structure.

4. Which of the following is not found in the peptidoglycan layer of a bacterium?
A. N-acetyl glucosamine
B. N-acetyl muramic acid
C. pyruvate
D. amino acids
E. All of the above are found in the peptidoglycan layer.

5. Which of the following is not a general feature of active transport?
A. Requires a carrier protein
B. Requires a form of energy
C. Can move molecules against a concentration gradient
D. All of the above are characteristic of active transport

6. The pathway that yields pyruvate from glucose is called ________.
A. Krebs cycle
B. glycolysis
C. gluconeogenesis
D. Tricarboxylic acid cycle
E. Calvin cycle

7. The majority of the ATP generated from aerobic respiration results directly from ______.
A. substrate level phosphorylation
B. the oxidation of NADH + H⁺
C. oxidative phosphorylation
D. the TCA cycle (syn. Krebs or citric acid cycle)
E. glycolysis

8. Which of the following statements about the proton motive force is false?
A. It is composed of a pH gradient and electrochemical potential.
B. The proton motive force is generated as electrons move down an electron transport chain and protons are extruded out of the cell.
C. The cytoplasm of the cell becomes more acidic.
D. The proton motive force can be used to drive ATP synthesis using ATP synthase.
E. All of the above statements are true.

9. The flow of electrons down the electron transport chain generates a proton motive force yielding ATP in all of the following except ________.
A. aerobic respiring bacteria
B. chemolithotrophs
C. anoxygenic phototrophs
D. fermentative bacteria and yeasts
E. oxygenic phototrophs

10. Which of the following statements about facultative aerobes is correct?
A. They can grow in the presence of a suitable electron acceptor, e.g., nitrate, in an anaerobic environment.
B. They are extremely sensitive to even the smallest amounts of oxygen.
C. They require oxygen for growth.
D. They use only substrate level phosphorylation to make ATP.
E. They are strictly fermentative organisms.

11. The above figure best illustrates the cell wall of _________.
A. a Gram negative bacterium
B. a protozoa
C. fungi
D. an Archaean cell
E. a Gram positive bacterium

12. The rigidity and shape of a bacterium is due to the _______.
A. cell membrane
B. peptidoglycan layer
C. lipopolysaccharide
D. teichoic acid layer
E. none of the above

13. True (A) or False (B). Given the above table and the following chemical equation: H₂ + 1/2 O₂ ------> H₂O. H₂ is the electron donor and O₂ is the electron acceptor.

14. Anoxygenic phototrophic bacteria generate ATP using _________ .
A. non cyclic photophosphorylation
B. oxidative phosphorylation
C. cyclic photophosphorylation
D. substrate level photophosphorylation
E. substrate level phosphorylation

15. ________ use light as an energy source and organic compounds as their carbon source.
A. Photoautotrophs
B. Chemolithotrophs
C. Photoheterotrophs
D. Chemoorganotrophs
E. Chemoautotrophs

16. Components of the electron transport chain is located in the ________.
A. cytoplasm of the cell
B. peptidoglycan layer
C. lipopolysaccharide layer
D. periplasmic space
E. plasma membrane

17. The first person to see microorganisms using crude, hand-crafted microscopes was ____________.
A. Hooke
B. van Leeuwenhoek
C. Winogradsky
D. Pasteur
E. Koch

18. Autotrophic CO₂ fixation to organic matter in autotrophic bacteria is a function of the _______.
A. Krebs cycle
B. glycolytic pathway
C. Calvin cycle
D. electron transport chain
E. fermentative pathway

19. True (A) or False (B): Sulfate respiration occurs in aerobic environments (i.e., oxic environments)

20. True (A) or False (B): A simple majority (i.e., >51%) of all species of microorganisms cause disease.

21. The time required for the formation of two cells from one cell is called _____.
A. the generation time
B. the doubling time
C. the growth rate
D. the dilution rate
E. A and B

22. During which phase of the growth curve might secondary metabolites (e.g., toxic compounds) be produced and growth occur without a net increase in the viable count?
A. lag
B. exponential
C. stationary
D. death
E. log

23. Penicillin inhibits _______
A. bacterial cell wall synthesis
B. bacterial protein synthesis
C. fungal cell wall synthesis
D. DNA replication
E. glycolysis

24. The decimal reduction time is ______.
A. the time required to kill all cells in a population at a given temperature
B. the time required to kill all cells in an autoclave
C. the time required to reduce the population of bacteria tenfold at a given temperature
D. the time required for a population to increase by tenfold
E. None of the above is correct.

25. Which of the following statements about DNA is incorrect?
A. DNA is composed of the four nucleotides adenine, guanine, cytosine, and thymine.
B. DNA is a double helix composed of two polynucleotides held together by hydrogen bonds.
C. The two polynucleotides have an antiparallel orientation.
D. The nucleotides are joined together by sulfhydryl bonds.
E. The polynucleotides have a sugar phosphate backbone.

26. According to the "Central dogma of molecular biology", information flows from ______.
A. RNA through DNA to protein.
B. protein through RNA to DNA
C. DNA through protein to RNA
D. DNA through RNA to protein
E. RNA through protein to DNA

27 The lac repressor protein regulates the lactose operon by ________.
A. repressing the activity of pre-existing enzymes
B. blocking transcription of protein from a mRNA
C. blocking DNA synthesis during transcription
D. blocking transcription of the operon by RNA polymerase
E. None of the above.

28. Enzymatic activity of a pathway (e.g., biosynthesis of an amino acid) can be controlled by the endproduct inhibiting the transcription of the genes involved in the synthesis of the amino acid. This is referred to as _________.
A. saturation
B. enzyme repression
C. positive control
D. substrate inhibition
E. feedback inhibition

29. Consider a mutation which occurs in which the change is from UAC to UAU, where both triplets code for the amino acid tyrosine. This is an example of a _____.
A. silent mutation
B. nonsense mutation
C. missense mutation
D. a point mutation
E. A and D

30. A mutant strain of E. coli that requires an amino acid for growth is called a ___.
A. caprotroph
B. lysogen
C. prototype
D. prototroph
E. auxotroph

31. Species of bacteria that spoil foods in a refrigerator are most likely _________.
A. mesophiles
B. barophiles
C. thermophiles
D. acidophiles
E. psychrophiles

32. Given a population of bacteria with an initial population of 5 x 10⁵ cfu/ml and a population of 1.28 x 10⁸ cfu/ml after 1 hour. How many generations has this culture gone through?
A. 1
B. 2
C. 4
D. 6
E. 8

33. Compounds that are structurally similar to required growth factors and inhibit the growth of microorganisms are called ______.
A. growth factor analogs
B. vitamins
C. coenzymes
D. cofactors
E. amino acids

34. True (A) or False(B): Antiseptics are chemical agents that inhibit or kill microorganisms and are sufficiently non-toxic to be used on living tissue.

35. ______ are the site of polypeptide synthesis. A. Ribozymes
B. RNA polymerases
C. Ribosomes
D. DNA polymerases
E. Nitrogenases

36. Which of the following is a characteristic of the lagging strand synthesis of DNA?
A. Continuous synthesis of the lagging strand towards the replication fork.
B. Synthesis of the lagging strand with an RNA template strand.
C. The lagging strand is synthesized by RNA polymerase.
D. Multiple RNA primers are needed for the lagging strand’s synthesis.
E. All of the above are characteristic of lagging strand synthesis.

37. True (A) or False (B): A tRNA can carry more than one type of amino acid to the growing polypeptide.

38. An operon where a regulator protein promotes the binding of RNA polymerase, thus increasing the amount of mRNA transcripts is ________.
A. negatively controlled
B. repressed
C. an example of attenuatio
D. positively controlled
E. catabolite repressed

39. A(n) _______ is a genetic element that is capable of moving from on segment of the chromosome to another and may code for antibiotic resistance genes.
A. plasmid
B. transposon
C. insertion element
D. mu
E. gamete

40. True (A) or False (B): An Hfr strain of E. coli mated with an F^-(minus) strain always results in the conversion of the F^-(minus) strain into an Hfr.

41. Which of the following species of phototrophic bacteria has two photosystems analogous to higher plants?
A. Green sulfur bacteria
B. sulfate reducing bacteria
C. Purple non sulfur bacteria
D. Purple sulfur bacteria
E. Cyanobacteria

42. Which of the following characteristics is common to both pseudomonads and Escherichia coli?
A. They both produce endospores.
B. They are both Gram negative rods.
C. They are both enteric bacteria.
D. They both are strict anaerobes.
E. All of the above are true about pseudomonads and Escherichia coli.

43. Which of the following characteristics unifies the phylogenetic group Crenarchaeota?
A. extreme halophiles
B. hyperthermophily
C. methanotrophy
D. chemolithotrophy
E. None of the above.

44. True (A) or False (B): Methane is generated by methanogens when they use carbon dioxide as a terminal electron acceptor in anaerobic respiration.

45. Which of the following human infectious diseases has been eradicated?
A. Smallpox
B. AIDS
C. Measles
D. Cholera
E. Flu

46. Which of the following statements about virus replication is false?
A. Virus replication involves de novo synthesis of viral proteins.
B. Viruses are obligate intracellular parasites.
C. Viruses reproduce by binary fission.
D. A and C
E. None of the above statements are false.

47. Which of the following are phototrophs?
A. algae
B. mushrooms
C. slime molds
D. protozoa
E. yeast

48. Which of the following statements about fungi is false?
A. They are heterotrophs.
B. Their cell wall is composed of chitin.
C. They do not have chlorophyll.
D. They do not contain a membrane bound nucleus.
E. They are decomposers.

49. The production of secondary metabolites occurs at or near the onset of which microbial growth phase?
A. Lag
B. Log
C. Exponential
D. Stationary
E. Death

50. Important industrial products produced by microorganisms include ____.
A. the cells themselves
B. primary metabolites
C. enzymes
D. secondary metabolites
E. all of the above.

51. A recognized resource book on prokaryote taxonomy is ________.
A. the American Type Culture Collection
B. Bergey’s Manual of Determinative Bacteriology
C. the American Society for Microbiology
D. your text book
E. none of the above

52. Nitrifiers carry out which of the following ecological functions in soils?
A. Reduction of ammonia to nitrate
B. Oxidation of methane to methanol
C. Reduction of sulfate to sulfide
D. Oxidation of ammonia to nitrate
E. Oxidation of hydrogen gas to protons

53. True (A) or False (B): Volcanic habitats have been the source of some of the most interesting hyperthermophiles, some of which grow at 100^oC.

54. Which of the following is not an adaptation of hyperthermophiles to high temperatures?
A. Synthesis of 2,3 diphosphoglycerate
B. Synthesis of DNA binding proteins
C. Modification in the primary sequence of polypeptides (e.g., proteins)
D. Synthesis of molecular chaperonins
E. All of the above are adaptations of hyperthermophiles to high temperatures.

55. During what stage of viral replication are the number of infectious virus particles (plaque-forming units) at their lowest?
A. latent period
B. penetration
C. maturation
D. release
E. attachment

56. True (A) or False (B): Viruses have been isolated from animals, plants, fungi but not bacteria.

57. Which type(s) of metabolism is/are found in the fungi?
A. photoautotrophy
B. chemolithotrophy
C. chemoorganotrophy
D. photoheterotrophy
E. A, C, and D

58. Which of the following protozoan groups may cause infectious disease in humans?
A. Mastigophora
B. Sarcodina
C. Ciliphora
D. Sporozoa
E. All of the above

59. Which of the following is(are) not a secondary metabolite?
A. antibiotics
B. ethanol
C. vitamins
D. amino acids
E. B, C, and D.

60. Which of the following fungi does not produce spores?
A. Deuteromycetes
B. Oomycetes
C. Zygomycetes
D. Basidiomycetes
E. Ascomycetes

61. Some pathogenic species of bacteria produce ____ to extract iron from iron carrying molecules like lactoferrin. A. transferrin
B. siderophores
C. fimbriae
D. hyaluronidase
E. streptokinase

62. True (A) or False (B): Tissue and host specific adherence is one of the initial interactions which leads to an infection of a host by a pathogen.

63. Which of the following causes lysis of redblood cells?
A. streptokinase
B. coagulase
C. hemolysin
D. collagenase
E. None of the above.

64. Endotoxins are usually associated with what type of microorganism?
A. Gram positive
B. Gram negative
C. protozoa
D. fungi
E. algae

65. Enterotoxin-producing strains of E. coli cause which of the following symptoms?
A. flaccid paralysis
B. systemic shock
C. diarrhea
D. rash
E. None of the above.

66. Which of the following is not a characteristic of an exotoxin?
A. heat labile (protein)
B. highly toxic
C. produces a fever
D. highly immunogenic
E. specific in their mode of action (e.g., neurotoxin)

67. True (A) or False (B): Only lysogenic strains of Corynebacterium diptheriae produce the diptheria exotoxin

68. Which of the following microorganisms may be a part of our normal skin microflora and is occassionally associated with food poisoning?
A. Clostridium perfringens
B. Vibrio cholerae
C. Pseudomonas aeruginosa
D. Staphylococcus aureus
E. Bacillus cereus

69. Which of the following is not an exotoxin?
A. the cholera toxin
B. the tetanus toxin
C. the diphtheria toxin
D. the LPS of Salmonella
E. the enterotoxins

70. True (A) or False (B): Clostridium tetani is a strict anaerobic soil organism that produces a neurotoxin that can lead to death.

71. A disease that is constantly present at a low incidence, in a population is called a(n) _________ disease.
A. pandemic
B. epidemic
C. endemic
D. pandia
E. pangeae

72. Which of the following are resevoirs of diseases?
A. animals
B. soil
C. water
D. man
E. All of the above.

73. True (A) or False (B): Typhoid Mary was an example of a chronic carrier of a disease. She may have been apparently healthy, but still harbored viable Salmonella typhi and spread it while she was a cook in various eating establishments.

74. Lyme disease is caused by Borrelia burgdorferi and is transmitted by infected ticks. This is an example of _______.
A. a sexually transmitted disease
B. a direct contact disease
C. a vector-borne disease
D. None of the above.

75. True (A) or False (B): A disease that primarily occurs in animals but can be transmitted to humans is referred to as a zoonosis.

76. Urinary tract infections caused by E. coli and P. aeruginosa may be acquired in hospitals. These are examples of _________.
A. fomites
B. nosocomial infections
C. vectors
D. zoonosis
E. None of the above.

77. True (A) or False (B): Hospital strains of Pseudomonas aeruginosa are frequently resistant to numerous antibiotics due to either plasmids or transposons.

78. ____ are inanimate objects, e.g., a toy, that transmit infectious agents between hosts.
A. Vectors
B. Carriers
C. Reservoirs
D. Fomites
E. Placebos

79. Which of the following is Not a factor in emerging diseases?
A. Human demographics and behavior
B. Technological advances, e.g., antibiotic usage.
C. Changes in land use patterns
D. Microbial evolution
E. All of the above are factors in the emergence of new diseases.

80. Cholera, a water-borne pathogen, has a ________disease pattern, where there is a sharp rise in the incidence of the disease and a relatively rapid decline.
A. host to host epidemic
B. common-source epidemic
C. vector-borne endemic
D. pandemic
E. None of the above.

Microbiology 2124
Exam 3
April 22, 1999
David Demezas

General Instructions: Fill in the requested information including your name, social security number, class (2124) and section number (001). Answer multiple choice questions on the scantron sheet. Answer other questions in the space provided on the test sheet. Be sure that you answer the question in complete sentences. Write your name on all pages of the test.
Multiple Choice (2 pts each). Choose the most correct answer and mark the corresponding letter on your scantron sheet.

D 1. Molecular phylogeny of bacteria is based on comparative analysis of _________ sequences.
A. ribosomes
B. 23s rRNA
C. RNA polymerase
D. 16S rRNA
E. DNA polymerase

E 2. Which of the following species of phototrophic bacteria has two photosystems analogous to higher plants?
A. Green sulfur bacteria
B. sulfate reducing bacteria
C. Purple non sulfur bacteria
D. Purple sulfur bacteria
E. Cyanobacteria

D 3. Which of the following is not true about anoxygenic photosynthesis?
A. It requires anaerobic conditions.
B. ATP is formed by cyclic photophosphorylation.
C. Bacteriochlorophyll is involved in the light reactions.
D. Water is oxidized to produce electrons and oxygen is released.
E. B and D

A 4. True (A) or False (B): Methane is produced by anaerobic methanogens and oxidized by aerobic methanotrophs.

A 5. ______ oxidize ammonia to nitrite and ________ oxidize nitrite to nitrate in soil.
A. Nitrosomonas / Nitrobacter
B. Bacillus / Nitrobacter
C. Pseudomonas / Nitrosomonas
D. Nitrobacter / Nitrosomonas
E. None of the above.

B 6. Which of the following compounds would be an unlikely energy source for chemolithotrophs?
A. NH₄⁺
B. SO₄^-2
C. Fe⁺²
D. H₂
E. All of the above.

B 7. Which of the following characteristics is common to both pseudomonads and Escherichia coli?
A. They both produce endospores.
B. They are both Gram negative rods.
C. They are both enteric bacteria.
D. They both are strict anaerobes.
E. All of the above are true about pseudomonads and Escherichia coli.

B 8. Which of the following is a species of nitrogen fixing bacteria?
A. Pseudomonas
B. Azotobacter
C. Proteus
D. Chromobacterium
E. Streptococcus

E 9. Which of the following is (are) potentially pathogenic to man?
A. Escherichia coli
B. Shigella
C. Salmonella
D. Proteus
E. All of the above.

A 10. True (A) or False (B): Strains of Bacillus thuringiensis have been used to control certain plant pests such as tent caterpillar and gypsy moth.

D 11. Which of the following is not an Archaea?
A. methanogens
B. extreme halophiles
C. extreme thermophiles
D. methanotrophs
E. Thermoplasma

C 12. Extreme halophilic archaea require between _____ salt for optimal growth.
A. 0 M
B. 0.5 M
C. 2 to 4 M
D. 10 M
E. 25 M

B 13. Which of the following characteristics unifies the phylogenetic group Crenarchaeota?
A. extreme halophiles
B. hyperthermophily
C. methanotrophy
D. chemolithotrophy
E. None of the above.

D 14. ______ use a membrane associated protein, bacteriorhodopsin, to generate a proton motive force to drive ATP synthesis.
A. Pseudomonads
B. Sulfate reducing bacteria
C. Methanogens
D. Halobacterium
E. Bacillus

A 15. True (A) or False (B): Methane is generated by methanogens when they use carbon dioxide as a terminal electron acceptor in anaerobic respiration.

A 16. True (A) or False (B): Elemental sulfur can be used as either an energy source or as a terminal electron acceptor in anaerobic respiration.

A 17. Hyperthermophiles produce large amounts of ______ as an adaptation to their extreme environment.

A. 2,3 diphosphoglycerate
B. water
C. glucose
D. pyruvate
E. citrate

18-20 Matching. Match the correct description with the genus of bacteria. Only one letter matches each species.

B 21. After a virus has attached and penetrated into a host cell, no virus can be detected until the host cell is lysed. This stage of viral replication cycle is called ________.
A. penetration
B. latent period
C. budding
D. lysis
E. attachment

A 22. Which of the following human infectious diseases has been eradicated?
A. Smallpox
B. AIDS
C. Measles
D. Cholera
E. Flu

C 23. Which of the following statements about virus replication is false?
A. Virus replication involves de novo synthesis of viral proteins.
B. Viruses are obligate intracellular parasites.
C. Viruses reproduce by binary fission.
D. A and C
E. None of the above statements are false.

A 24. Which of the following is the first virus identified?
A. Tobacco Mosaic Virus
B. Human Immunodeficiency virus
C. Herpesvirus
D. Smallpox virus
E. None of the above.

E 25. Viruses can be isolated from which of the following?
A. Animals
B. Plants
C. Fungi
D. Bacteria
E. All of the above.

A 26. True (A) or False (B) Bacteriophage lambda can insert its genome into the host bacterium's genome.

A 27. True (A) or False (B) The genetic material of a retrovirus is RNA.

A 28. True (A) or False (B) The genome of some viruses consists of single stranded DNA.

A 29. True (A) or False (B) Some viruses can cause cancer.

B 30. True (A) or False (B) Viruses are larger than bacteria.

A 31. Which of the following are phototrophs?
A. algae
B. mushrooms
C. slime molds
D. protozoa
E. yeast

C 32. Crushed cell walls of diatoms (diatomaceous earth) is used to control plant pests. The cell wall is composed of ________.
A. cellulose
B. chitin
C. silica
D. xylans
E. nucleic acids

D 33. Which of the following statements about fungi is false?
A. They are heterotrophs.
B. Their cell wall is composed of chitin.
C. They do not have chlorophyll.
D. They do not contain a membrane bound nucleus.
E. They are decomposers.

B 34. Mushrooms are classified as __________.
A. Ascomycetes
B. Basidiomycetes
C. Zygomycetes
D. Oomycetes
E. Deuteromycetes

C 35. The usual mode for protozoa and slime molds to obtain food is by _____.
A. autotrophy
B. osmosis
C. phagocytosis
D. lithotrophy
E. None of the above

D 36. Which of the following groups of organisms are unicellular and lack a cell wall?
A. Fungi
B. Molds
C. Yeast
D. Protozoa
E. None of the above.

A 37. Which of the following protozoan groups causes African sleeping sickness in humans?
A. Mastigophora
B. Sarcodina
C. Ciliphora
D. Sporozoa
E. All of the above

C 38. Which of the following is an asexual spore?
A. basidiospore
B. ascospore
C. conidia
D. oospore
E. zygospore

B 39. True (A) or False (B): Sporozoa form spores as its name implies!

B 40. True (A) or False (B): All protozoa are obligate aerobes.

D 41. Which of the following characteristics would not be important for a microorganism used in an industrial process?
A. Fast growth rate
B. Genetically stable
C. Amenable to genetic manipulations
D. Must be a prokaryote
E. Must not be a plant or animal pathogen

D 42. The production of secondary metabolites occurs at or near the onset of which microbial growth phase?
A. Lag
B. Log
C. Exponential
D. Stationary
E. Death

B 43. True (A) or False (B): Secondary metabolites are essential for growth of the microorganism producing it.

C 44. Which of the following microbial products is not a primary metabolite?
A. vitamin B12
B. riboflavin
C. antibiotics
D. ethanol
E. amino acids

E 45. Important industrial products produced by microorganisms include ____.
A. the cells themselves
B. primary metabolites
C. enzymes
D. secondary metabolites
E. all of the above.

C 46. Commercial production of amino acids relies upon which of the following techniques for increasing yield of the product?
A. Obtaining mutants not subjected to feedback inhibition
B. Obtaining mutants insensitive to repression.
C. A and B
D. none of the above.

B 47. True (A) or False (B): All antibiotics are produced by fungi.

A 48. True (A) or False (B): Bioconversion is a process of transforming or modifying a chemical using bacteria to carry out the transformation.

B 49. True (A) or False (B): Viruses have no place in industrial microbiology.

B 50. Vitamin B12 is made exclusively by microorganisms. Commercially B12 is synthesized by _________.
A. Bacillus species
B. Propionibacterium species
C. Streptomyces species
D. Ashbya species
E. Rhizopus species

51. (10 pts) The 16s ribosomal RNA gene has been called a "mosaic of domains". Name and describe the three domains of the 16s rRNA gene discussed in class.
The 16s rRNA gene is composed of three domains; they are highly conserved, semi-conserved and hyper-variable domains. These domains are distributed throughout the gene. Comparison of 16s rRNA genes from many different species of bacteria revealed these domains. The highly conserved domains show very little differences between all of the compared sequences of eubacteria (Bacteria). The semiconserved sequences show some variability but are conserved among members of the same phylogenetic groups such as methanogens. The hypervariable domains show a low degree of similarity between different species examined.

52. (10 pts) Life exists at temperatures that normally denature DNA and proteins. What types of adaptations have bacteria evolved that protect (a) DNA and (b) proteins and allow extreme thermophiles to live at temperatures approaching 100oC?
DNA and proteins are denatured by high temperatures. Extreme thermophiles have evolved a number of different adaptations to these high temperatures. To protect the DNA, DNA binding proteins, which bind to DNA, are synthesized. A specific solute, 2,3-diphosphoglycerate, is produced in large amounts. This compound helps both DNA and proteins from being denatured by high temperatures. Proteins have primary structures that lead to increased stability of the secondary, tertiary and quatenary structures of proteins. Also small proteins called chaperonins are synthesized to help protect proteins.

General Instructions: Answer multiple choice questions on the test sheet. Answer other questions in the space provided on the test sheet. Be sure that you answer the question in complete sentences. Write your name on all pages of the test.
Multiple Choice (2 pts each). Choose the most correct answer and mark the corresponding letter on the blank provided to the left of the question.

E 1. The time required for the formation of two cells from one cell is called _____.
A. the generation time
B. the doubling time
C. the growth rate
D. the dilution rate
E. A and B

D 2. Given a population of bacteria with an initial population of 5 x 10⁷ cfu/ml and a population of 8 x 10⁸ cfu/ml after 1 hour. What is the doubling time of this culture?
A. 0.5 hours
B. 1 hour
C. 2 hours
D. 0.25 hours
E. 4 hours

E 3. Bacterial populations increase in size by _________.
A. meiosis
B. mitosis
C. fusion
D. replication
E. binary fission

B 4. Hydrogen peroxide is a potentially toxic compound generated during aerobic respiration. Which of the following enzymes degrades hydrogen peroxide to water and oxygen?
A. super oxide dismutase
B. catalase
C. hydrogenase
D. nitrogenase
E. oxidase

C 5. During which phase of the growth curve might secondary metabolites (e.g., toxic compounds) be produced and growth occur without a net increase in the viable count?
A. lag
B. exponential
C. stationary
D. death
E. log

A 6. True (A) or False (B). In a chemostat, the population density is controlled by the nutrient concentration and the growth rate is controlled by the dilution rate.

D 7. Which of the following methods for assaying microbial growth in broth culture is simplest and most convenient?
A. microscopic counts
B. plate counts
C. cell nitrogen
D. turbidity
E. oxygen uptake

B 8. The temperature of the interior portion of a "hot" compost pile might be 65 to 70 ^oC. What type of bacteria grows at these temperatures?
A. psychrophile
B. thermophile
C. mesophile
D. extreme thermophile
E. psychrotroph

C 9. Dried fruit with a water activity (aw) = 0.7 might be spoiled (colonized) by which of the following?
A. halophile
B. osmophile
C. xerophile
D. psychrophile
E. None of the above.

E 10. Which of the following types of bacteria require oxygen for growth?
A. aerobes
B. facultative anaerobes
C. microaerophiles
D. anaerobes
E. a and c

B 11. True (A) or False (B). Dry heat is more effective at killing bacteria than moist heat.

D 12. Which of the following are the correct parameters for an autoclave to sterilize a small amount (1 liter) of medium?
A. 121^oC at atmospheric pressure for 15 minutes
B. 212 ^oC at atmospheric pressure for 10 minutes
C. 100 ^oC at 100 lbs/sq inch for 5 minutes
D. 121 ^oC at 15 lbs/sq inch for 15 minutes
E. None of the above are correct.

B 13. True (A) or False (B). A bactericidal agent only inhibits the growth of bacteria.

E 14. Which of the following would be the most appropriate means to sterilize heat labile vitamins?
A. autoclaving
B. filter sterilizing
C. boiling
D. UV irradiation
E. B and D

A 15. Which of the following classes of antibiotics does not inhibit protein synthesis?
A. [beta]-lactams
B. aminoglycosides
C. macrolides
D. tetracycline
E. All of the above inhibit protein synthesis.

B 16. True (A) or False (B). Bacteriological medium can be sterilized by autoclaving for less than 15 minutes without regard to the volume of medium being sterilized.

B 17. Which of the following is best suited for reducing spoilage of fresh meat prior to shipment?
A. boiling
B. irradiation
C. phenol treatment
D. autoclaving
E. All of the above.

A 18. Penicillin inhibits _______
A. bacterial cell wall synthesis
B. bacterial protein synthesis
C. fungal cell wall synthesis
D. DNA replication
E. glycolysis

C 19. The decimal reduction time is ______.
A. the time required to kill all cells in a population at a given temperature
B. the time required to kill all cells in an autoclave
C. the time required to reduce the population of bacteria tenfold at a given temperature
D. the time required for a population to increase by tenfold
E. None of the above is correct.

A 20. True (A) or False (B). Ionizing radiation sterilizes materials by producing highly reactive hydroxyl radicals that react with and damage DNA and other macromolecules.

D 21. Which of the following statements about DNA is incorrect?
A. DNA is composed of the four nucleotides adenine, guanine, cytosine, and thymine.
B. DNA is a double helix composed of two polynucleotides held together by hydrogen bonds.
C. The two polynucleotides have an antiparallel orientation.
D. The nucleotides are joined together by sulfhydryl bonds.
E. The polynucleotides have a sugar phosphate backbone.

D 22. According to the "Central dogma of molecular biology", information flows from ______.
A. RNA through DNA to protein.
B. protein through RNA to DNA
C. DNA through protein to RNA
D. DNA through RNA to protein
E. RNA through protein to DNA

A 23. The ratio of guanine to cytosine nucleotides in cellular DNA is ____.
A. 1:1
B. 2:1
C. 4:1
D varies with the species of bacteria
E. None of the above.

D 24. _____ catalyzes the reaction between the incoming deoxynucleotide and the growing end of DNA and proofreads each inserted nucleotide.
A. DNA helicase
B. DNA gyrase
C. DNA polymerase I
D. DNA polymerase III
E. DNA ligase

B 25. True (A) or False (B) - Incoming nucleotides are added to the 5-prime phosphate group of the growing polynucleotide during DNA replication.

B 26. Which of the following statements about RNA is incorrect?
A. RNA acts at both the genetic and functional levels.
B. The sole difference between DNA and RNA is that ribose, rather than 2- deoxyribose, is present only in DNA.
C. RNA is the product of transcription carried out by RNA polymerase.
D. Only mRNA is translated into a polypeptide.
E. tRNA are the smallest RNA molecules.

B 27. True (A) or False (B). Okazaki fragments are synthesized towards the replication fork on the leading strand.

D 28. The minimum number of nucleotides on a strand of DNA required to code for a polypeptide consisting of 150 amino acids would be ____.
A. 50
B. 150
C. 300
D. 450
E. 600

A 29. True (A) or False (B). More than one codon may code for a specific amino acid, but no codon may code for more than one amino acid.

A 30. If the anticodon of a tRNA carrying serine is AGU then the codon in the mRNA is ____ and the corresponding DNA sequence is ______.
A. UCA / AGT
B. AGU / UCA
C. UCA / UCA
D. AGU / AGU
E. ACU / TGA

B 31. A major mechanism for the control of enzyme activity involving regulation of pre-existing enzymes is _____.
A. operon control
B. feedback inhibition
C. global control
D. sigma replacement
E. all of the above.

B 32. Enzymatic activity of a pathway (e.g., biosynthesis of an amino acid) can be controlled by the endproduct inhibiting the transcription of the genes involved in the synthesis of the amino acid. This is referred to as _________.
A. saturation
B. enzyme repression
C. positive control
D. substrate inhibition
E. feedback inhibition

D 33. The repressor protein regulates the lactose operon by ________.
A. repressing the activity of pre-existing enzymes
B. blocking transcription of protein from a mRNA
C. blocking DNA synthesis during transcription
D. blocking transcription of the operon by RNA polymerase
E. None of the above.

B 34. Enzymes whose level of synthesis is constant under all growth conditions are called _____.
A. allosteric enzymes
B. constitutive enzymes
C. global enzymes
D. positively regulated enzymes
E. negatively regulated enzymes

B 35. The repression of the lactose operon by the presence of glucose is mediated through ________.
A. elevated level of cyclic AMP in the cell
B. depressed levels of cyclic AMP (cAMP) in the cell
C. a lac repressor /glucose complex binding to the lac operator
D. glucose binding to the lac operator
E. None of the above.

D 36. Unrelated genes required for the survival of carbon starvation are scattered throughout the chromosome of Escherichia coli and are under control of the same global regulatory protein. These genes are part of a(n) _____.
A. operon
B. regulon
C. exon
D. modulon (syn. stimulon)
E. none of the above

E 37. Which of the following statements is False about cells in the early part of the second phase of diauxic growth in a glucose/lactose based medium?
A. The lac repressor is bound to the inducer and cannot bind to the operator region.
B. The levels of cyclic AMP are elevated relative to the first phase of growth.
C. The lac operon is induced.
D. cAMP/CAP is bound to the CAP binding site.
E. All of the above statements are true.

E 38. Repression of the lac operon by glucose is referred to as __________.
A. catabolite repression
B. catabolite activation
C. derepression
D. glucose effect
E. A and D

B 39. True (A) or False (B). The above figure illustrates diauxic growth.

A 40. True (A) or False (B). Different sigma factors may act as global regulators of gene expression.

E 41. A mutant strain of Escherichia coli that requires an amino acid for growth is called a ___.
A. autotroph
B. lysogen
C. prototype
D. prototroph
E. auxotroph

A 42. A mutation has occurred which is readily reversible to restore the original parental phenotype. This mutation is most likely due to a ______.
A. base-pair substitution
B. microdeletion
C. microinsertion
D. pyrimidine dimer
E. None of the above.

E 43. Consider a mutation which occurs in which the change is from UAC to UAU, where both triplets code for the amino acid tyrosine. This is an example of a _____.
A. silent mutation
B. nonsense mutation
C. missense mutation
D. a point mutation
E. A and D

B 44. True (A) or False (B). Ultraviolet light is a form of ionizing radiation that produce radicals that react with macromolecules such as DNA.

B 45. _______ are cells capable of taking up DNA from the environment.
A. Conjugative cells
B. Competent cells
C. Transducing cells
D. Hela cells
E. Minicells

E 46. Plasmids may code for all of the following functions except ____.
A. antibiotic resistance
B. toxins
C. bacteriocins
D. catabolic pathways
E. All of the above are coded for by plasmids

A 47. True (A) or False (B). Only the donor cell (F⁺) make sex pili for conjugation.

48-50. Match each term with the appropriate statement (A-E) about it.

The following questions are each worth 10 pts. Write or draw your answers on the sheet of paper provided.
51. Consider an inducible operon such as lac operon and a repressible operon such as arginine operon.
A. Draw the state of each operon when the respective inducer and co-repressor is present in excess amounts in the cell. Be sure to label the promoter, operator, structural genes, repressor, and corepressor (or inducer)

Lactose is present - lactose binds to repressor and the lac/repressor does not bind to the operator and transcription occurs.

Agrinine is present and it binds to the repressor which now binds to the operator and blocks transcription.

B. Draw the state of each operon when the respective inducer and co-repressor is absent from the cell. Be sure to label the same elements listed above where appropriate.

Lactose absent - repressor binds to operator and transcription is blocked

Arginine absent and the repressor does not bind to the operator and transcription occurs.

52. Identify or define each of the following terms:

F⁺ cell - male, F plasmid-donor cell

F ^- cell - female, plasmid-recipient cell

Hfr cell - male, F plasmid integrated into chromosome

F-prime - male, F plasmid integrated and excised from chromosome. F plasmid contains a bit of chromosome.