BIOL 455 GENERAL MICROBIOLOGY Second Lecture Exam SPRING 2002 EXAM VERSION #1 EXAM VERSION #1 EXAM VERSION #1

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1 BIOL 455 GENERAL MICROBIOLOGY Second Lecture Exam SPRING 2002 EXAM VERSION #1 EXAM VERSION #1 EXAM VERSION #1 CORRECTLY MARK YOUR STUDENT NUMBER and EXAM VERSION ON THE ANSWER CARD! MARK THE APPROPRIATE CIRCLE ON THE ANSWER CARD TO HAVE YOUR GRADE POSTED. PLEASE CHECK YOUR POSTED SCORE FOR ACCURACY!!!!! YOU MAY KEEP THE EXAM QUESTIONS. In the MULTIPLE CHOICE questions below, a numbered statement will be followed by four items lettered a), b), c) or d). Only one letter should be marked per question, and you are to answer by marking the correspondingly lettered circle on the computer card. Occasionally item d) may be "more correct" and should therefore be the single item marked. Each correct answer in this section is worth 3 points. 1. With respect to environmental influences, microorganisms; a) generally are immune to influences of ph and temperature. b) might be obligately aerobic, yet be unable to tolerate the levels of oxygen normally found in air. c) must have lysozyme available from the environment to allow cutting of β(1-4) bonds to permit insertion of peptidoglycan precursors into the growing peptidoglycan girdle. d) none of the above. 2. The peptidoglycan (murein) precursor of a Gram (+) bacterium; a) is compositionally identical to the peptidoglycan precursor found in Gram (-) bacteria. b) has one more amino acid in its amino acid side chain than does the side chains of already synthesized peptidoglycan. c) is not synthesized in the presence of the antibiotic penicillin.

2 3. The autolytic enzyme; a) is responsible for cleaving one of two D-Alanines from a newly inserted precursor side chain followed by crosslinking the remaining D-Alanine to a diamino acid on an adjacent side chain. b) is identical in function to the carboxylase enzyme. c) cuts and reforms two β(1-4) bonds per peptidoglycan precursor inserted. d) all of the above. 4. Protoplasts and spheroplasts; a) are produced from Gram (+) and Gram (-) cells respectively. b) may re-grow a murein girdle if a spheroplast, but not if a protoplast. c) must be osmotically protected to exist. d) all of the above. 5. Bacterial cells with a doubling time of 35 minutes; a) have a C period that is 2/3 as long as the doubling time. b) spend a total of 95 minutes completing I, C, and D. c) seemingly cannot support more than one set of bi-directional replication forks per chromosome. 6. The cell envelope; a) is a term describing the outer membrane, the R-layer, and the cell membrane. b) is of similar structure in Gram (+) and Gram (-) bacteria. c) contains an outer membrane that consists of phospholipids, lipopolysaccharide, lipoprotein, diffusion and structural proteins, permeases, and group translocation proteins. 7. Given that peptidoglycan components are roughly the same in all bacteria [of course differ Gram (+) and Gram (-) in one amino acid], the differences in morphology seen in the 5 common shapes of bacteria is a function of peptidoglycan; a) composition. b) structural components. c) arrangement. d) none of the above. 8. Gram (-) peptidoglycan; a) is crossed-linked within only two planes. b) is the most recognizable eternal feature of the cell. c) is ionically linked to the outer membrane.

3 9. Water activity; a) will have a value of less than 1.0. b) is equal to the vapor pressure of the solvent (water) divided by the vapor pressure of the solution. c) values which one encounters under normal food processing conditions are likely to be above Lipoprotein; a) is found on the outside surface of the outer membrane in Gram (-) bacteria. b) is a two-part molecule, one end of which is lipid and the other end of which is a protein which can form a peptide bond with diamono-pimelic acid in the R-layer. c) carries (and holds in proper position for eventual insertion) the peptidoglycan precursor. 11. ATP-mediated transport as it occurs in bacteria; a) is the mechanism whereby bacteria move molecules larger than water across the cell (inner or cytoplasmic) membrane. b) allows the importation of specific molecules against a concentration gradient. c) is accomplished by permeases or the group translocation system d) all of the above. 12. Antibiotics can be successfully used to treat a wide variety of human infections; a) because the bacterial cell membrane is completely permeable to molecules larger than the water molecule. b) because antibiotics tend to affect chemical reactions or anatomical features which are unique to procaryotic cells. c) because microorganisms which cause infections cannot mutate to become antibiotic resistant. d) all of the above. 13. The nucleus (nucleoid) of an exponentially growing Escherichia coli bacterial cell displaying a doubling time of 150 minutes; a) contains a covalently closed, double stranded DNA molecule about 1000 µm in length and which is attached to the cell membrane at the replication origin, the replication terminus, and at the replication forks. b) exists in the cell in multiple copies because the C period of the cell cycle is longer than the I period. c) is replicated at the same rate (in the same amount of time) as it would be if the cells were dividing with a 40 minute doubling time. d) none of the above.

4 In the MULTIPLE CHOICE questions below, a numbered statement will be followed by FIVE items lettered a), b), c), d) or e). Only one letter should be marked per question, and you are to answer by marking the correspondingly lettered circle on the computer card. Occasionally item e) may be "more correct" and should therefore be the single item marked. Each correct answer in this section is worth 3 points. 14. Chromosome replication in bacterial cells; a) is interrupted by DNA replication gaps when doubling times are 120 minutes or more. b) is accomplished by movement of two replication complexes (replication forks) moving in opposite directions until they collide thereby indicating that the chromosome is complete. c) begins at a frequency equal to the doubling time at all known growth rates. d) requires a synthesis time which is designated as the I period. e) two of the above. 15. Metabolism of Microorganisms: a) Photoautotrophs obtain the carbons needed for anabolism from organic compounds. b) Chemoheterotrophs are the microorganisms that are most often used in lab. c) Like most bacteria, humans are chemoautotrophs. d) Photoheterotrophs are organisms that use photosynthesis to provide energy and obtain carbon from carbon dioxide. e) three of the above. 16. A single bacterial species grown under different conditions will often produce very different growth rates and/or amounts of cell biomass. Reasons why this is true include; a) the fact that organisms may be using fermentation under some conditions and respiration under others. b) the fact that obligate aerobes may be growing without available oxygen. c) the fact that oblivious facultative anaerobes respond differently to the presence of oxygen. d) the fact that organisms may have different metabolic intermediates available in the particular media displaying the response. e) two of the above.

5 17. Presume you have a psychrophilic Gram (+) microorganism which has a minimum growth temperature of 5 C, a maximum growth temperature of 18 C and an optimum growth temperature of 15 C. The organism is also an "oblivious" facultative anaerobe. Which of the following would be true of such an organism? a) The length of the I period will be less at 5 C than at 15 C. b) The cells would likely have more unsaturated fatty acids in their cytoplasmic membranes than would a thermophile. c) The microorganism will use respiration to generate energy if grown aerobically and fermentation to generate energy if grown anaerobically. d) The organism will have 2-D peptidoglycan. e) Two of the above. 18. The cytoplasmic membrane of a typical Gram (-) bacterium; a) appears to be connected to the outer membrane via bridging structures called Beyer's patches.. b) is the location of mesosomes. c) potentially contains all membrane associated molecules and functions which might be found within the organelles of eucaryotic cells. d) is the location of porins (matrix proteins). e) three of the above. 19. For a Gram (-) bacterium to move molecules such as carbon sources and biosynthetic precursors from the cell's environment into the cell's cytoplasm; a) the cell must be in an environment with a high enough water activity to allow cell survival. b) porins (matrix proteins) specific for the molecule(s) must be present in the outer membrane. c) specific permeases or group-translocation system(s) must be present in the inner membrane. d) a, b, and c above. e) none of the above. 20. Assume the inoculation and incubation of agar tubes that had been autoclaved and cooled such that only the top 1 centimeter or so of the medium contained measurable oxygen. In tube #1 growth was absent on the agar surface, present in a narrow zone within the oxygen-containing area but absent in the oxygen-free area, and in tube #2 growth was uniform but light in all regions of the tube. The means of energy generation and oxygen-response classification of the organism in each tube would be; a) #1; respiration, obligate aerobe---#2; fermentation, obligate anaerobe. b) #1; respiration, microaerophile---#2; fermentation, +/- facultative anaerobe. c) #1; respiration, microaerophile---#2; fermentation, oblivious facultative anaerobe. d) #1; respiration, obligate anaerobe---#2; respiration, oblivious facultative anaerobe. e) #1; fermentation, +/- facultative anaerobe---#2; fermentation, oblivious facultative anaerobe.

6 21. Procaryotic microorganisms: a) Use 70S ribosomes to translate mrna messages into protein. b) include the only examples of the nutritional category called chemoautotroph. c) are essentially identical to eucaryotes in their susceptibility to antibiotics. d) may contain 3-D peptidoglycan, but only if they are Gram (+). e) three of the above. 22. Catabolism and anabolism in microorganisms; a) are energy yielding metabolic processes which use organic compounds and light as energy sources respectively. b) since they occur within mesosomes are actually occurring outside the cytoplasm. c) are carried out by pathways which are generally oxidative (catabolism) and reductive (anabolism). d) are called fermentation and respiration respectively. e) two of the above. 23. Mesosomes; a) is/are the name that "eucaryote biologists" give to the DNA in the procaryotic cell's nucleoid. b) are sock-like invaginations of the inner or cytoplasmic membrane. c) are thought to be involved with septum invagination in procaryotes. d) are the covalent connections between the outer membranes and the R- layer in Gram (-) bacteria. e) two of the above. 24. Fermentation pathways; a) all produce lactic acid as a fermentation end product. b) produce hydrogen peroxide as a normal end product. c) produce ATP via substrate-level phosphorylation. d) typically oxidize organic compounds [CH 2 O] completely to CO 2. e) three of the above. In the following TRUE/FALSE statements, mark circle "A" if the statement is true, and mark circle number "B" if the statement is false. Each correct answer in this section is worth 2 points. 25. T(A) F(B) Normal Gram (-) or Gram (+) bacterial cells which are placed into high salt (or high amounts of some other solute) undergo dehydration and become structures called spheroplasts.

7 26. T(A) F(B) Insertion of the peptidoglycan precursor into an existing peptidoglycan girdle uses three enzymes which are able to catalyze their respective reactions because any energy they need is provided i) through cutting bonds in the existing peptidoglycan, ii) via cutting the bond connecting the precursor to the C 55 carrier molecule or iii), through cutting bonds present within side chains of the precursor itself. 27. T(A) F(B) The periplasmic space is the space between the cell membrane and the cell wall in protoplasts. 28. T(A) F(B) Permeases are proteins which have high affinity for given substrates and "hold" the substrates until they can be chemically modified (at the expense of ATP) after which affinity between pearmease and modified substrate is lost. 29. T(A) F(B) A medium with a water activity in the range of 0.7 to 0.8 may cause a microorganism which finds itself in that medium to undergo plasmolysis. 30. T(A) F(B) In the Embden-Meyerhof pathway of fermentation, 2 ATPs are added to the glucose molecule and 4 ATPs are eventually produced from the two C 3 intermediates, yielding a net of 2 ATPs/glucose; however, for a microorganism to truly realize 2 ATPs/glucose it must use a group translocation protein rather than a permease to transport the glucose into the cell. 31. T(A) F(B) Since a +/- facultative anaerobe has within its genetic code the information for the enzyme pathway(s) of both fermentation and respiration, both of the catabolic processes will be used regardless of whether or not oxygen is available. 32. T(A) F(B) Lysozyme is an enzyme produced by eucaryotic organisms and is used by them as a defense against prokaryotes. 33. T(A) F(B) The acetone-butanol fermentation is in part responsible for the current Israeli-Palestinian political situation. 34. T(A) F(B) In Gram (-) bacteria, ATP-mediated transport is required to move specific molecules across both the outer and inner membranes. 35. T(A) F(B) Fermentation apparently cannot occur in the presence of air (oxygen).

8 36. T(A) F(B) Obligate anaerobes are killed by exposure to oxygen because i) the intracellular redox potentials necessary for cellular enzymes to be functional cannot be maintained, ii) they "accidently" produce hydrogen peroxide from which they have no protection, and/or iii) they produce no superoxide dismutase. 37. T(A) F(B) A bacterial cell in the D period of the cell cycle appears to use a different set of peptidoglycan enlargement enzymes than it does in other phases of the cell cycle. 38. T(A) F(B) Lipopolysaccharide is found on the outer surface of the outer membrane of the Gram (-) cell envelope and when liberated into the human bloodstream induces fever and symptoms of shock. The end, the end, the end. ANSWERS::::::::1-b; 2-b; 3-c; 4-d; 5-b; 6-a; 7-c; 8-a; 9-d(ac); 10-b; 11-d; 12-b; 13-a; 14-e(ac); 15-b; 16-e(ad); 17-b; 18-e(abc); 19-d; 20-c; 21-e(abd); 22-c; 23-e(bc); 24-c; 25-b; 26-a; 27-b; 28-b; 29-a; 30-a; 31-b; 32-a; 33-a; 34-b; 35-b; 36-a; 37-a; 38-a.