MICROBIOLOGY TEST 1 - SPRING 2007

Transcription

1 MICROBIOLOGY TEST 1 - SPRING 2007 Name Part One: Short Answers. Answer 5 of the following 6 questions in the space that has been provided. Each question is worth 15 points. Question 1: Name and briefly describe 3 molecular adaptations that are present in psychrophilic or thermophilic prokaryotes using as a guide the fictitious answer in row 1. Indicate in column 2-3 if the adaptations are present in psycrophiles (P), thermophiles (T), and if they are present in Archaea (A), Bacteria (B) or both (A,B) Adaptation Name/Function In psychrophiles or thermophiles? Archaea or Bacteria? Thick, purple membranes made of cheese / Membranes thicken in response to cold and protect the cell P A,B 1

2 Question 2: Briefly compare the biosynthetic and bioenergetic roles of the citric acid cycle in heterotrophs with its roles in autotrophs. In each case, tell where the microbe originally gets its carbon, energy and electrons. Question 3: We have studied many types of motility this semester. Briefly discuss three ways in which microbes move in response to changes in their environments, using at least one example from the book and one example from the outside readings. Make sure to name the structure(s) used in each form of motility (you do not need to give detailed molecular structures - just the name), and to tell exactly how the structure controls or augments motility. 2

3 Question 4: Microbes display remarkable metabolic diversity and flexibility. Briefly differentiate between anaerobic, facultative anaerobic, phototrophic and facultative phototrophic bacteria, and describe under what environmental conditions a microbe might utilize each metabolic strategy. Question 5: All of our probiotic bacteria use fermentation as a metabolic strategy. Why is fermentation a necessary alternative to respiration in many cells? Why do you think all (or at least most) of the probiotic bacteria currently being developed by industry use fermentation (give two specific reasons)? 3

4 Question 6: Most antibacterial drugs disrupt or destroy prokaryotic cellular characteristics that are different from those of eukaryotic cells, or which may not even be present in eukaryotic cells. List and describe at least three prokaryotic cellular features that could be targeted in this way to inhibit or kill a bacterial pathogen. 4

5 Essays: Answer 1 of the following 3 essays (25 points). If you choose essays A or B, answer on the front and back of this sheet. If you choose essay C, which can be found on the next sheet, answer that question on its own page. Please clearly indicate the letter of the essay that you have answered. Essay A: Microbial Fueling. Microbial growth metabolism generally requires the establishment of a transmembrane ion gradient. Describe four ways in which such a gradient can be established, and three specific ways in which these gradients are used by the microbe once they are established. Make sure that the latter examples directly (rather than indirectly) utilize the ion gradient. Describe how the establishment of ion gradients can impact the local environment. Essay B: Microbial Growth. You have been placed in charge of developing the perfect industrial large-scale culture conditions for the growth of a microbe that produces a new antimicrobial peptide called BactEraser. Write a brief memo to the company s stockholders that discusses how the physiology of a microbe is impacted by its growth rate, and how changes in microbial growth rate can be expected to impact the microbe s production of BactEraser. Next, discuss the types of culture conditions that you plan to vary to maximize your microbe s growth rate and how you will use a chemostat to keep your microbe in balanced growth once you have discovered those conditions. Since maintaining balanced growth is expensive, be sure to tell your stockholders why it is important. 5

6 Essay C: Microbial Biosynthesis. Using the metabolic pathway below, tunnel your way in to the fundamental molecules involved in nitrogen assimilation by first circling each of the 13 precursor metabolites that are used for biosynthetic pathways, then by indicating with an asterisk (*) which of the precursor metabolites give rise to the 6 amino acid families and finally by indicating with an N which metabolites give rise to the central molecules in nitrogen assimilation. Name those two molecules. Finally, describe the formsm in which nitrogen can enter microbial cells, and the global impacts of these processes. 6