Question

34) During Salmonella enterica gastroenteritis (acute inflammation of the stomach and intestines, often accompanied by nausea, vomiting, diarrhea, and abdominal pain), responding neutrophils of the human immune system generate an oxidizing environment that generates tetrathionate, a compound Salmonella uses as a terminal electron acceptor for anaerobic respiration. Most normal microbiota are unable to use this compound, instead relying on fermentation in this anaerobic environment. In the densely populated intestinal tract, this . A) slows the growth of Salmonella relative to the normal microbiota, helping to contain the infection B) allows Salmonella to oxidize organic compounds the other species are unable to oxidize C) gives Salmonella a competitive advantage due to the higher energy yield of anaerobic respiration vs. fermentation D) inhibits Salmonella growth by forcing it to respire anaerobically instead of aerobically

35) You discover a species of bacteria that grows photoautotrophically, with inputs of light, hydrogen sulfide (H2S), and CO2 and outputs of cell biomass and sulfur. Upon sequencing its genome, you find it has genes for the TCA cycle but not the Calvin cycle. This species is most likely A) obtaining electrons from H2S and fixing CO2 via a reverse TCA cycle B) obtaining electrons from CO2 and fixing CO2 via glycolysis and the TCA cycle C) obtaining electrons from sunlight and fixing CO2 via a reverse TCA cycle D) obtaining electrons from CO2 and fixing H2S via a reverse TCA cycle

36) The methylotrophic bacterium Paracoccus denitrificans oxidizes the organic single-carbon compound methanol (CH3OH) all the way to carbon dioxide in order to generate ATP using an electron transport chain, and then fixes this carbon dioxide via the Calvin cycle. Under these conditions, this means P. denitrificans is a A) chemoorganoheterotroph B) chemolithoheterotroph C) chemoorganoautotroph D) chemolithoautotroph

37) Following from the previous question, when Paracoccus denitrificans is growing as a methylotroph using methanol for its energy and carbon needs, it is able to grow anaerobically by reducing nitrate to nitrite. This means under these conditions that P. denitrificans is growing using A) aerobic respiration B) autotrophy C) anaerobic respiration D) fermentation

38)You have the following consumable items that you do not want spoiled by the action of microorganisms, but you have space in your refrigerator for only one. You have already opened each and consumed some. Which one of these is most likely to spoil fastest and should therefore be placed in the fridge?

1. Bread
2. Flavored syrup (contains water, high sugar concentration, flavors, e.g., used to flavor coffee and drinks)
3. Apple juice
4. 80 proof liquor (contains water, 40% ethanol, flavors)
5. Mineral water (contains water, minerals)

Answer 1