41) In the absence of oxygen, E. coli induces expression of the enzyme nitrate r

Question

41) In the absence of oxygen, E. coli induces expression of the enzyme nitrate reductase for anaerobic respiration which converts: a. NO3NO2 d. NOamino acids 42) Which of the following is TRUE regarding the Euprymna-Alivibrio (squid-bacterium) symbiosis: a. Animal host receives nutrition in the form of sugars from the bacteria b. Bacterial partner passes reduced carbon from CO2 fixation to the animal host c. Bacterial partner receives nutrients from the host animal d. Symbionts fix nitrogen which is passed to the host animal e. This symbiosis is non-specific since several species of marine bacteria can serve as symbionts 43) Which region of the human gastrointestinal tract harbors the greatest diversity of microorganisms? a. Esophagus b. Large intestine c. Stomach d. Rumen e. All of the above have similar microbial diversity 44) A cow's main source of energy is: a. The oxidation of volatile fatty acids produced by microbes in the stomach b. The oxidation of volatile fatty acids produced by microbes in the rumen c. CO2 fixation by microbes in the rumen d. The oxidation of methane produced by microbes in the rumern e. The direct digestion of microbes in the rumern

Explanation / Answer

1) Anaerobic respiration is an alternate mode of energy generation in which an exogenous electron acceptor other than O2 is used in electron transport chain leading to a proton motive force.

In contrast to aerobic respiration where O2 is used as electron acceptor, the electron acceptors used in anaerobic respiration include nitrate (NO–,3)), sulphate (SO2-4), carbonate (CO2), ferric ion (Fe3+), and even certain organic compounds (e.g., fumarate, chlorate, trimethylamine oxide, etc.)

2) The bacteria are fed a sugar and amino acid solution by the squid

3) large intestine has the largest number of bacteria compared to other areas of the gastrointestinal tract

4) answer is. B

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