7. Your friend Jeffery claims to have isolated a novel bacterial species from de

Question

7. Your friend Jeffery claims to have isolated a novel bacterial species from deep soil but is only able to culture (i.e., grow) this bacterium in the laboratory if he removes molecular oxygen (O2) and includes nitrate (NOs) in the media. Jeffery's confused. What would you tell him? (See the accompanying electron tower ifneeded.) A) This bacterium is using nitrate as a source of nitrogen (N) for DNA and proteins. B) This bacterium is using nitrate as an electron donor. CO) This bacterium is using nitrate as a terminal electron acceptor. D) This bacterium is using nitrate as a source of oxygen (O) for DNA and proteins.

Explanation / Answer

Option C is the correct answer.

This bacterium is using Nitrate as a terminal electron acceptor. The bacteria isolated is most likely to be a anerobic bacteria that performs denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors that is most favourable electrochemically is Nitrate in this this case. Denitrifying microbes require a very low oxygen concentration of less than 10% which explains why the bacterium is able to grow only when molecular oxygen is removed.

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