Your first assignment is to provide information to the firm BigMoney Inc., a chemical producer in Kansas interested in using microbes to clean toxic spills (bioremediation). BigMoney Inc. has had a major spill of inorganic S that contaminated the soil around their plant. Scientists at BigMoney have developed mechanisms for removing H2S from soil, but have not found one for S. They want to know on a strictly theoretical basis (regardless of whether bacteria exist in nature that actually do these specific reactions) if there are any types of bacteria that could use S to give rise to H2S. (7 points total)
S ? H2S (-0.274)
a) is this an oxidation or reduction?
b) is S serving as an electron acceptor or donor?
c) Which of the following metabolisms (aerobic respiration, anaerobic respiration, aerobic chemolithotrophy and anaerobic chemolithotrophy) could be used to carry out this reaction? You can assume the reaction given above is either the initial oxidation reaction or the final reduction reaction. You must think about whether each of these metabolisms can oxidize or reduce inorganic materials. Remember, think strictly theoretically. Note, you must indicate ALL metabolisms that could be used. (1 point)
d) For each of the metabolisms that could be used, describe exactly how H2S will be formed providing the following information: (5 points)
Is the initial electron donor (from where are the electrons being taken) organic or inorganic?
Which of the pathways discussed in class (glycolysis, TCA, electron transport chain, chemolithotrophy, photosynthesis, and fermentation) will be used to get the electrons?
Is the final electron acceptor oxygen or not oxygen, and is it organic or inorganic?
Please provide a specific example of a half reaction (either initial oxidation or final reduction) that would work with the half reaction provided in this scenario, and briefly describe why it was chosen. Hint: your answer must consider the reduction potential of the electron acceptor compared to that of the electron donor and the half equation given must be either the donating or accepting reaction. Note: you may assume other molecules, both organic and inorganic, are present in the soil.