Context: These processes are also important in biological responses to pollution; for example, sulfate-reducing bacteria are largely responsible for the production of the highly toxic forms of mercury (methyl- and dimethylmercury) in the environment. Non-respiratory anaerobes use fermentation to generate energy and reducing power, secreting metabolic by-products (such as ethanol in brewing) as waste. Facultative anaerobes can switch between fermentation and different terminal electron acceptors depending on the environmental conditions in which they find themselves.

Question: What is sulfate-reducing bacteria accountable for?
Answer: the production of the highly toxic forms of mercury

Question: What is the by-product of non-repiratory anaerobes?
Answer: ethanol

Question: How can anaerobes adjust to the surrounding environment?
Answer: can switch between fermentation and different terminal electron acceptors