【微生物-矿物界面电子转移】David J. Richardson Julea N. Butt and Thomas A. Clarke. Controlling electron transfer at the microbe–mineral interface. PNAS May 7 2013 vol. 110 no. 19 7537-7538
Remarkably many bacteria live and thrive in the earth’s subsurface by respiring extracellular insoluble minerals. Okamato et al. (1) in PNAS report how this process may be accelerated by the presence of flavins that bind as cofactors to electron transport proteins on the cell surface that are key to extracellular mineral respiration.
Humans obtain the energy needed for life by respiring oxygen. This process involves using electrons extracted from food to reduce oxygen into water in our mitochondria. Free energy is released in this process and we use this to make ATP which is the universal energy currency of life. Our dependency on oxygen makes us obligate aerobes—take away the oxygen and we die. Thus humans are confined to living on the surface of planet Earth where oxygen is freely available. However the vast proportion of the earth’s habitable environments is not exploited by humans but by a diversity of microorganisms including bacteria that can live in the absence of oxygen through a process called anaerobic respiration.
Some of the best studied anaerobic respiratory electron acceptors are water soluble such as nitrate or sulfate and these anions can be transported relatively easily into bacterial cells where their respiratory reduction occurs. However insoluble minerals particularly minerals of iron and manganese represent some of the most abundant respiratory substrates in the earth's subsurface environments. In fact “mineral iron respiration” is among the most widespread respiratory processes in anoxic zones and so has wide environmental significance (2⇓–4). For example it directly impacts on the balance of several biogeochemical cycles such as the nitrogen sulfur and carbon cycles and in turn influence the release of potent greenhouse gases such as nitrous oxide.
In some aspects the way bacteria respire mineral iron (or manganese) is similar to the way in which our …
