Electrolytic respiration supports aerobic and anaerobic bacterial growth

摘要

Bacteria use cellular respiration to convert energy of substrates to a form usable by the cells, a process which entails the electrons transfer from donors to acceptors along a respiratory chain. We therefore hypothesized that if an electrode could be employed as the electron donor or acceptor, it might be possible to artificially control the respiratory electron flow supporting the energy for bacterial growth. Here we describe electrolytic respiration for both aerobic and anaerobic growth of the chemolithoautotrophic bacterium Thiobacillus ferrooxidans. The cathode served as the electron donor for aerobic respiration. The bacterium respired aerobically on the oxidation of Fe~(2+). Fe~(3+) produced by the respiration was regenerated to Fe~(2+) by the electrochemical reduction on the cathode. Therefore, the cathode supplied the electron to the bacterium by the electrolysis through iron as the mediator. The final cell density with the electrolysis reached 10~(10) cells/ml after 6days incubation, which was a 50-fold increase over cultivation without the electrolysis. In the same manner, the cathode served as the terminal electron acceptor for anaerobic respiration of the bacterium, while H_2 served as the electron donor. The bacterium could grow on anaerobic oxidation of H_2 by Fe~(3+). The electron from H_2 was passed to Fe~(3+) through the cells, and the passed electron in Fe~(2+) was finally accepted by the cathode. The electron flow from H_2 to the cathode was mediated by iron, which shuttled electrons between the cells and the cathode, enabling bacterial cultures to reach a density of 10~(10) cells/ ml. The eletrolytic cultivation would be a potentially productive strategy for bacterial cultivation as a result of the conversion of electricity into life energy.