The bacterium Syntrophus aciditrophicus, one of the most extreme-survival organisms ever discovered, has had its genome sequenced.
Syntrophus lives on a diet so austere that it exists on the brink of energetic death. The genes now discovered making up its genome are providing clues as to how it survives, and might even improve the efficiency by which we can make hydrogen from waste materials, the researchers say.
Robert Gunsalus at the University of California, Los Angeles, US, and colleagues, identified 3169 genes in Syntrophus. The bacterium performs a key part of the global carbon cycle by breaking down fatty acids in organic matter – a very limited diet consumed by almost no other organisms. To do this it needs genes that can participate in thermodynamically unfavourable reactions known as reverse electron transport.
Most organisms use oxygen to help breakdown organic compounds for energy use. In this process, organic compounds are chemically oxidised, and the electrons produced in the reaction are used to drive the production of the energy-storage compound ATP.
Syntrophus lives in an anaerobic (non-oxygen) environment, where such a key reaction is impossible. Instead, the flow of electrons occurs in the opposite direction – reverse electron transport – through a reaction that produces hydrogen and formate, which actually requires energy. Without the “help” of other types of bacteria, which consume the hydrogen and formate and provide energy in return, Syntrophus could not survive.
Gunsalus’s team found several genes that appear to participate in this process, and they hope to gain a better understanding of the mechanism. “If we can understand such ‘syntrophic metabolism’, we may be able to increase the amount of hydrogen that can be made from waste materials, and hopefully make biohydrogen production a reality,” says Gunsalus.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0610456104)