Why Sequence Rhodopseudomonas palustris strain DX-1?

To date, six strains of Rhodopseudomonas palustris have been sequenced, all by the JGI, but the strain to be sequenced under this proposal has a most shocking ability: it is exoelectrogenic. In other words, it can directly generate electricity from the biodegradation of organic and inorganic matter. In fact, it produces very high power densities in low-internal-resistance microbial fuel cells (MFCs), a technology that shows great promise as a method of bioelectricity production from waste biomass.

In an MFC, exoelectrogenic bacteria oxidize organic matter and transfer electrons to the anode, where they flow to the counter electrode (cathode) and react with protons and oxygen to form water. Our ability to understand factors that affect electricity generation by exoelectrogenic bacteria has been limited by a lack of high-power-producing strains of microorganisms. While some iron-reducing bacteria are known to be able to generate electricity, few microorganisms have been directly isolated from MFCs. Although not many direct comparisons have been made, all isolates so far examined show power densities equal to or less than those produced by acclimated mixed cultures under otherwise identical conditions. The photosynthetic bacterium Rhodopseudomonas palustris strain DX-1, however, can produce higher power densities than mixed cultures in the same MFC. We anticipate that genome sequence comparisons between DX-1 and the other sequenced strains of R. palustris will reveal key biochemical characteristics of strain DX-1 that are critical for its ability to generate power. The genome sequence will be used to develop and test hypotheses about biological mechanisms that drive electricity generation by strain DX-1 and by bacteria in general. The sequence would also make R. palustris strain DX-1 readily accessible as a model organism (along with Shewanella and Geobacter) for MFC investigations.

Principal Investigator: Caroline S. Harwood (Univ. of Washington) and Bruce E. Logan (Pennsylvania State Univ.).

Program: CSP 2009