R. palustris has been found to grow in swine waste lagoons, earthworm droppings, marine coastal sediments and pond water. Although purple non-sulfur bacteria are normally photoheterotrophic, R. palustris has the ability to switch between the four different modes of metabolism that support life: photoautotrophic, photoheterotrophic, chemoautotroph and chemoheterotrophic. This means that this bacterium can grow with or without oxygen; it can use light, inorganic compounds, or organic compounds for energy; it can acquire carbon from either carbon dioxide fixation or green plant-derived compounds; and it can also fix nitrogen. This metabolic versatility has raised interest in the research community and makes this bacterium suitable for potential use in biotechnological applications.
Efforts are currently being made to understand how this organism integrates the various metabolic modules in response to environmental changes. The complete genome of the strain Rhodopseudomonas palustris CGA009 was sequenced (List of sequenced bacterial genomes) in the hope of getting more information about how the bacterium senses environmental changes and how it regulates its metabolic pathways accordingly. It was found that R. palustris has genes that encode for proteins that make up light-harvesting complexes and photosynthetic reaction centres. Light-harvesting complexes and photosynthetic reaction centers are typically found in photosynthetic organisms like green plants. Besides being a photosynthetic bacteria R. palustris can modulate photosynthesis according to the amount of light available. For instance, in low-light circumstances it responds by increasing the level of these light-harvesting (LH) complexes that allow light absorption.
R. palustris also has genes that encode for the protein RubisCO, an enzyme that is necessary for carbon dioxide fixation (see Carbon fixation) found in plants and other photosynthetic organisms. The genome reveals also the existence of proteins involved in nitrogen fixation (see Diazotroph).
Purple phototrophic bacteria are of great interest due to their use in biotechnological applications. These bacteria can be used for 'bioplastic' synthesis and hydrogen production. R. palustris differs from other purple bacteria due to is ability to modulate photosynthesis according to the amount of light available and its ability to degrade aromatic compounds found in agricultural and industrial waste. It also has the unique characteristic of encoding for a vanadium-containing nitrogenase, which produces as a byproduct of nitrogen fixation three times more hydrogen than the nitrogenase of other bacteria (molybennum-containing nitrogenase). The potential to manipulate R. palustris to be used as hydrogen production source and biodegradation still requires more detailed knowledge of its metabolic pathways and regulation mechanisms.
- Larimer et al. (2004). "Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris . Nature Biotechnology, 22:55. doi:10.1038/nbt923