Rhodobacter sphaeroides 2.4.1
Rhodobacter sphaeroides 2.4.1, is a facultative photosynthetic member of the a-3 subgroup of Proteobacteria. In terms of the structural and functional aspects of the light reactions of photosynthesis it is undoubtedly the best studied of all photosynthetic systems. It is also the subject of intensive investigations worldwide on the structure, function and regulation of its photosynthetic membranes, its mechanisms of CO2 fixation, nitrogen fixation, cytochrome diversity and electron transport systems. Crystallization of the photosynthetic reaction center and the application of site-directed mutagenesis is providing fundamental insights into light driven, renewable energy production. Individually and in combination, these areas have been and will continue to be major areas of interest to the DOE.

In addition, R. sphaeroides has been shown to be able to detoxify a number of metal oxides and oxyanions and is the subject of ongoing studies in this area, in keeping with the direct mission of the DOE in bioremediation. Additional investigations over many years have led to increased knowledge of tetrapyrrole and carotenoid biosynthesis, which have broad applicability.

This organism is also the first known free-living bacteriumto be able to utilize the regulatory systems associated with Quorum-Sensing to reversibly initiate the development of a community growth form, perhaps associated with biofilm formation, and a dispersed growth mode, depending upon the quality of the growth medium. These studies are of critical concern to studies of bioremediation and biotechnology. Other very recent studies revealing how an electron transport chain can "communicate" with a variety of genetic elements has led to the development of a new paradigm for gene regulation.