Rhodobacterales

Rhodobacterales is an order of Gram-negative bacteria within the class Alphaproteobacteria, phylum Proteobacteria. The order comprises several families, with Rhodobacteraceae being a prominent example, and includes a variety of genera such as Rhodobacter. Members occur in a wide range of aquatic habitats, including marine and freshwater environments, and some form associations with plants and algae.

Physiology is diverse. A hallmark of many Rhodobacterales is the ability to perform photosynthesis using bacteriochlorophyll under anaerobic conditions, i.e., anoxygenic photosynthesis, often in purple non-sulfur bacteria. They can also be chemoorganotrophs or chemolithotrophs. Metabolic versatility extends to hydrogen production in some species and carbon fixation in others under specific conditions.

Ecology: They are important contributors to carbon and sulfur cycling in aquatic ecosystems. Many members are abundant in coastal and open-ocean microbiomes, and the Roseobacter lineage within the order is a well-known ecologically significant group in marine environments. Some species engage in symbiotic relationships with algae or plants.

Genomics and research: Rhodobacterales species, especially Rhodobacter sphaeroides, are widely used as model organisms to study photosynthesis, respiratory electron transport, and regulatory networks. Their diverse metabolisms and tractability in culture have supported studies in microbial physiology and biotechnological applications.