Halothiobacillus

Halothiobacillus is a genus of Gram-negative, aerobic, sulfur-oxidizing bacteria. Members are chemolithoautotrophs that obtain energy by oxidizing reduced sulfur compounds such as hydrogen sulfide, thiosulfate, and elemental sulfur, and they fix carbon dioxide via the Calvin-Benson-Bassham cycle. Cells are typically rod-shaped and occur singly or in small aggregates; some species are motile with flagella.

Habitat and ecology: Halothiobacillus species are halophilic or halotolerant and are commonly recovered from saline environments, including seawater, salt flats, hypersaline lakes, brine pools, and industrial brines; some isolates have been found in hydrothermal vent settings.

Physiology: They are generally aerobic chemolithoautotrophs adapted to elevated salinity, with oxygen serving as the terminal electron acceptor during sulfur oxidation.

Genomics and metabolism: Genomes of several species encode sulfur oxidation pathways, notably the Sox multienzyme system, and the Calvin cycle, enabling coupling of sulfur oxidation to carbon fixation. These bacteria contribute to sulfur cycling and primary production in saline habitats.

Taxonomy: Halothiobacillus is placed in the family Halothiobacillaceae within the Gammaproteobacteria.

Notable species: Halothiobacillus neapolitanus and Halothiobacillus halophilus.

Significance: In saline ecosystems, Halothiobacillus species play a role in sulfur cycling and carbon fixation, and they are of interest for understanding adaptation to high-salt conditions as well as potential biotechnological applications in bioremediation of sulfur compounds.