Thiobacillus

Thiobacillus is a genus of Gram-negative, rod-shaped bacteria that oxidize reduced sulfur compounds to derive energy and use carbon dioxide as a carbon source. Members are chemolithoautotrophs, though some species can grow mixotrophically or facultatively heterotrophically under certain conditions. They commonly obtain energy by oxidizing substrates such as sulfide, elemental sulfur, thiosulfate, or sulfite, with oxygen as the typical electron acceptor; some species can alternatively use nitrate in anaerobic or microaerophilic conditions.

Taxonomy and classification: The circumscription of Thiobacillus has changed over time. Many sulfur-oxidizing species previously assigned to Thiobacillus have been reclassified into other genera, notably Acidithiobacillus and Halothiobacillus, in light of phylogenetic analyses. Example: Thiobacillus ferrooxidans is now Acidithiobacillus ferrooxidans. The genus remains a reference for a group of diverse sulfur-oxidizing bacteria, albeit narrower in modern taxonomy.

Habitat and ecological role: Thiobacilli are found in environments that contain reduced sulfur compounds, including soil, freshwater and marine systems, hot springs, and industrial settings such as acid mine drainage. Through oxidation of sulfur compounds, they contribute to sulfur cycling and, in some systems, to the acidification of their surroundings.

Biotechnological relevance: They are exploited in bioleaching and biomining to extract metals from sulfide ores and are studied as model chemolithoautotrophs for energy metabolism. Some species are of interest in environmental biotechnology for sulfur cycling and remediation.