Thiobacillus is a genus of Gram-negative Betaproteobacteria. Thiobacilus thioparus is the type species of the genus. Whilst over 30 "species" have been named in this genus, most were never validly or effectively published. The remainder were either reclassified into Thiomonas, Paracoccus, Starkeya, Sulfuriferula, Halothiobacillus, Thermithiobacillus or Acidithiobacillus, or were lost from culture.
Most species are obligate autotrophs (using the transaldolase form of the Calvin-Benson-Bassham cycle) using elementary sulfur, thiosulfate or polythionates as energy sources but Thiobacillus aquaesulis can grow weakly on complex media as a heterotroph. Some strains (E6 and Tk-m) of the type species Thiobacillus thioparus can use the sulfur from dimethylsulfide, dimethyldisulfide or carbon disulfide to support autotrophic growth - they oxidise the carbon from these species into carbon dioxide and assimilate it. Sulfur oxidation is achieved via the Kelly-Trudinger pathway.
- Thiobacillus versutus to Paracoccus
- Thiobacillus acidophilus to Acidiphilium
- Thiobacillus intermedius, Thiobacillus perometabolis, Thiobacillus thermosulfatus, and Thiobacilus cuprinus to Thiomonas
- Thiobacillus thiooxidans, Thiobacillus ferrooxidans, Thiobacillus caldus, and Thiobacillus albertensis to Acidithiobacillus
- Thiobacillus neapolitanus, Thiobacillus halophilus, and Thiobacillus hydrothermalis to Halothiobacillus
- Thiobacillus tepidarius to Thermithiobacillus
- Kelly DP; Wood AP (2000). "Reclassification of some species of Thiobacillus to the newly designated genera Acidithiobacillus gen. nov., Halothiobacillus gen. nov. and Thermithiobacillus gen. nov.". International Journal of Systematic and Evolutionary Microbiology. 50: 511–516. doi:10.1099/00207713-50-2-511. PMID 10758854. Retrieved 19 December 2015.