Any of a diverse group of bacteria that are capable of metabolizing sulfur and its compounds and are important in the sulfur cycle.
Members of the genus Thiobacillus , widespread in marine and terrestrial habitats, react with sulfur to produce sulfates useful to plants; in deep ground deposits they generate sulfuric acid, which dissolves metals in mines and corrodes concrete and steel. Desulfovibrio desulficans reduces sulfates in waterlogged soils and sewage to hydrogen sulfide, a gas with the common rotten-egg odour.