Sulfur bacteria, also known as sulfide-oxidizing bacteria, are a type of microorganism that are found in various aquatic environments and soil. These bacteria play an important role in the ecosystem as they break down sulfur compounds such as hydrogen sulfide and elemental sulfur, releasing sulfur dioxide and water. Other synonyms for sulfur bacteria include sulfophilic bacteria, sulfuroxidizing bacteria, and sulfur-reducing bacteria. These names reflect the ability of these microorganisms to oxidize or reduce sulfur compounds depending on their energy source. Some well-known sulfur bacteria include Thiobacillus, Beggiatoa, and Desulfobacter, which are commonly used as bioindicators to monitor the health of aquatic ecosystems.