Deltaproteobacteria is a class of bacteria within the phylum Proteobacteria. They are primarily known for their role in the sulfur and carbon cycles, often found in anaerobic environments such as sediments and the guts of animals. Many species are sulfate-reducing bacteria, which means they can use sulfate as an electron acceptor during respiration, producing hydrogen sulfide as a byproduct. These bacteria are diverse in form and function, including both free-living and symbiotic species. Some members of Deltaproteobacteria are important in bioremediation, helping to break down pollutants in the environment. Their unique metabolic capabilities make them essential for nutrient cycling in ecosystems.