Sulfate-reducing bacteria (SRB) are a group of microorganisms that thrive in environments lacking oxygen. They play a crucial role in the sulfur cycle by reducing sulfate ions (SO4^2-) to sulfide (H2S), a process that occurs in various habitats, including marine sediments and anaerobic environments. These bacteria are important for nutrient cycling and can influence the availability of sulfur in ecosystems. They are also studied for their potential in bioremediation, as they can help detoxify environments contaminated with heavy metals and other pollutants by transforming them into less harmful forms.