Green sulfur bacteria are unique organisms that rely on sunlight for energy and have special structures called chlorosomes to capture light efficiently. They live in dark, sulfide-rich environments where they play a key role in recycling sulfur compounds. These bacteria are sensitive to oxygen and depend on light for survival, making them important in their ecological niche. Green sulfur bacteria are part of the Chlorobi phylum and are known for their obligate phototrophic metabolism. Their ability to thrive in low-light conditions and efficiently harvest light makes them crucial in the oxidation of sulfur compounds in their environment.