Anoxygenic refers to a type of photosynthesis that does not produce oxygen as a byproduct. This process is primarily carried out by certain bacteria, such as purple sulfur bacteria and green sulfur bacteria. Instead of using water as an electron donor, these organisms typically utilize compounds like hydrogen sulfide or organic molecules, allowing them to thrive in environments where oxygen is scarce. Anoxygenic photosynthesis is significant in various ecosystems, particularly in anoxic environments like deep-sea vents and stagnant water bodies. By converting light energy into chemical energy without releasing oxygen, these bacteria play a crucial role in the global carbon cycle and contribute to the diversity of life in extreme habitats.