Anoxygenic photosynthesis is a process used by certain bacteria to convert light energy into chemical energy without producing oxygen. This type of photosynthesis occurs in environments where oxygen is scarce, such as deep water or mud. Organisms like purple sulfur bacteria and green sulfur bacteria utilize light to drive the conversion of carbon compounds into energy-rich molecules. In anoxygenic photosynthesis, bacteria use pigments like bacteriochlorophyll to capture light. Instead of water, these bacteria often use substances like hydrogen sulfide or organic compounds as electron donors. This process is essential for the survival of these bacteria and plays a role in the global carbon cycle.