During anoxygenic photosynthesis, bacteria primarily produce sulfur compounds as byproducts, not oxygen gas. This can accumulate as granules within the cells or be released into the environment.
Several types of bacteria are capable of performing anoxygenic photosynthesis. These include green sulfur bacteria, Chloroflexia, purple bacteria, acidobacteriota, and heliobacteria. Each of these groups of bacteria has specialized photosynthetic pigments and metabolic processes that allow them to use light energy for carbon fixation in the absence of oxygen.