Final answer:
Anoxygenic bacteria, such as purple sulfur bacteria, use compounds other than water in anoxygenic photosynthesis and do not release oxygen. They are distinct from oxygenic phototrophs that split water to replenish electrons in photosynthesis, releasing oxygen in the process.
Step-by-step explanation:
Anoxygenic bacteria are not capable of oxidizing water to release oxygen. Instead, they engage in anoxygenic photosynthesis, using different electron donors such as hydrogen sulfide (H2S) for their metabolic processes.Anoxygenic photosynthesis does not produce oxygen as a byproduct, setting it apart from oxygenic photosynthesis performed by plants and cyanobacteria, where water (H2O) is used as the electron donor, releasing oxygen. This process has been pivotal in shaping Earth's atmosphere. Initially, the atmosphere lacked oxygen, and organisms relied on anaerobic processes.
The transition of some bacteria to use water as an electron donor allowed the release of molecular oxygen. However, anoxygenic photosynthetic bacteria, such as purple and green sulfur bacteria, utilize other compounds instead of water and do not contribute to oxygen production.Specific examples of anoxygenic phototrophs include purple sulfur bacteria like Chromatium, which use sulfites as electron donors. These bacteria conduct photosynthesis without generating oxygen, hence the term 'anoxygenic'. An example of an anaerobic process is the function of Nitrosomonas and Nitrobacter, which oxidize ammonia and nitrites respectively, but not by using water as an electron donor.