What is the role of autotrophic bacteria in the development of life on earth?

Life on Earth developed gradually. With the appearance of the first heterotrophic protozoa, a problem arose – if these microorganisms continue to eat each other, they will soon die out due to lack of food. As a result of this ecological crisis and evolution, a new type of nutrition emerged – autotrophic. Autotrophic bacteria were able to use sunlight to synthesize essential nutrients for nutrition, and photosynthesis appeared. A side effect of photosynthesis was the release of oxygen, a strong oxidant that was fatal to those creatures, since they were anaerobic (did not use oxygen). Oxygen bubbles rose from the ocean floor and accumulated near the surface of the water. The oxygen concentration in the Earth’s atmosphere began to rise. In fact, autotrophic bacteria have formed a composition of the planet’s atmosphere that is roughly similar to the current one. If not for them, then the air of the Earth would not contain oxygen.