Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Phototrophic bacteria are a group of bacteria that obtain their energy from light through the process of photosynthesis. They can be found in a variety of environments including aquatic and terrestrial ecosystems.
Phototrophic bacteria can be classified into two main groups: oxygenic phototrophs (e.g., cyanobacteria) and anoxygenic phototrophs (e.g., purple sulfur bacteria).
Oxygenic phototrophs produce oxygen as a byproduct of photosynthesis, while anoxygenic phototrophs do not.
These bacteria contain specialized pigments, such as chlorophyll in oxygenic phototrophs and bacteriochlorophyll in anoxygenic phototrophs, to capture light energy.
Phototrophic bacteria play a crucial role in carbon and nitrogen cycles by fixing CO2 and sometimes N2 into organic compounds.
Some phototrophic bacteria can switch between photoautotrophic and chemoheterotrophic modes depending on the availability of light.