Photoautotroph

Synonyms

Photosynthetic organism

Definition

Photoautotrophs are organisms that obtain cellular energy from radiation and assimilate CO₂ as a source of carbon. They differ from photoheterotrophs that produce ATP using solar energy but obtain carbon for biosynthesis from reduced organic compounds. The photosynthesis reaction center of photoautotrophic organisms contains chlorophyll, a pigment responsible for the transduction of radiation into cellular energy. Photoautotrophs can be divided in two groups, anoxygenic and oxygenic, depending on the number of reaction centers in their photosynthetic apparatus and on their ability to use water as a source of reducing power and generating oxygen as a by-product. Anoxygenic photoautotrophs are dependent on environmental reducing power to assimilate CO₂. From an ecological point of view, life on Earth has been considered to be dependent on photoautotrophy; however, the recent discovery of underground strict chemolithoautotrophs is challenging...