phototrophic

Phototrophic refers to organisms that harvest light energy to power their cellular processes. In phototrophy, light energy is converted into chemical energy, typically in the form of ATP and reducing equivalents such as NADPH, which may then be used to fix carbon or fuel metabolism.

Photosynthesis is a subset of phototrophy that combines light energy capture with the synthesis of organic matter from carbon dioxide. Organisms that perform photosynthesis may be photoautotrophs, which fix CO2 (e.g., plants, algae, cyanobacteria) or, in some cases, perform oxygenic or anoxygenic photosynthesis. In contrast, photoheterotrophs harvest light for energy but rely on organic carbon sources rather than fixing CO2 (examples include purple non-sulfur bacteria).

Phototrophs occur across all domains of life and in diverse environments. Oxygenic phototrophs, such as land plants, algae, and cyanobacteria, release oxygen to the atmosphere. Anoxygenic phototrophs, including purple and green bacteria, use light energy without producing O2. Some bacteria and archaea employ retinal-based phototrophy (e.g., bacteriorhodopsin) to generate a proton gradient using light, without chlorophyll-based photosynthesis.

Pigments such as chlorophylls, bacteriochlorophylls, and carotenoids enable light capture. Photosynthetic phototrophs possess photosystems and electron transport chains to convert light energy into chemical energy and to fix carbon (in photoautotrophs). The distribution of phototrophy has shaped ecological interactions and biogeochemical cycles throughout Earth's history.