photoorganotrophic

Photoorganotrophic describes organisms that obtain energy from light (phototrophy) and acquire electrons from organic compounds (organotrophy). In these organisms, light drives their metabolic reactions, while organic molecules serve as electron donors rather than inorganic substances such as hydrogen sulfide or ferrous iron. The carbon source for photoorganotrophs can vary: many are photoorganoheterotrophs that use organic carbon, though some may fix CO2 and function as photoorganotrophs with autotrophic carbon fixation depending on the species.

In practice, photoorganotrophy is a subset of phototrophy combined with organotrophy. Most commonly, these organisms perform anoxygenic photosynthesis and rely on organic substrates for both electron donation and, frequently, carbon intake. The terminology emphasizes the source of electrons (organic) rather than the carbon-nutrient strategy alone, which can range from organic carbon uptake to CO2 fixation.

Representative groups include certain purple non-sulfur bacteria and related phototrophic bacteria that can thrive under light in anaerobic or microaerophilic conditions. These organisms are often found in illuminated environments such as freshwater or marine sediments, wetlands, microbial mats, and some soils where light penetrates but oxygen may be limited. Their pigments typically include bacteriochlorophylls and carotenoids, supporting photosynthetic electron transport configured for organic electron donors.

Overall, photoorganotrophy highlights the combination of light-driven energy capture with organic electron donation, distinguishing these organisms from photoautotrophs that rely on inorganic electron donors and from chemoorganotrophs that obtain energy without light. See also phototrophy, organotrophy, heterotrophy.