Photoferrotrophy

Photoferrotrophy is a form of anoxygenic photosynthesis that utilizes ferrous iron (Fe(II)) as an electron donor. This process is carried out by certain bacteria and archaea, collectively known as photoferrotrophic bacteria. Unlike oxygenic photosynthesis which produces oxygen as a byproduct, photoferrotrophy does not release oxygen. Instead, it generates ferric iron (Fe(III)) or other oxidized iron species.

The overall reaction for photoferrotrophy can be simplified as: 4Fe(II) + CO2 + H2O + light -> 4Fe(III) + CH2O + 2H+. In this process, light energy is harnessed by pigments, typically bacteriochlorophylls, to drive the oxidation of Fe(II). The electrons released from Fe(II) are then used to reduce carbon dioxide into organic matter, similar to other photosynthetic organisms.

Photoferrotrophic organisms are found in environments rich in dissolved ferrous iron and light, such as anoxic freshwater lakes, marine sediments, and hydrothermal vents. They play a significant role in the biogeochemical cycling of iron and carbon in these ecosystems. Their metabolic activity can contribute to the formation of iron-rich deposits and influence the geochemistry of aquatic environments. Understanding photoferrotrophy is important for fields like geomicrobiology, astrobiology (as a potential ancient metabolic pathway), and environmental science.

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