Abstract:Ferredoxins (Fds) are small proteins containing iron-sulfur clusters. They widely exist in nature and participate in biological physiological processes such as respiration, fermentation, nitrogen fixation, carbon dioxide fixation and hydrogen production, etc. Fd is particularly important for strictly anaerobic bacteria, because the energy metabolism of these organisms is highly dependent on biological components with low redox potential. Fd can flexibly adjust the redox potential by using their iron-sulfur centers to cater to the requirements of different redox potentials. Here, we take the Fd of anaerobic bacteria as examples and summarize related literatures about their structural types and physiological functions. Combined with the relevant work of our group, we dissect the possibility that Fd could produce reactive oxygen species (ROS). It may help to understand the importance of low-potential components such as Fd for anaerobes and could give clues and shed light on the question of intracellular ROS sources.