[Anaerobic reduction of ferric iron by hydrogen bacteria]

Ferric iron is a possible electron acceptor for facultative anaerobic processes. A Pseudomonas culture capable of reducing ferric iron with molecular hydrogen has been isolated from marshy soil. The microorganism can grow because of iron reduction. It reduces ferric hydroxide and ferrihydrite, including residues of iron bacteria. The organism reduces also nitrates in nitrites. Reduced iron and nitrite inhibit the growth of the organism, and therefore the concentration of the cells and of reduced iron is not high. The organism can grow with oxygen as an electron acceptor, even at oxygen concentrations below 1%. The organism requires small quantities of yeast extract for growth under both aerobic and anaerobic conditions. The bacterial reduction of iron with hydrogen may be significant for gaining better insight into processes occurring in flooded soils.