Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism

An isolate, designated GC-29, that could incompletely oxidize glucose to ac etate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This me tabolism yielded energy to support cell growth. Strain GC-29 is a facultati vely anaerobic, Gram-negative motile rod which, in addition to glucose, als o used sucrose, lactate, pyruvate, yeast extract, casamino acids or H-2 as alternative electron donors for Fe(III) reduction. Stain GC-29 could reduce NO3-, Mn(IV), U(VI), fumarate, malate, S2O32-, and colloidal S-0 as well a s the humics analog, 2,6-anthraquinone disulfonate. Analysis of the almost complete 16S rRNA sequence indicated that strain GC-29 belongs in the Shewa nella genus in the epsilon subdivision of the Proteobacteria. The name Shew anella saccharophilia is proposed. Shewanella saccharophilia differs from p reviously described fermentative microorganisms that metabolize glucose wit h the reduction of Fe(III) because it transfers significantly more electron equivalents to Fe(III); acetate and carbon dioxide are the only products o f glucose metabolism; energy is conserved from Fe(LII) reduction; and gluco se is not metabolized in the absence of Fe(III). The metabolism of organism s like S, saccharophilia may account for the fact that glucose is metaboliz ed primarily to acetate and carbon dioxide in a variety of sediments in whi ch Fe(III) reduction is the terminal electron accepting process. (C) 1998 A cademic Press.