Geobacter luticola sp. nov., an Fe(III)-reducing bacterium isolated from lotus field mud

Abstract

A novel species of Fe(III)-reducing bacterium, designated strain OSK6T, belonging to the genus Geobacter , was isolated from lotus field mud in Japan. Strain OSK6T was isolated using a solid medium containing acetate, Fe(III)-nitrilotriacetate (NTA) and gellan gum. The isolate is a strictly anaerobic, Gram-negative, motile, straight rod-shaped bacterium, 0.6–1.9 µm long and 0.2–0.4 µm wide. The growth of the isolate occurred at 20–40 °C with optima of 30–37 °C and pH 6.5–7.5 in the presence of up to 0.5 g NaCl l−1. The G+C content of the genomic DNA was determined by HPLC to be 59.7 mol%. The major respiratory quinone was MK-8. The major fatty acids were 16 : 1ω7c and 16 : 0. Strain OSK6T was able to grow with Fe(III)-NTA, ferric citrate, amorphous iron (III) hydroxide and nitrate, but not with fumarate, malate or sulfate as electron acceptors. Among examined substrates grown with Fe(III)-NTA, the isolate grew on acetate, lactate, pyruvate and succinate. Analysis of the near full-length 16S rRNA gene sequence revealed that strain OSK6T is closely related to Geobacter daltonii and Geobacter toluenoxydans with 95.6 % similarity to the type strains of these species. On the basis of phylogenetic analysis and physiological tests, strain OSK6T is described as a representative of a novel species, Geobacter luticola sp. nov.; the type strain is OSK6T ( = DSM 24905T = JCM 17780T).