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

A novel species of Fe(III)-reducing bacterium, designated strain OSK6(T), belonging to the genus Geobacter, was isolated from lotus field mud in Japan. Strain OSK6(T) 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 mu m long and 0.2-0.4 mu m wide. The growth of the isolate occurred at 20-40 degrees C with optima of 30-37 degrees C and pH 6.5-7.5 in the presence of up to 0.5 g NaCl I-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 16:1 omega 7c and 16:0. Strain OSK6(T) 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 OSK6(T) 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 OSK6(T) is described as a representative of a novel species, Geobacter Iuticola sp. nov.; the type strain is OSK6(T) (=DSM 24905(T)=JCM 17780(T)).