Geobacter hydrogenophilus, Geobacter chapellei and Geobacter grbiciae, three new, strictly anaerobic, dissimilatory Fe(III)-reducers

Recent studies on the diversity and ubiquity of Fe(III)-reducing organisms in different environments led to the isolation and identification of four n ew dissimilatory Fe(III)-reducers (strains H-2(T), 172(T), TACP-2(T) and TA CP-5). All four isolates are non-motile, Gram-negative, freshwater, mesophi lic, strict anaerobes with morphology identical to that of Geobacter metall ireducens strain GS-15(T), Analysis of the 16S rRNA sequences indicated tha t the new isolates belong to the genus Ceobacter, in the delta -Proteobacte ria. Significant differences in phenotypic characteristics, DNA-DNA homolog y and G+C content indicated that the four isolates represent three new spec ies of the genus. The names Geobacter hydrogenophilus sp. nov. (strain H-2( T)), Geobacter chapellei sp. nov. (strain 172(T)) and Geobacter grbiciae sp , nov. (strains TACP-2(T) and TACP-5) are proposed. Geobacter hydrogenophil us and Geobacter chapellei were isolated from a petroleum-contaminated aqui fer and a pristine, deep, subsurface aquifer, respectively. Geobacter grbic iae was isolated from aquatic sediments. All of the isolates can obtain ene rgy for growth by coupling the oxidation of acetate to the reduction of Fe( III). The four isolates also coupled Fe(III) reduction to the oxidation of other simple, volatile fatty acids. In addition, Geobacter hydrogenophilus and Geobacter grbiciae were able to oxidize aromatic compounds such as benz oate, whilst Ceobacter grbiciae was also able to use the monoaromatic hydro carbon toluene.