Desulfitobacterium aromaticivorans sp nov and Geobacter toluenoxydans sp nov., iron-reducing bacteria capable of anaerobic degradation of monoaromatic hydrocarbons

Dissimilatory iron reduction plays a significant role in subsurface environments. Currently, it is assumed that members of the genus Geobacter constitute the majority of the iron-reducing microorganisms that oxidize aromatic compounds in contaminated subsurface environments. Here, we report the isolation of two phylogenetically distinct pure cultures of iron-reducing degraders of monoaromatic hydrocarbons, strain TMJ1(T), which belongs to the genus Geobacter within the Deltaproteobacteria, and strain UKTLT, belonging to the genus Desulfitobacterium within the Clostridia. Both strains utilize a wide range of substrates as carbon and energy sources, including the aromatic compounds toluene, phenol and p-cresol. Additionally, strain UKTLT utilizes o-xylene and TMJ1(T) utilizes m-cresol. Anaerobic degradation of toluene in both strains and o-xylene in strain UKTLT is initiated by activation with fumarate addition to the methyl group. The genomic DNA G+C contents of strains TMJ1(T) and UKTLT are 54.4 and 47.7 mol%, respectively. Based on a detailed physiological characterization and phylogenetic analysis of the 16S rRNA genes of both strains, we propose the names Desulfitobacterium aromaticivorans sp. nov. (type strain UKTLT = DSM 19510(T) = JCM 15765(T)) and Geobacter toluenoxydans sp. nov. (type strain TMJ1(T) = DSM 19350(T) = JCM 15764(T)) to accommodate these strains. To the best of our knowledge, strain UKTLT is the first described spore-forming, iron-reducing bacterium that can degrade aromatic hydrocarbons.