Comparative genomics of the genus Desulfitobacterium.

The Desulfitobacterium genus comprises anaerobic Gram-positive bacteria, of which the majority are facultative organohalide respirers. We here present the genomes of eight strains of Desulfitobacterium spp., including five strains of Desulfitobacterium hafniense, one strain each from D. dichloroeliminans and D. metallireducens, and one strain that had not been assigned to any species prior to this study. The newly sequenced genomes were compared with four previously published desulfitobacterial genomes. The average genome sizes are 5.5, 4.3 and 3.4 Mbp for D. hafniense, D. dehalogenans and D. dichloroeliminans/metallireducens, respectively. The genomes encode up to seven reductive dehalogenases, the genomes of both D. hafniense DP7 and D. metallireducens 853-15AT did not encode any reductive dehalogenase. The latter result was a surprise as D. metallireducens 853-15AT has been reported to carry out organohalide respiration. Unlike reported for the pceABCT gene cluster, the other reductive dehalogenase gene clusters do not show any signs of being genetically mobile. All analyzed desulfitobacterial genomes encode a complete cobalamin synthesis pathway. A menaquinone synthesis pathway was found in all strains except D. dichloroeliminans DCA1T. The detailed analysis of the genome sequence of 12 desulfitobacteria from four different species confirmed that this genus has an extremely large metabolic repertoire.