Desulfotignum toluenicum sp nov., a novel toluene-degrading, sulphate-reducing bacterium isolated from an oil-reservoir model column

A Gram-negative, sulphate-reducing bacterium (strain H3(T)) was isolated from an oil-reservoir model column. The new isolate was able to oxidize toluene coupled to hydrogen sulphide production. For growth, the optimum salt concentration was 1.5% (w/v), the optimum pH was 7.2 and the optimum temperature was 34 degrees C. The cells were straight to slightly curved rods, 0.6-1.0 mu m in diameter and 1.4-2.5 mu m in length. The predominant fatty acids were C-16:0, C-16:1 omega 7c and C-17:0 cyclo, and the cells also contained dimethylacetals. Cloning and sequencing of a 1505 bp long fragment of the 16S rRNA gene showed that strain H3(T) is a member of the Deltaproteobacteria and is related closely to Desulfotignum balticum DSM 7044(T). The G + C content of the DNA was 52.0 mol% and the DNA-DNA similarity to D. balticum DSM 7044(T) was 56.1%. Based on differences in DNA sequence and the unique property of toluene degradation, it is proposed that strain H3(T) should be designated a member of a novel species within the genus Desulfotignum, for which the name Desulfotignum toluenicum sp. nov. is proposed. The type strain is H3(T) (=DSM 18732(T) =ATCC BAA-1460(T)).