Alkanibacter difficilis gen. nov., sp. nov. and Singularimonas variicoloris gen. nov., sp. nov., hexane-degrading bacteria isolated from a hexane-treated biofilter.

Two Gram-negative, rod-shaped, non-spore-forming bacterial strains were isolated from a hexane-treated, full-scale biofilter from an oil mill. The strains were cultivated with hexane as the sole carbon source. One strain, MN154.3(T), showed a fatty acid profile that contained 16 : 0, 18 : 1cis11 and 19 : 0 cyclo11-12 as major compounds, while the second strain, isolate MN28(T), contained 14 : 0 3-OH, 16 : 0 and 18 : 1cis11 as the predominant fatty acids. On the basis of almost-complete 16S rRNA gene sequences, both strains could be allocated to the Nevskia branch of the class Gammaproteobacteria. The sequence similarities for strains MN154.3(T) and MN28(T) with respect to the most closely related type strains of this branch were 90.5 and 94.1 %, respectively. The sequence similarity between strains MN154.3(T) and MN28(T) was 90.6 %. The DNA G+C content of strain MN154.3(T) was 62.8 mol% and that for strain MN28(T) was 64.9 mol%. Both strains possessed ubiquinone-8 as the major quinone. On the basis of the 16S rRNA gene sequences of these two new isolates and several phenotypic differences exhibited with respect to known species of the Nevskia branch, strains MN154.3(T) and MN28(T) represent two novel genera and species, for which the names Alkanibacter difficilis gen. nov., sp. nov. and Singularimonas variicoloris gen. nov., sp. nov. are proposed. The type strain of Alkanibacter difficilis gen. nov., sp. nov. is MN154.3(T) (=DSM 14804(T)=LMG 22842(T)) and that of Singularimonas variicoloris gen. nov., sp. nov. is MN28(T) (=DSM 15731(T)=LMG 22844(T)).