γ-Hexachlorocyclohexane (γ-HCH) is a recalcitrant man-made chlorinated pesticide. Here, the complete genome sequences of four γ-HCH-degrading sphingomonad strains, which are most unlikely to have been derived from one ancestral γ-HCH degrader, were compared. Together with several experimental data, we showed that (i) all the four strains carry almost identical linA to linE genes for the conversion of γ-HCH to maleylacetate (designated “specific” lin genes), (ii) considerably different genes are used for the metabolism of maleylacetate in one of the four strains, and (iii) the linKLMN genes for the putative ABC transporter necessary for γ-HCH utilization exhibit structural divergence, which reflects the phylogenetic relationship of their hosts. Replicon organization and location of the lin genes in the four genomes are significantly different with one another, and that most of the specific lin genes are located on multiple sphingomonad-unique plasmids. Copies of IS6100, the most abundant insertion sequence in the four strains, are often located in close proximity to the specific lin genes. Analysis of the footprints of target duplication upon IS6100 transposition and the experimental detection of IS6100 transposition strongly suggested that the IS6100 transposition has caused dynamic genome rearrangements and the diversification of lin-flanking regions in the four strains.

γ-Hexachlorocyclohexane (γ-HCH) is a man-made chlorinated insecticide that has caused serious environmental problems. Here, we report the complete genome sequence of the γ-HCH-degrading bacterium Sphingomonas sp. strain MM-1, which consists of one chromosome and five plasmids. All the specific lin genes that are almost identical to those of Sphingobium japonicum UT26 for the conversion of γ-HCH to β-ketoadipate are dispersed on four out of the five plasmids.

Here, we report the complete genome sequence of a γ-hexachlorocyclohexane (γ-HCH) degrader, Sphingobium sp. strain TKS, which was isolated from a γ-HCH-degrading microbial community. The genome of TKS consists of two chromosomes and nine plasmids. The lin genes for conversion of γ-HCH to β-ketoadipate are dispersed on chromosome 1 and three out of the nine plasmids.

Here, we report the complete genome sequence of a γ-hexachlorocyclohexane (γ-HCH)-degrading bacterium, Sphingobium sp. strain MI1205. The genome of MI1205 consists of two chromosomes and four plasmids with sizes of 33 to 292 kb. All the lin genes for γ-HCH metabolism are dispersed on the four plasmids.

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