title: Comparison of the complete genome sequences of four γ-hexachlorocyclohexane-degrading bacterial strains: insights into the evolution of bacteria able to degrade a recalcitrant man-made pesticide.
abstract: 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.
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Michiro
authors: M
authors: Tabata
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Satoshi
authors: S
authors: Ohhata
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Yuki
authors: Y
authors: Nikawadori
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Kouhei
authors: K
authors: Kishida
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Takuya
authors: T
authors: Sato
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Toru
authors: T
authors: Kawasumi
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Hiromi
authors: H
authors: Kato
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Yoshiyuki
authors: Y
authors: Ohtsubo
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan.
authors: Masataka
authors: M
authors: Tsuda
authors: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Sendai 980-8577, Japan aynaga@ige.tohoku.ac.jp.
authors: Yuji
authors: Y
authors: Nagata
mesh_terms: D001673:Biodegradation, Environmental; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D001556:Hexachlorocyclohexane / Q000378:metabolism*; D010575:Pesticides / Q000378:metabolism*; D016415:Sequence Alignment; D020578:Sphingomonas / Q000235:genetics* / Q000378:metabolism
chemical_list: D010575:Pesticides; D001556:Hexachlorocyclohexane
keywords: evolution; genome; mobile genetic elements; sphingomonads; xenobiotics