Plasmid-encoded γ-hexachlorocyclohexane degradation genes and insertion sequences in Sphingobium francense (ex-Sphingomonas paucimobilis Sp+)

Abstract

The lin genes encode the γ-hexachlorocyclohexane (γ-HCH or lindane) catabolic pathway in lindane-degrading strains. The location and stability of these genes have been explored in the lindane-degrading Sphingobium francense strain Sp+, and in two nonlindane-degrading mutants (Sp1- and Sp2-). The lin genes, linA, linB, linE and linX were localized by hybridization on three of the six plasmids of the S. francense strain Sp+ showing dispersal within the genome. The linC gene was detected by PCR, but was not detected by hybridization on any of the plasmids. The hybridization of the linA and linX genes was negative with the two nonlindane-degrading mutants S. francense strains, Sp1- and Sp2-. The dynamic of this genome associated with gene loss and acquisition, and plasmid rearrangement was explored by a search for associated insertion sequences. A new insertion sequence, ISSppa4, belonging to the IS21 family was detected and compared with IS6100 and ISsp1. Insertion sequence localization was explored on different hybridization patterns (plasmid, total genome) with the lindane-degrading Sp+ strain and the two nondegrading derivatives (Sp1-, Sp2-). Insertion sequence movement and plasmid rearrangement could explain the emergence of the nonlindane-degrading mutants. © 2006 Federation of European Microbiological Societies Published by Blackwell Publishing Ltd. All rights reserved.