title: 16S rDNA phylogeny and distribution of lin genes in novel hexachlorocyclohexane-degrading Sphingomonas strains.
abstract: Hexachlorocyclohexane (HCH) is a highly recalcitrant pesticide that persists in soils. Three novel HCH-degrading strains (DS2, DS2-2 and DS3-1) were isolated after enrichment from HCH-contaminated soil from Germany. These strains efficiently degraded the alpha-, gamma- and delta-isomers of HCH, while strain DS3-1 also degraded beta-HCH. Based on 16S rDNA analysis, strain DS3-1 was closely related to Sphingomonas taejonensis, while strains DS2 and DS2-2 were closely related to Sphingomonas flava and seven HCH-degrading strains recently isolated from HCH-contaminated Spanish soil. Hence, geographic origin of the strains was not reflected in their phylogenetic affiliation. Subsequently, lin genes involved in HCH degradation, virtually identical to those from Sphingomonas paucimobilis strains UT26 from Japan and B90A from India, were identified in strains DS3-1, DS2, DS2-2 and five of the strains from Spain. The conserved lin gene sequences and structural organization, as well as the close association with IS6100, suggest a shared lin gene origin and recent horizontal gene transfer among phylogenetically diverged Sphingomonas strains in remote geographic locations. The loss of the ability to degrade gamma-HCH was associated with the deletion of the linA gene, probably due to recombination involving IS6100 elements, of which several copies are located in the lin cluster region.
authors.affiliation: Department of Plant Biochemistry and Molecular and Cellular Biology, Estación Experimental del Zaidín, CSIC, Calle Profesor Albareda 1, Granada 18008, Spain. dietmar.boeltner@eez.csic.es
authors.forename: Dietmar
authors.initials: D
authors.lastname: Böltner
authors.forename: Silvia
authors.initials: S
authors.lastname: Moreno-Morillas
authors.forename: Juan-Luis
authors.initials: JL
authors.lastname: Ramos
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D004275:DNA, Ribosomal / Q000235:genetics*; D005798:Genes, Bacterial; D001556:Hexachlorocyclohexane / Q000737:chemistry*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D016415:Sequence Alignment; D012988:Soil Microbiology; D020578:Sphingomonas / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D001556:Hexachlorocyclohexane