Diversity of tfdC genes: distribution and polymorphism among 2,4-dichlorophenoxyacetic acid degrading soil bacteria

The aim of the present work was to study the occurrence, distribution and d iversity of 1,2-dichlorocatechol dioxygenase genes among 2,4-dichlorophenox yacetic acid degrading bacteria. Phylogenetic relationships between the 31 strains or isolates were evaluated by amplified ribosomal DNA restriction a nalysis of the 16S rDNA gene. All the strains could be assigned to the beta or gamma subdivisions of the Proteobacteria. tfdC genes were detected by P CR amplification using degenerated primers. Two specific probes were produc ed from Ralstonia eutropha strain JMP134 and from a soil isolate strain PLA E6 which was grouped with Variovorax paradoxus. Sequence analysis of the pr obes revealed that they were homologous to the tfdC genes of JMP134 located on plasmid pJP4 and to the tfdC gene of Pseudomonas putida strain PaW85 lo cated on plasmid pEST4011, The localization and the copy number of tfdC gen es were determined by hybridization of plasmid profiles and genomic DNA res triction fragment length polymorphism profiles with the two probes. Most of the strains were found to bear tfdC genes on plasmids ranging from 78 to 5 32 kb; two strains without any plasmids were also found to hybridize with t he probes, revealing a chromosomal localization of catabolic genes. Sequenc e analysis of the PCR products from different strains confirmed that four d ifferent classes of chlorocatechol 1,2-dioxygenase genes were present in th e strains and isolates studied. (C) 1999 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V. All rights reserved.