2,4-Dichrolophenoxyacetic Acid-degrading Genes from Bacteria Isolated from Soil in Japan: Spread of Burkholderia cepacia RASC-type Degrading Genes Harbored on Large Plasmids

Abstract

Fourteen strains of 2,4-dichrolophenoxyacetic acid (2,4-D)-degrading bacteria were isolated from soil samples from eight different sites in Japan and identified as members of the genera Burkholderia, Cupriavidus, and Sphingobium. To characterize them in view of the 2,4-D-degrading genes that they had, the strains were divided into three groups based on similarities of PCR-amplified partial nucleotide sequences of their 2,4-D-degrading genes to the sequences of well-characterized 2,4-D-degrading genes, tfdA, tfdB, and tfdC in Cupriavidus necator strain JMP134, Achromobacter xylosoxidans strain EST4002, and Sphingomonas sp. strain TFD44. The nucleotide sequences of the tfdA, tfdB, and tfdC gene homologs in eight of the 14 strains were highly similar to those in Burkholderia cepacia strain RASC. The eight strains were classified into the RASC subgroup in the EST4002 group. Southern hybridization indicated that at least one set of the putative tfdA, tfdB, and tfdC genes in each of the 14 strains was located on a replicon (ca. 90-600 kb). In particular, the RASC-type 2,4-D-degrading genes of the eight strains were located on plasmids of similar size (ca. 600 kb), and the hybridization experiments suggested that the 2,4-D-degrading genes of seven strains among the eight were located on restriction fragments of the same length. In view of the fact that the seven strains originated from six distant sites in Japan and had different 16S rRNA gene sequences, our results suggest that the RASC-type 2,4-D-degrading genes on similar plasmids were horizontally transferred among bacteria and were distributed throughout Japan.

A 2,4-dichlorophenoxyacetic acid degradation plasmid pM7012 discloses distribution of an unclassified megaplasmid group across bacterial species

“…2). The organization of the tfd gene cluster in strain RASC, in which the partial nucleotide sequences of tfdA, tfdB and tfdC have ¢98 % similarity to those of pM7012 (Sakai et al, 2007), has not been reported. The second tfd gene cluster, tfdC II E II B II in pM7012, was not a simple duplication of part of the first gene cluster, tfdB I E I C I D I R I .…”

“…strain NK8 (Francisco et al, 2001) and C. necator strain NH9 (Ogawa & Miyashita, 1995) as recipients, and strains M701 and other strains with pM7012-like plasmids obtained in the previous work (Sakai et al, 2007) as donors. However, no transconjugant was detected in this experimental system.…”

Effect of Three Organophosphorous Nematicides on Non-target Nematodes and Soil Microbial Community

“…However, there is growing concern over the increased use of such pesticides 29) , as well as over the microbial community that degrades and thus detoxifies penticides 11,33) . The fumigation of soil suppresses not only target plant-parasitic nematodes but also non-target free-living nematodes and microbes.…”

A Great Leap forward in Microbial Ecology

“…They also characterized a 2,4-D-and 2,4,5-T-degrading enrichment culture by 16S rRNA and benA gene-targeted PCR-DGGE, and suggested the major role of Burkholderia species in degrading these chemicals (51). Sakai et al (138) reported that the Burkholderia cepacia RASC type 2,4-D-degrading genes harbored on large plasmids spread out among 2,4-D-degrading bacteria isolated from soil in Japan. A soil bacterial community capable of degrading 3-chlorobenzoate was characterized by 16S rRNA and benA gene-targeted PCR-DGGE (112,113).…”