Molecular biological characterization of biphenyl-degrading bacteria and identification of the biphenyl 2,3-Dioxygenase α-subunit genes

Abstract

Bacterial isolates from soils contaminated with (chlorinated) aromatic compounds, which degraded biphenyl/chlorinated biphenyls (CB) and belonged to the genera Rhodococcus and Pseudomonas were studied. Analysis of the 16S rRNA gene sequences was used to determine the phylogenetic position of the isolates. The Rhodococcus cells were found to contain plasmids of high molecular mass (220-680 kbp). PCR screening for the presence of the bphA1 gene, a marker indicating the possibility for induction of 2,3-dioxygenase (biphenyl/toluene dioxygenase subfamily) revealed the presence of the bphAl genes with 99-100% similarity to the homologous genes of bacteria of the relevant species in all pseudomonad and most Rhodococcus isolates. A unique bphA1 gene, which had not been previously reported for the genus, was identified in Rhodococcus sp. G10. The absence of specific amplification of the bphA1 genes in some biphenyl-degrading bacteria (Rhodococcus sp. B7b, B106a, G12a, P2kr, P2(51), and P2m), as well as in an active biphenyl degrader Rhodococcus ruber P25 indicated the absence of the genes encoding the proteins of the biphenyl/toluene dioxygenase subfamily and participation of the enzymes other than this protein family in biphenyl/CB degradation.