Diversity of the bphA1 Genes in a Microbial Community from Anthropogenically Contaminated Soil and Isolation of New Pseudomonads Degrading Biphenyl/Chlorinated Biphenyls

Abstract

Molecular biological and cultivation-based approaches were used to investigate the microbial community of tehnogenic soil contaminated with poorly degradable toxic (chlorinated) aromatic compounds. Diversity of the bphA1 genes, the key genes for the degradation of biphenyl/polychlorinated biphenyls (PCB) was assessed, and new bacterial degraders of biphemyl/PCB were isolated. Cloning of the PCR product obtained using the DNA isolated from soil as a template and the primers to the biphenyl 2,3-dioxygenase α-subunit gene (bphA1) revealed two types of the genes of aromatic dioxygenases (DO) with the highest similarity (97.8‒99.5%) to the genes encoding the Rieske cluster of DO α-subunits (bphA1) from uncultured bacteria. Two biphenyl-degrading isolates obtained from an enrichment culture of a soil sample incubated with biphenyl were identified as Pseudomonas (VRP2-6 and VRP2-2). According to their 16S rRNA gene sequences, they exhibited the highest similarity to the type strain of P. taiwanensis (99%) and P. alcaligenes (100%), respectively. Analysis of the bphA1 sequences of strains VRP2-6 and VRP2-2 revealed the similarity to those of the known biphenyl-degrading pseudomonads not exceeding 97.3%. The isolate VRP2-6 efficiently utilized ortho- and para-monochlorinated biphenyls and degraded dichlorinated biphenyl oxidizing both the ortho- and para-chlorinated rings of the biphenyl molecule. New pseudomonad strains may be of interest for development of biotechnologies aimed at monitoring and remediation of biphenyl/PCB-contaminated soils.