Degradation of Mono-Hydroxybiphenyls by Aerobic Strains Isolated from the Bacterial Associations Breaking Down Aromatic Pollutants

Micrococcus sp. PNS1, Ochrobactrum sp. PNS5, Stenotrophomonas sp. PNS6, Pseudomonas sp. PNB3, Brevibacterium sp. PNB5, Achromobacter sp. PNB6, and Bosea sp. PNB7 were isolated from the PN2 and PN2-B associations and screened for their ability to degrade mono-hydroxylated biphenyls with hydroxyl groups at the C 3 or C 4 atoms in the biphenyl molecule. The maximum degradation efficiency was 98 % for 3-hydroxybiphenyl and up to 100 % for 4-hydroxybiphenyl with various strains. All strains showed amplification of a fragment of the bph A gene encoding biphenyl-2,3-dioxygenase biosynthesis. Sequence analysis of the bph A gene revealed a distinct branch on the tree topology, indicating its similarity level with known sequences of this gene. Pseudomonas sp. PNB3 was found to possess the ben A gene encoding benzoate-1,2-dioxygenase biosynthesis and positioned on the same evolutionary branch as the benA gene from the well-known biphenyl degrader Pseudomonas putida KT2440. The results obtained demonstrate that the transformation of 3-hydroxy- and 4-hydroxybiphenyls by the isolated strains occurs through dioxygenation of the unsubstituted ring of the biphenyl molecule, with subsequent cleavage into 3- and 4-hydroxybenzoic acids, respectively. Therefore, the strains that were examined are promising for potential application in technologies aimed at degrading both chlorobiphenyls and hydroxylated biphenyls.