Bacterial degraders of polycyclic aromatic hydrocarbons isolated from salt-contaminated soils and bottom sediments in salt mining areas

Fifteen bacterial strains capable of utilizing naphthalene, phenanthrene, a nd biphenyl as the sole sources of carbon and energy were isolated from soi ls and bottom sediments contaminated with waste products generated by chemi cal- and salt-producing plants. Based on cultural, morphological, and chemo taxonomic characteristics, ten of these strains were identified as belongin g to the genera Rhodococcus, Arthrobacter; Bacillus, and Pseudomonas. All t en strains were found to be halotolerant bacteria capable of growing in nut rient-rich media at NaCl concentrations of 1-1.5 M. With naphthalene as the sole source of carbon and energy, the strains could grow in a mineral medi um with 1 M NaCl. Apart from being able to grow on naphthalene, six of the ten strains were able to grow on phenanthrene; three strains, on biphenyl; three strains, on octane; and one strain, on phenol. All of the strains wer e plasmid-bearing. The plasmids of the Pseudomonas sp. strains SN11, SN101, and G51 are conjugative, contain genes responsible for the degradation of naphthalene and salicylate, and are characterized by the same restriction f ragment maps. The transconjugants that gained the plasmid from strain SN11 acquired the ability to grow at elevated NaCl concentrations. Microbial ass ociations isolated from the same samples were able to grow at a NaCl concen tration of 2.5 M.