The Isolation And Characterization Of Salt-tolerant PAH-degrading Bacteria

Polycyclic aromatic hydrocarbons (PAHs) are a group of ubiquitous and persistent organic pollutants in environment. PAHs, which are of diversity, stability and complicated conformation, high toxicity and bio-refractory, are harmful to human health by biological-chain accumulation. PAHs can hardly be central disposed for their extensive distribution. As one of the PAHs removal methods, biodegradation by the various bacteria widely existing in nature has the superiority to the other methods for its low cost, simple manipulation and no second pollution. Therefore, the study on biodegradation of PAHs is bound to be scientifically useful.The aim was to isolate and characterize the PAH-degrading bacteria,and study the PAH-degrading genes of the bacteria for obtaining some bacteria with high PAH-degrading ability.One kind of PAHs was added into solid medium as the only carbon source to isolate bacterial strains which can degrade PAHs from soil polluted by PAHs. The bacteria strains were identified by physiological and biochemical experiments, and16S rDNA sequence analysis. The phylogenetic trees were formed by MEGA4.0software and analyzed with bootstrapping. As well the hydro xylati on dioxygenase genes of the bacteria were studied.The three bacterial strains were identified, named wjq2, wjq3and wjq7, in which both wjq2and wjq3can degradate naphthalene, wjq7can degradate both naphthalene and phenanthene. Based on the results of16S rRNA anaysis and other tests, those3strains were respectively belonged to Proteobacterium sp., Pseudomonas sp. and Arthrobacter sp. The ranges of salt tolerance concentration of wjq2, wjq3and wjq7were1%-7%,1%-6%and1%-8%respectively. The three strains have a wide range of pH tolerance ranging from4to9.The three bacterial strains are belonged to Proteobacterium sp., Pseudomonas sp. and Arthrobacter sp..They are tolerant with high salt concenntration and a wide range of pH. This is the first report that one bacterial strain of Arthrobacter genus can degrade both naphthalene and phenanthene, which is also tolerant with high-concenntration salt and wide range of pH. These bacterial strains may be helpful for bioremediation of oil-contaminated saline soil.