Screening and degrading characteristics and community structure of a high molecular weight polycyclic aromatic hydrocarbon-degrading bacterial consortium from contaminated soil

Inoculation with efficient microbes had been proved to be the most important way for the bioremediation of polluted environments. For the treatment of abandoned site of Beijing Coking Chemical Plant contaminated with high level of high-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs), a bacterial consortium capable of degrading HMW-PAHs, designated 1-18-1, was enriched and screened from HMW-PAHs contaminated soil. Its degrading ability was analyzed by high performance liquid chromatography (HPLC), and the community structure was investigated by construction and analyses of the 16S rRNA gene clone libraries (A, B and F) at different transfers. The results indicated that 1-18-1 was able to utilize pyrene, fluoranthene and benzo[a]pyrene as sole carbon and energy source for growth. The degradation rate of pyrene and fluoranthene reached 82.8% and 96.2% after incubation for 8 days at 30°C, respectively; while the degradation rate of benzo[a]pyrene was only 65.1% after incubation for 28 days at 30C. Totally, 108, 100 and 100 valid clones were randomly selected and sequenced from the libraries A, B, and F. Phylogenetic analyses showed that all the clones could be divided into 5 groups, Bacteroidetes, α-Proteobacteria, Actinobacteria, βProteobacteria and γ-Proteobacteria. Sequence similarity analyses showed total 39 operational taxonomic units (OTUs) in the libraries. The predominant bacterial groups were α-Proteobacteria (19 OTUs, 48.7%), γ-Proteobacteria (9 OTUs, 23.1%) and β-Proteobacteria (8 OTUs, 20.5%). During the transfer process, the proportions of α-Proteobacteria and β-Proteobacteria increased greatly (from 47% to 93%), while γ-Proteobacteria decreased from 32% (library A) to 6% (library F); and Bacteroidetes group disappeared in libraries B and F.