The Screening, Identification And Degradetion Characteristics Preliminary Study Of The PCBs Degrading Bacteria

At present, environmental issues increasingly become a international problem, and also are being paid more and more attention. The long-term pollution in the environment caused by the aromatic compounds has been the focus of attention in recent years, and is the rapid upward trend, it becomes a serious threat to the production and living of the people. People can use the physical, chemical and integrated approaches to control the pollution of the aromatic compounds, but these methods are generally high cost, incomplete degradation and easily leading to secondary pollution problems. The microbial degradation has the advantages of low cost, good effect and no secondary pollution, so it is the most promising environmental pollution treatment method. We isolate degradation bacteria from the environment, study their biological properties and degradation characteristics, then use them in the environment to achieve a true sense of the cycle degradation processing, and it has important reality sense.In this paper, I isolated relational strains from different soil, after enrichment acclimation culturing them on medium with biphenyl as unique carbon source, and then I screened the strains of the degradation of biphenyl.I compared different strains of degradation efficiency, observed the biological characteristics of the main strain, and used molecular biological methods to identify taxonomic status. Then the main results are as follows:1. PCBs-degrading bacteria screening:I made strains isolated and screened from Zhejiang Taizhou soil as the filter object. By enrichment acclimation culturing on the basic salt medium with biphenyl as sole carbon source,I got the results showing that10strains isolated from Zhejiang Taizhou soil samples could grow with biphenyl as sole carbon source, which showed that the strains tested could degradate PCBs.According to the degradation in the culture medium with biphenyl as sole carbon source and growth curve in the synthesis medium, I got that A1had the best degradation effect.2. The biological characteristics of PCBs-degradating bacteria A1:The bacteria assumed a round or subrounded, white, transparent, smooth-faced, swelling bacterial colony with a neat fringe. Meanwhile it was Gram-negative, nonproductive of hydrogen sulfide, able to decompose starch, unable to break down gelatin, and shows negative in MR、VP experiments, disintegrates citrate. The bacteria could grow in culture medium containing drugs of penicillins, cephalosporins, gentamicins and chloramphenicols, showing strong resistance.The A1strain growed well in LB during0-48h, showing considerable growth rate, while the growth reaches steady stage or decline stage inevitably in48-96h. However, when in synthetic medium it grows with a high speed, even maintain a growth mode in the late period of0-96h.3. Molecular identification of the strain A1:Treating the DNA of strain A1as a template, using the bacterial universal primers(Seq:27f-AGAGTTTGATCCTGGCTCAG1492r-ACGGCTACCTTGTTACGACT) for PCR amplification,getting1450-1500bp segments. Then sequence analysis and phylogenetic tree analysis showed that:the phylogenetic relationship of A1was closest to Pandoraea norimbergensis, sequence homology of100%.So the PCBs degradation bacterium A1was identified as Pandoraea norimbergensis.4. Degradation characteristics of Al:By studying the effectiveness of pH, temperature, substrate concentration, liquid medium volume, and incubation time respectively, we drawed a conclusion that when pH=7, temperaturewas equal to30℃, initial substrate concentration was150mg/L, incubation time wass set to7d and30ml liquid medium was loaded in250ml Petri dish, bacterial strains had a best growth and made a best performance of degradation of PCBs.