Study On Distribution Of The Polychlorinated Biphenyls(PCBs)-biodegrading Bacterial Strains And Microarray Analysis Of Plant Phytoremediation

Polychlorinated biphenyls (PCBs), are a large group of chlorinated biphenyls with209possible congeners, are manufactured by the direct chlorination of biphenyl to produce complex mixtures containing up to10chlorines. For a long time, PCBs were used for various industrial and commercial purposes and it is estimated that more than1.5million tons of PCBs have been manufactured worldwide. Unfortunately, due to their hydrophobic properties, PCBs are easily adsorbed by natural organic matter in soil, sludge and aquatic sediments and they have entered the food chain. It was first recorded in the1930s that PCBs are harmful to human health. Since then, PCBs had been proved to cause cancer and to have a number of serious effects on immune, reproductive, nervous and endocrine systems. These health concerns prioritize PCBs as major targets for environmental clean-up.How to degrade PCBs in environment is becoming a research focus in recent years. It can be divided into biodegradation and non-biodegradation.Non-biodegradation includes physical and chemical methods. As the high cost and complex process, people turn to the biodegradation. Biodegradation is the most potential way to remove PCBs. Biodegradation can mainly be divided into microbial degradation, phytoremediation, plant and microbial combined remediation. To constract to the traditional methods, the biodegradation methoed reduce the number of charges. Moreover, biodegradation is a permanent degradation of pollutants, rather than non-biodegration.Sometimes, non-biodegradation may keep the pollutants into another form, that is, secondary pollution. Therefore, the biodegradation of PCBs methods is economical and effective to solve the pollution problems.In this study, soil samples from Shanghai and and other countries were screened for the presence of PCB-degrading bacteria.The16S rDNAs were amplified from those genomes with a bacterial16S rDNA primer and the products were purified and sequenced for the isolation and identification of bacterial species. Some strains from each sample were randomly selected for analysis by HPLC. We used MEGA4software to construct a phylogenetic tree for analysis of the selected strains.In order to understand the informationthe of genes of PCBs-degrading strains, we synthesized dihydroxybiphenyl dioxygenase gene through two-step PCR method (PTDS), whose open reading frame is888bp, obtained295amino acids. A comprehensive survey of global gene expression response to this PCB was done by using Arabidopsis (V4) gene expression microarray (4X44K) to quantify the spatio-temporal variations in transcript abundance of42,000genes. The results revealed a coordinated induction or suppression of146or148genes, respectively. Of these, expression of40genes was validated by RT-PCR analysis. The functional classification of these PCB-responsive genes indicated their involvement in various metabolic pathways, such as ion transport, signal transduction, transcriptional regulation, and other processes related to growth and development.