Analysis of horizontal gene transfer in a mixed bacterial culture for effective biodegradation of xenobiotic chemicals

摘要

Decreasing of bacterial diversity in a biological treatment of xenobiotics by mixed culture is a main reason of causing low degradation rate. In order to enhance the treatment efficiency, application of horizontal transfer of plasmid by conjugation between not only the same species but also different species of bacteria is a promising approach. In the present research, horizontal transfer of a natural TOL plasmid hold in Pesudomonas putida, which encodes enzymes for degradation of toluene and xylene, was examined by culture with Escherichia coli. The plasmid transfer by conjugation was enhanced under static culture, and dependent on the donor cell growth phase. The horizontal transfer process was analyzed successfully by a model consisting of parental bacterial growth and gene transfer kinetics. The Transconjugant was able to maintain the TOL plasmid stably under the presence of selection pressure for a long subculture. From this research, it is suggested that plasmid transfer mediated by conjugation between bacteria of different species is possible for amplifying the biodegradability of a target xenobiotics in a mixed bacterial culture.