Impacts of gene bioaugmentation with pJP4-harboring bacteria of 2,4-D-contaminated soil slurry on the indigenous microbial community |
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Authors: | Daisuke Inoue Yuji Yamazaki Hirofumi Tsutsui Kazunari Sei Satoshi Soda Masanori Fujita Michihiko Ike |
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Institution: | (1) Division of Sustainable Energy and Environmental Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan |
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Abstract: | Gene bioaugmentation is a bioremediation strategy that enhances biodegradative potential via dissemination of degradative
genes from introduced microorganisms to indigenous microorganisms. Bioremediation experiments using 2,4-dichlorophenoxyacetic
acid (2,4-D)-contaminated soil slurry and strains of Pseudomonas putida or Escherichia coli harboring a self-transmissible 2,4-D degradative plasmid pJP4 were conducted in microcosms to assess possible effects of
gene bioaugmentation on the overall microbial community structure and ecological functions (carbon source utilization and
nitrogen transformation potentials). Although exogenous bacteria decreased rapidly, 2,4-D degradation was stimulated in bioaugmented
microcosms, possibly because of the occurrence of transconjugants by the transfer of pJP4. Terminal restriction fragment length
polymorphism analysis revealed that, although the bacterial community structure was disturbed immediately after introducing
exogenous bacteria to the inoculated microcosms, it gradually approached that of the uninoculated microcosms. Biolog assay,
nitrate reduction assay, and monitoring of the amoA gene of ammonia-oxidizing bacteria and nirK and nirS genes of denitrifying bacteria showed no irretrievable depressive effects of gene bioaugmentation on the carbon source utilization
and nitrogen transformation potentials. These results may suggest that gene bioaugmentation with P. putida and E. coli strains harboring pJP4 is effective for the degradation of 2,4-D in soil without large impacts on the indigenous microbial
community. |
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