| 研究概要 |
In the first year tenure, two main aspects have been focused, including (1) investigation on rhizoremediation of aromatic compounds in the rhizosphere and (2) investigation on chemical characteristics of root exudates of Spirodela polyrhiza, and activated genes and enzyme of aromatic compounds-degrading bacteria. The important findings from this first year study are summarized as the following :
Objective 1 : In order to obtain useful information of the potential of Spirodela to remove nonylphenol ([NP] ; as model of aromatic compound) from surface water, two cycles batch of NP biodegradation experiment were performed using environmental water (e.g., secondary effluent of wastewater treatment plant [WWTP]) in the present or absence of Spirodela. The results show that in WWTP, removal of NP was accelerated in the presence of Spirodela and we successfully isolated 2 strains from both roots of Spirodela and bulk water. These strains utilized exudates released by plant as their carbon sourc
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e and energy, and efficiently degraded NP. The characterization of degraders and identification of metabolite are still in progress.
Objective 2 : To understand the chemical characteristics of root exudates and its role in the degradation, present study was correlates colonization with chemotaxis and bacterial growth that are connected by Spirodela, induced chemotaxis response in 4- tert-butylphenol-degrading bacterium, Sphingobium fulginis strain OMI (as model of rhizobacteria). The results show that a positive taxis response has been demonstrated by strain OMI along with the higher released of root exudates that has achieved during the first two weeks incubation. During this period, strain OMI was attracted and colonized into the roots. Under exudates deficiency, lower taxis response and growth simulation were observed. However, the population size was still 100 times greater than the intial inoculum size. Indeed, evaluation on single exudate effect has shown that taxis response of strain OMI was mediated by serine and its alteration could induce exclusion of other compounds. Hence, the results suggest that S. polyrhiza colonization is influenced by chemotaxis and bacteria growth and this may be caused by qualitative changes of the composition of root exudates. 隠す
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| 今後の研究の推進方策 |
In the remaining year of tenure, investigation on metabolomics study during alkylphenols (nonylphenol or tert-butylphenol) degradation will be continued, and the applicability of rhizoremediation system in ASIAN region including the screening of several aquatic plants inhabiting in ASIA countries will be accomplished. If in the future, the technical problems will be occurred, samples will be send to the commercial company for further analyses.
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