Degradation of forchlorfenuron by nitrification and denitrification reactions in the gut and shell biofilm of Limnoperna fortunei
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The capacity and mechanism of Limnoperna fortunei to reduce the concentration of forchlorfenuron [or 1-(2-chloropyridin-4-yl)-3-phenylurea (CPPU)] in water has been studied under laboratory conditions. Firstly, the evasive response of mussels to CPPU (10, 20, 40 and 60 mg L−1) was evaluated, and a toxicity test was carried out at these concentrations. Secondly, the effect of two different sizes of mussels on CPPU concentrations was investigated in a 24-day experiment. Thirdly, the role of intact mussels and valvae only were respectively evaluated in another 24-day experiment. The CPPU concentration decreased by about 40 % in the presence of large mussels and about 20 % in the presence of valvae only. Finally, nucleic acid extracts from the gut and biofilm microbial communities of L. fortunei were analyzed, and the number of copies of the bacterial genes amoA, nirK and nirS were determined. Based on these results, we propose possible mechanisms for CPPU degradation involving bacteria-associated nitrification and denitrification reactions. In summary, we found that the CPPU half-life depended on the presence of mussels, their size and their associated microorganisms.
KeywordsForchlorfenuron Limnoperna fortunei Microorganism Denitrification Nitrification Freshwater
The authors would like to acknowledge the financial support for this work provided by the National Natural Science Foundation of China (Grants No. 51378217 and No. U1360101), Guangdong Provincial Department of Science and Technology Department (No. 2012A010800006) and Guangdong Natural Science and Foundation (No. S2012020010887).
Conflict of Interest
The authors declare that they have no conflict of interest.
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