toxic effects of acetochlor methamidopos and their combinationon nifh gene in soil.pdf

Journal of Environmental Sciences 19(2007) 864–873 Toxic eects of acetochlor, methamidophos and their combination on nifH gene in soil 1 1, 1 SU Zhen-cheng , ZHANG Hui-wen , LI Xin-yu , ZHANG Qin12 , ZHANG Cheng-gang1 1. Key Laboratory of Terrestrial Ecological Process, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. E-mail: zhehchengsu@ 2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China Received 11 September 2006; revised 3 November 2006; accepted 7 February 2007 Abstract Toxic eects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis (DGGE) and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity (both in gene richness and diversity index values) and caused changes in the nifH gene composition. The eects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been aected by low concentration of acetochlor (50 mgkg) recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos (150 mgkg) caused the most apparent changes in nifH gene diversity at the first week while th