Abstract

Much effort has been focused on microbes that inhabit soil and water and their degradation abilities to chemical pollutants. Few studies were performed on interactions between pollutants and phyllosphere microbes (phyllomicrobes) in plant leaves, although, plant leaves exert critical effects on the quality of agricultural product. In this study, acetamiprid degradation by phyllomicrobes and its ecological effects on phyllobacteria were investigated by in situ and ex situ methods. In situdegradation results showed that the half-lives of 10 µg·ml^-1 acetamiprid on disinfected and natural leafage were 4.99 and 3.24 d, respectively, but the half-lives of 30 and 50 µg·ml^-1 acetamiprid displayed no significant difference on the two kinds of leafage. Ex situ cultivable microbes from phyllosphere of Phaseolus vulgaris completely degraded 11 µg·ml^-1 acetamiprid within 42 days in plant leaves medium (PLM), but not in chemical medium. However, only 30% acetamiprid was decreased within 56 days when acetamiprid concentration increased up to 30 µg·ml^-1 in PLM. Bacterial population investigation and 16S rRNA gene PCR-DGGE (denaturing gradient gel electrophoresis) fingerprints analysis indicated that, low concentration of acetamiprid showed minor effects on phyllobacterial community or population, but phyllobacterial community structure was significantly changed by acetamiprid at the concentration higher than 30 µg·ml^-1. In conclusion, phyllomicrobes of P. vulgaris were able to degrade acetamiprid at the proper concentration, however, phyllomicobes biodegradation capability was inhibited by high concentration of the pesticide and phyllomicrobes’ community was also destroyed at the same conditions.

Key words: Microbial community structure, phyllosphere, acetamiprid degradation, 16S rDNA, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE).