Chloropyridinyl neonicotinoid insecticides play a major role in crop protection and flea control on cats and dogs. Imidacloprid, thiacloprid and acetamiprid have in common the 6-chloro-3-pyridinylmethyl group but differ in the nitroguanidine or cyanoamidine substituent on an acyclic or cyclic moiety. Our previous study found that Stenotrophomonas maltophilia CGMCC 1.1788 could hydroxylate imidacloprid to 5-hydroxy imidacloprid, and 5-hydroxy imidacloprid was easily converted to 10-19 times higher insecticidal olefin imidacloprid against aphid or whitefly. Acetamiprid could be transformed by S. maltophilia to form N-demethylation product(IM 2-1). In this paper, we examined S. maltophilia CGMCC 1.1788's ability of transformation of thiacloprid. S. maltophilia CGMCC 1.1788 can hydroxylate thiacloprid to 4-hydroxy thiacloprid characterized by HPLC-MS/MS and NMR analysis, however 4-hydroxy thiacloprid could not be converted to olefin thiacloprid under acid conditions like imidacloprid, whereas oxidized and decyonated simultaneously to form 4-ketone thiacloprid imine in alkaline solution. Bioassays indicated that 4-hydroxy thiacloprid had 156 times lower insecticidal activity than thiacloprid, and the ketone-imine derivative almost had no toxicity towards aphid. Though both imidacloprid and thiacloprid are hydroxylated by S. maltophilia CGMCC 1.1788 at the same carbon atom position, however the structural difference between in imidacloprid and thiacloprid, originate the entire discrepancy in bioefficacy of metabolite and its further degrading pathway. These results explain that why thiacloprid is classified as not relevant grade for soil and seed applications, whereas imidacloprid is recommended and acetamiprid is limited.

The main product of the conversion of puerarin by unpermeabilized cells of bacterium Microbacterium oxydans CGMCC 1788 was puerarin-7-O-glucoside (241 +/- 31.9 microM). Permeabilization with 40% ethanol could not increase conversion yield, whereas it resulted in change of main product; a previous trace product became a main product (213 +/- 48.0 microM) which was identified as a novel puerarin-7-O-fructoside by electrospray ionization time-of-flight MS, (13)C NMR, (1)H NMR, and GC-MS analysis of sugar composition, and puerarin-7-O-glucoside became a trace product (14.8 +/- 5.4 microM). However, the extract from cells of M. oxydans CGMCC 1788 permeabilized with ethanol converted puerarin to form 113.9 +/- 27.7 microM puerarin-7-O-glucoside and 187.8 +/- 29.5 microM puerarin-7-O-fructoside under the same conditions. When unpermeabilized intact cells were recovered and used repeatedly for the conversion of puerarin, with increase of reuse times, the yield of puerarin-7-O-glucoside gradually decreased, whereas the yield of puerarin-7-O-fructoside increased gradually in the conversion mixture. The main product of the conversion of puerarin by the tenth recycled unpremerbilized cells was puerarin-7-O-fructoside (288.4 +/- 24.0 microM). Therefore, the change of permeability of cell membrane of bacterium M. oxydans CGMCC 1788 contributed to the change of conversion of the product's composition.

Pollen-mediated gene flow (PMGF) is the main mode of transgene flow in flowering plants. The study of pollen and gene flow of transgenic wheat can help to establish the corresponding strategy for preventing transgene escape and contamination between compatible genotypes in wheat. To investigate the pollen dispersal and gene flow frequency in various directions and distances around the pollen source and detect the association between frequency of transgene flow and pollen density from transgenic wheat, a concentric circle design was adopted to conduct a field experiment using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as the pollen donor and dwarf male-sterile wheat as the pollen receptor. The results showed that the pollen and gene flow of transgenic wheat varied significantly among the different compass sectors. A higher pollen density and gene flow frequency was observed in the downwind SW and W sectors, with average frequencies of transgene flow of 26.37 and 23.69% respectively. The pollen and gene flow of transgenic wheat declined dramatically with increasing distance from its source. Most of the pollen grains concentrated within 5 m and only a few pollen grains were detected beyond 30 m. The percentage of transgene flow was the highest where adjacent to the pollen source, with an average of 48.24% for all eight compass directions at 0 m distance. Transgene flow was reduced to 50% and 95% between 1.61 to 3.15 m, and 10.71 to 20.93 m, respectively. Our results suggest that climate conditions, especially wind direction, may significantly affect pollen dispersal and gene flow of wheat. The isolation-by-distance model is one of the most effective methods for achieving stringent transgene confinement in wheat. The frequency of transgene flow is directly correlated with the relative density of GM pollen grains in air currents, and pollen competition may be a major factor influencing transgene flow.

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