Abstract: Soil samples were collected from cotton fields of transgenic cry1Ac + cry2Ab cotton and conventional cotton at each growth stage for analysis of soil bacteria and 16S rDNA gene, using the methods of conventional plate culture, Biolog analysis and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, and impacts of the transgenic cotton on bacterial community structure and functional diversity of soil bacteria have been discussed. Determination of the population of culturable bacteria indicates that the soils in the two cotton fields shared a similar trend in variation of the population of culturable bacteria throughout the entire cotton growth period, and no significant difference existed between the two in total population of soil bacteria, except at the budding stage(P<0.05). Biolog analysis shows that the soil bacteria in the two fields differed significantly in activity and carbon utilization capacity at the seedling and bud stages(P<0.05). Cluster analysis of the PCR-DGGE profiles of the soil bacteria demonstrated that soil bacteria in both fields varied in community structure with growth stage and differed sharply only at the flower and boll stage. PCR-DGGE band sequencing analysis shows that the differences between soil bacteria of the two fields were quite random, which may be attributed to differences in sampling timing and sampling site. To sum up, soil bacteria in the two cotton fields shared a similar trend in variation of community structure and functional diversity throughout the entire growth period, and the impact of transgenic cotton was short and temporary at certain growth stages, and nill during most of the growth period.

Key words: transgenic cry1Ac+cry2Ab cotton, bacterial community structure, functional diversity, PCR-DGGE