RESUMO
By using T-RFLP approach, this paper studied the dynamic changes of bacterial community in the rhizosphere soils under continuously planting burley tobacco for 1, 2 and 4 years. With the increasing of continuous planting years, the Shannon index and Margalef index of bacterial community in the rhizosphere soils decreased after an initial increase. After 4-year continuous planting, the diversity of the bacterial community decreased significantly, and the community structure became simple. The similarity coefficient of the bacterial community in the rhizosphere soils of continuously planting burley tobacco for 1 and 2 years and of the control was decreased with increasing year of continuous planting. Actinobacteria were predominant in the soils under 1 and 2 years continuous planting and in the control, but decreased in the soil continuously planted with burley tobacco for 4 years, in which, Bacilli of Firmicute was the dominant. It was suggested that continuously planting burley tobacco could result in the decrease of beneficial microbes such as Sphingomonas and Streptomyces while increase the species of pathogenic bacteria such as Bacillus cereus in rhizosphere soil, which in return, could lead to the imbalance of bacterial community and deteriorate the micro-ecological conditions in rhizosphere soil.