Abstract: Peganum harmala L.is strong in resistance against severe environment,such as drought and low temperature.Plants play an important role in maintaining the local ecological environment.In order to understand the mechanism of ecological adaptation and interaction with environment,the characteristics of bacterial communities in rhizosphere soil of P.harmala in a desert steppe in Baiyin,Gansu Province were studied using the high-throughput sequencing and culture-dependent method,and they were compared with those of surrounding soil.The results showed that the bacterial communities in the rhizosphere soil were consisted of 30.01% Actinobacteria,23.98% Proteobacteria,11.53% Bacteroidetes and 10.19% Acidobacteria.The dominant soil bacterial community in the surrounding desert steppe was composed of 55.05% Actinobacteria,21.11% Proteobacteria and 6.07% Acidobacteria.The cultivable bacterium group included Firmicutes,Proteobacteria and Actinobacteria.In the rhizosphere soil,the dominant bacteria were 23.53% Brevibacterium, 23.53% Bacillus,17.65% Pseudomonas and 11.76% Brevundimonas. The dominant populations of bacteria in the surrounding soil were 37.50% Arthrobacter, 18.75% Bacillus and 12.50% Pseudomonas. The difference of bacterial communities between the rhizosphere soil of P.harmala and its surrounding desert steppe soil was significant.The bacteria numbers and diversity index in the rhizosphere soil were significantly higher than those of the surrounding desert steppe soil.The results provided the scientific basis for exploring the interaction between the desert steppe plants and their rhizobacteria,and also for understanding the roles of the rhizobacteria in promoting plant growth and soil material transformation.

Key words: desert steppe, Peganum harmala L., rhizosphere soil, bacterial community, high throughput sequencing, soil microorganism