Effects Of Two Plants Invasion On The Community Structure Of Bacillus In Soil And Bacillus Feedback Mechanism

The invasion of Ambrosia artemisiifolia L.and Bidens pilosa L.can change the structure of soil microbial community and gather functional bacteria that are beneficial to their own growth,directly or indirectly improve its competitiveness,promote its own growth and inhibit the growth of native plants by changing soil microbial diversity.Bacillus is an important type of rhizosphere growth-promoting bacteria(PGPR)in plant rhizosphere soil,which plays a very important role in promoting plant growth.To explore the relationship between invasive plants and bacillus,we carried out the experiments based the scientific question of“mechanisms of bacillus promoting invasion of exotic compositae”.A.artemisiifolia and B.pilosa was used to study on the impact of their invasion on diversity of bacillus and to identify the bacillus species in the rhizosphere soil.The role of bacillus on the competitive growth of the exotic was discovered.The main results of the study are as follows:Bacillus isolated from the rhizosphere soil of A.artemisiifolia either or S.viridis promoted the biomass of A.artemisiifolia.Besides,and the positive effect of bacillus from the rhizosphere soil of A.artemisiifolia was stronger than that from S.viridis.Bacillus from the rhizosphere soil of A.artemisiifolia enhanced the relative competitiveness of A.artemisiifolia Bacillus in rhizosphere soil of A.artemisifolia had stronger promoting effect on A.artemisifolia.A total of 18 bacillus species were isolated from different soil samples during the invasion of A.artemisiifolia.The diversity of bacillus in the rhizosphere soil of native plants decreased after the invasion of A.artemisiifolia,the bacillus species and its density in the treated soil also changed.Among them,Bacillus megaterium was the dominant species in the rhizosphere soil of A.artemisifolia.In addition,different concentrations of B.megareticus inoculation showed that the addition of B.megaterium significantly promoted the relative competitiveness of A.artemisifolia but inhibited the relative competitiveness of S.viridis in the pot experiment.compared with other treatments,the effect of bacillus inoculation with 15×10~8 cfu/m L and 30×10~8 cfu/m L on the exotic or native growth showed the stronger.A total of 16 bacillus species were isolated from different soil samples during the invasion of B.pilosa.The diversity of bacillus in the rhizosphere soil of native plants and invasive plants decreased after invasion B.pilosa.The species of dominant bacillus also changed in different treatments,and the common dominant bacteria were bacillus A.aryabhattai and B.megaterium.Bacillus isolated from the rhizosphere soil of B.pilosa or from that of S.viridis promoted the biomass of B.pilosa.Meanwhile,the positive effect of bacillus from the rhizosphere soil of B.pilosa was stronger than that from S.viridis Bacillus from the rhizosphere soil of B.pilosa enhanced the relative competitiveness of B.pilosa.Bacillus in rhizosphere soil of B.pilosa showed the stronger positive effect.These results indicated that B.pilosa.promoted its growth by aggregating specific bacillus.Compared to the sterilized soil treatment,the absorption and utilization of nutrient elements B.pilosa were significantly higher in unsterilized soil.The results showed that there was a synergistic relationship between Bacillus and other microorganisms in the rhizosphere soil of B.pilosa,which had a positive effect on its growth.