Effects of Microbial Fertilizers on Microbial Community Structure in RadixpseudostellariaeRhizosphere

In order to study the changes in microbial community structure and functional diversity in rhizosphere soil,five soil samples were used as experimental materials in this paper.Biolog results indicated that there was a significant change in the catabolic diversity in response to microbial fertilizer treatments.There was a highest metabolic activity in utilizing carbon in the newly planted soil.Compared to the second year-monoculture soil and Bacillus amyloliquefaciens-treated soil(treatment 3),the metabolic activities of 6kinds of carbon were lower in microbial fertilizers-treated soils(treatments 1and 2).PLFA results showed that 27 kinds of PLFA biomarkers were extracted from five soil samples.The group-specific PLFAs in five soil samples showed the same trend that gram-positive bacteria(G +)>fungi> gram-negative bacteria(G-)> bacteria > actinomycete.Compared to the second year-monoculture soil and Bacillus amyloliquefaciens-treated soil,,the contents of these group-specific PLFAswere significantly lower inmicrobial fertilizers-treated soils(treatments 1and 2).The variability in the PLFA profiles was consistent with the changes in BIOLOGfingerprinting.Moreover,the ratio of cyclopropyl PLFAs to their metabolic precursors(cy/pre)was greatly higher in the second year-monoculture soil and Bacillus amyloliquef aciens-treated soil than in the microbial fertilizers-treated soils,implying higher physiological stresses in microbial communities in the consecutively monocultured soils.In conclusion,Radix pseudostellariae monoculture and microbial fertilizer treatments had great effects on the microbial community structure and functional diversity.It suggested that the imbalance in soil microbial community was one of the main reasons for consecutive monoculture problems of Radix pseudostellariae.