Effects of two Bacillus spp. strains on the growth of peanut seedling and microbial community structure in rhizosphere soil

Abstract:

[Background] The growth-promoting effects and mechanisms of Bacillus velezensis and Bacillus firmus on peanut seedlings have not been reported. [Objective] This study comprehensively explored the growth-promoting mechanism of two Bacillus strains on peanut by analyzing of rhizosphere microbial community and soil available nutrients, including nitrogen, phosphorus and potassium. [Methods] two strains (named as Bacillus velezensis HP9, Bacillus firmus HP10) were irrigated-root alone, or mixed on peanut seedling by pot experiment, their effects on peanut’s growth and available nutrients of rhizosphere soil were assessed. The community structure and diversity of bacteria and fungi in rhizosphere soil, including irrigated-root groups and control group, were analyzed by high-throughput sequencing technology, too. [Results] Comparing to control group, stem length and fresh weight of treated peanuts were obviously increased; in rhizosphere soil, alkali-hydrolyzed nitrogen contents was improved greatly, available phosphorus and potassium contents were also increased differently. When Bacillus strains were irrigated with peanut seedlings, there were no significant influence on microbial diversity of rhizosphere soil, but microbial community structure, including bacteria and fungi, were affected. At the phylum level, the relative abundance of Bacteroidetes and Mortierellomycota increased significantly in three treated groups. relative abundance of these genus, such as Agrobacterium, Arthrobacter, Bacillus, Burkholderia, Flavobacterium, Pedobacter, Polaromonas, Pseudomonas, Sphingomonas, Stenotrophomonas, were significantly improved; and six bacterial genus, including Achromobacter, Brevundimonas, Chryseobacterium, Ochrobactrum, Sphingobacterium and Sphingopyxis, were only detected in three treated groups. Using the method of principal component analysis, community structure of rhizosphere soil were found more similar in treated groups than the control. [Conclusion] Bacillus velezensis HP9 and Bacillus firmus HP10 could influence microbial community structure and increase the relative abundance of functional flora in rhizosphere soil, thus the soil fertility was improved and the growth of peanut seedling was promoted, too.