Abstract:

【Objective】 Bacillus altitudinis LZP02 is a plant growth-promoting rhizobacteria（PGPR）in the rice rhizosphere, which can colonize rice rhizosphere to form biofilm, and Mn²⁺ can promote the biofilm formation of LZP02 strain, but the regulation mechanism is not clear. The purpose of this study is to explore the mechanism of Mn²⁺ promoting the biofilm formation of LZP02 strain. 【Method】 Crystal violet staining and anthrone-sulfuric acid method were used to perform quantitative analysis of biofilm and exopolysaccharide yield, respectively. Scanning electron microscope（SEM）was used to observe LZP02 colonization in rice rhizosphere. And differently expression genes（DEGs）were analyzed by transcriptome sequencing technology.【Result】 The addition of 4 mmol/L Mn²⁺ and 8 mmol/L Mn²⁺ significantly enhanced the film-forming ability of LZP02 strain and the production of exopolysaccharide, scanning electron microscopy showed that 4 mmol/L Mn²⁺ and 8 mmol/L Mn²⁺ improved the colonization ability of LZP02 strain in rice rhizosphere. The number of DEGs increased significantly with the increase of Mn²⁺ concentration, which was mainly enriched in spore formation, toxin metabolism pathway and two-component system. The expression of skf operon gene was up-regulated in 1 mmol/L Mn²⁺ and 4 mmol/L Mn²⁺ treatments. Scanning electron microscope observation showed that there was damage in LZP02 cells in 1 mmol/L Mn²⁺ and 4 mmol/L Mn²⁺ treatments. The genes of KinE and Spo0A in the two-component system of 4 mmol/L Mn²⁺treatment group were significantly up-regulated. 【Conclusion】 Mn²⁺ can improve the biofilm-forming ability of strain LZP02 by “cannibalism” and KinE gene activates Spo0A~P in two-component system.

Key words: Bacillus altitudinis LZP02, biological film, Mn²⁺