Chemotaxis of Bacillus cereus YL6 and its colonization of Chinese cabbage seedlings

Background and aims Phosphorus-solubilizing bacteria can colonize the surface of plant roots under natural conditions and may enter plant tissues to form endophytic symbiosis. They can convert unavailable phosphorus in the soil into available phosphorus, which can be utilized by plants. The aims of this study were to investigate the chemotaxis of Bacillus cereus YL6 and its migration and colonization sites in Chinese cabbage and to provide some technical support for the subsequent investigation of the physiological regulation mechanism of phosphate-dissolving bacteria in plants. Methods This study demonstrated that the green fluorescent protein marker did not affect the physiological and biochemical properties of YL6. Through the chemotaxis test and pot experiment, the colonization and growth promoting mechanism of YL6 in Chinese cabbage was explored. Results YL6 showed a strong positive chemotactic response to cabbage roots. The addition of organic acids to the soil promotes the colonization of YL6 in Chinese cabbage roots. Colonization of YL6 in Chinese cabbage is a dynamic process that moves from the root surface to root tissues and then up to stems and leaves. Fluorescence microscopy showed that YL6 mainly colonized cortical cells and vascular bundles of various plant tissues and was also observed in mesophyll cells. The proliferative effect of YL6 resulted from the interaction of effective phosphorus, and exuded auxin and gibberellin in the rhizosheath. Conclusion This study enhanced our understanding of the interaction mechanisms between phosphate-dissolving bacteria YL6 and Chinese cabbage. YL6 has the potential for future development into bio-fertilizer for agricultural production.