Correlation Of Root Exudates Components And Gene Transcription Of SQR9 And Its Effects On Chemotaxis And Biofilm Formation

Rhizosphere colonization capacity of rhizospheric micoorganisms is depended on both its own characters and plant root exudate components.Plant root exudates act not only as carbon sources to supply energy for soil microbes,but also as signals to regulate soil microbial communities.Previous study has identified the transcriptiomic differences of Bacillus amyloliquefaciens SQR9 in response to the root exudates of cucumber,maize and banana using high-throughput Solexa sequencing.In the present study,root exudates of cucumber,maize,and banana were collected and analyzed by GC-MS.Correlation of root exudates components and gene transcription of SQR9 revealed the corresponding relationships between each other and can be used to guide further experiments regarding to chemotaxis and biofilm formation.The main results were summarized as follows:1.GC-MS analyses of cucumber,maize,and banana root exudates showed that 176 compounds were detected and 111 compounds were further identified referred to the database,with the 65 compounds were unclassified.Analysis of the distribution of each component in different root exudates indicated that all the 176 compounds can be detected in those three root exudates,but the relative abundance of each component was largely different.For instance,the amides in cucumber root exudates,sugar alcohols in maize root exudates,and amines in banana root exudates were occupied 20%of the total abundance,respectively.2.Correlation analyses of gene transcriptome of SQR9 and metabolome of cucumber,maize,and banana revealed that acetophenone,hydroxylamine,glycerin-stearic acid and plamitic acid monoglyceride were positively correlated with the genes associated with bacterial movement,chemotaxis,and extracellular polysaccharide.All the three root exudates can enhance the biofilm formation of SQR9 and the maize root exudates had the greatest enhancement in biofilm formation,which suggested that it might be due to the high abundance of erythritol in maize root exudates.3.Cucumber,maize,and banana root exudates were concentrated to I mg/mL and the organic acids and phenolic acids in these root exudates were identified by HPLC.Oxalic acid,malic acid,citric acid,succinic acid,fumaric acid,hydroxybenzoic acid,vanillic acid,ferulic acid,and cinnamic acid were detected and they all can promote the biofilm formation of SQR9,with different optimal concentrations.11 amino acids,6 phenoic acids,and 5 organic acids were selected based on the GC-MS results and used to evaluate the effects of these compounds on chemotaxis.Results showed that malic acid,citric acid,fumaric acid,cinnamic acid,ferulic acid,p-hydroxy benzoic acid,proline,leucine and glycine had a significant chemotaxis.