Loss Of Gltb Inhibits Biofilm Formation And Biocontrol Efficiency Of Bacillus Subtilis Bs916 By Altering The Production Of Gamma-Polyglutamate And Three Lipopeptides

AimsThis study examined the contribution of GltB on biofilm formation and biocontrol efficiency of B. subtilis Bs916.Methods and ResultsThe gltB gene was identified through a biofilm phenotype screen and a bioinformatics analysis of serious biofilm formation defects, and then a gltB single knockout mutant was constructed using homologous recombination. This mutant demonstrated severe deficits in biofilm formation and colonisation along with significantly altered production of.-polyglutamate (gamma-PGA) and three lipopeptide antibiotics (LPs) as measured by a transcriptional analysis of both the wild type B. subtilis Bs916 and the gltB mutant. Consequently, the mutant strain retained almost no antifungal activity against Rhizoctonia solani and exhibited decreased biocontrol efficiency against rice sheath blight. Very few gltB mutant cells colonised the rice stem, and they exhibited no significant nutrient chemotaxis compared to the wild type B. subtilis Bs916. The mechanism underlying these deficits in the gltB mutant appears to be decreased significantly in production of gamma-PGA and a reduction in the production of both bacillomycin L and fengycin. Biofilm restoration of gltB mutant by addition gamma-PGA in the EM medium demonstrated that biofilm formation was able to restore significantly at 20 g/L.ConclusionsGltB regulates biofilm formation by altering the production of gamma-PGA, the LPs bacillomycin L and fengcin and influences bacterial colonisation on the rice stem, which consequently leads to poor biocontrol efficiency against rice sheath blight.Significance and Impact of StudyThis is the first report of a key regulatory protein (GltB) that is involved in biofilm regulation and its regulation mechanism and biocontrol efficiency by B. subtilis.