Identification of Endophytic Bacterium CIII-1 Strain from Mangrove and Isolation of its Antimicrobial Proteins

Abstract:

The CⅢ-1 strain, a marine bacterium screened out from 422 endophytic bacteria isolated from mangroves by the method of plate test, strongly inhibited the growth of Ralstonia solanacearum, Staphylococcus aureus, Vibrio alginolyticus, Phytophthora capsici, Fusarium oxysporum f. sp. cubense, etc. It was identified as Bacillus amyloliquefaciens based on the characters of morphology, physiology and biochemistry and 16S rRNA. Antimicrobial protein which produced by CIII-1 was the main antibacterial substance. The crude protein in culture filtrate could be precipitated with 33% ammonium sulfate and obtained by dialysis of the precipitate. The protein was found to be thermal-unstable, when treated at 60?C and 100?C for 10 minutes, its inhibitive activity would lost 62.5% and 100% respectively. The inhibitory activity of the protein was observed in the range of pH value from 5.0 to 10.0, and the strongest one was at pH 7.0.