Endophytic Bacillus altitudinis Q7 from Ginkgo biloba inhibits the growth of Alternaria alternata in vitro and its inhibition mode of action

Abstract

The study was focussed on the inhibitory mechanism associated with the ability of an endophytic bacterium - Bacillus altitudinis Q7, obtained from Ginkgo biloba, to inhibit the growth of Alternaria alternata in vitro. A fungus, identified as Alternaria alternata was isolated from the rotten part of an apple. One of the endophytes was identified as Bacillus altitudinis Q7. Effect of Bacillus altitudinis Q7 on Alternaria alternata was characterized by measuring membrane permeability and lipid peroxidation. Antioxidant enzymes in Alternaria alternata were determined before and after exposure to Bacillus altitudinis Q7. Results indicated that cell membranes in Alternaria alternata were damaged, lipid peroxidation was enhanced, and superoxide dismutase, peroxidase, and polyphenol oxidase were significantly inhibited. Content of lipopeptides produced by Bacillus altitudinis Q7 was higher than other metabolites. The FTIR spectra revealed that the prepared antibacterial lipopeptides is a cyclic lipopeptides. The effect of lipopeptides produced by Bacillus altitudinis Q7 at 2 mg/mL against Alternaria alternata in vitro reached 83.2%. The lipopeptide-treated group showed the same trend as Q7 fermentation broth in inhibition mode of action. Moreover, the utilization of proteins and sugars during culturing of Alternaria alternata decreased when adding lipopeptides to the growth medium. Bacillus altitudinis Q7 from Ginkgo biloba significantly inhibited the growth of Alternaria alternata and is a very promising biocontrol strain against Alternaria alternata. The study of endophytic bacteria and its metabolites is being done to identify biological control alternatives. The results provide a theoretical basis for understanding their antagonistic properties.