Biofilm formation and antagonistic ability of Bacillus amyloliquefaciens JK-JS8 under Zn stress

Abstract:

[Background] Zinc (Zn) is an important trace element for the structure and regulatory system of bacterial cells. In the environment, bacteria exposed to high levels of Zn ions can be affected on their functions.[Objective] To study the effect of Zn on Bacillus amyloliquefaciens JK-JS8 biofilms and its antagonistic ability against Sphaeropsis sapinea, and to explore the possible mechanism between them, so as to provide theoretical basis for the application of biocontrol bacteria in different environmental conditions.[Methods] The formation of B. amyloliquefaciens JK-JS8 biofilms under different concentrations of Zn ions was observed, and the effect of non-lethal concentration of Zn on the antagonistic ability of B. amyloliquefaciens JK-JS8 against S. sapinea was explored by the plate confrontation method. Quantitative reverse transcription-polymerase chain reaction (RT-qPCR) was used to detect the expression of biofilm-related genes and the generation of antibacterial products after the treatment of ZnCl₂.[Results] The concentration of Zn ions at 300 μmol/L had no effect on the growth of B. amyloliquefaciens JK-JS8, but significantly inhibited the formation of its biofilms and the antagonism against pathogenic organisms. Under Zn stress, the expression levels of biofilm-related genes such as tasA, spo0A and bamD were markedly down-regulated compared with the conditions in control group. The production of bacillomycin D decreased by 39.1%, 58.8% and 61.0% at 24 h, 48 h and 72 h, respectively, which was determined by the liquid chromatography. [Conclusion] High concentration of Zn ions in the environment can affect the formation of B. amyloliquefaciens JK-JS8 biofilms and reduce its ability to antagonize the pathogenic organisms.