The Safety Of BS-Z15 Crude Metabolites Against Verticillium Dahliae

BS-Z15 is a Bacillus subtilis isolated and purified independently by our laboratory,which has a good inhibitory effect on the growth of Verticillium dahliae,the pathogen of Verticillium wilt of cotton.It has been proved that its strains and metabolic active substances have a good control effect on Verticillium wilt of cotton under laboratory conditions.Whether the metabolites of BS-Z15 can be used as biological agents or not is of great significance to evaluate the safety of BS-Z15 against Verticillium dahliae.In this paper,BS-Z15 was selected to extract crude metabolites active substances,and its effects on plants,animals and soil microorganisms were studied.The biosafety of the crude metabolites was analyzed comprehensively.The results are as follows:(1)The results of solid medium and soil culture showed that the crude metabolites of BS-Z15 could promote the growth of Arabidopsis thaliana at low concentration and inhibit the growth at high concentration.A certain concentration of crude metabolites could promote the growth of Arabidopsis thaliana and advance the flowering period of Arabidopsis.Under hydroponic conditions,high concentration of BS-Z15 crude extract(containing 0.33 mg/m L of antimicrobial substance,which is directly expressed as mg/m L below)also inhibited the growth and photosynthetic characteristics of cotton plants,but delayed treatment or removal of BS-Z15 crude extract metabolite after a period of time could make cotton plants grow normally.(2)The mice were treated with 32.67 mg/kg crude extract metabolites by intragastric administration for 60 days without toxic symptoms,and the mortality rate decreased.There was no significant effect on the organ index,heart and liver tissue characteristics of mice,and the activity of antioxidant enzymes in liver tissue was significantly increased.The content of MDA in liver showed a significant downward trend.(3)Sequencing of the ITS1 region of fungi in soil samples showed that crude extraction of metabolites by BS-Z15 could improve the richness and diversity of fungal communities in soil.The relative abundance of Ascomycota increased after the treatment of soil with BS-Z15 crude extract metabolites.The relative abundance of Mortierellomycota and Mortierella both increased at the initial stage of treatment,but had little effect at the later stage of treatment.The metabolites of BS-Z15 at the later stage of treatment could improve the relative abundance of Tricharina.The abundance of pathogenic fungi with relative abundance greater than 1% in soil decreased,and the abundance of saprophytic fungi had little effect on the whole.(4)Sequencing analysis of 16 S r DNA(V3+V4)region of bacterial in soil samples showed that BS-Z15 metabolites had no significant effect on the richness and diversity of bacterial communities in soil.After treatment with BS-Z15 metabolite,the relative abundance of Proteus increased slightly,but had little effect on the relative abundance of other main phylums.At generic level,the relative abundance of Pseudomonas increased slightly,but had little effect on the relative abundance of other major genera.In conclusion,the analysis of the treatment of plant,animal and soil microecology by BS-Z15 crude extract of metabolites showed that the metabolites should be safe and harmless,and could be further developed and utilized.It also showed that low concentration promoted the growth of plants and reduced the abundance of harmful fungi in soil,which laid a theoretical foundation for the subsequent development and utilization of the metabolite.