Study On Broad-spectrum Antifungal Activity Small Molecules And Antifungal Proteins Of Streptomyces Albidoflavus HKIB0005

As an significant source of active natural products,microorganisms have played an important role in the development of medicine and pesticides.At present,most antimicrobials are microbial products and their derivatives.Among them,Actinomycetes,as the main source of antimicrobials,has always been a resource bank of active natural products.and metabolites are widely used in daily life and agricultural production.However,previous studies mainly focused on small molecules with antimicrobial activity of Actinomycetes,with relatively less attention paid to antimicrobial peptides and antimicrobial proteins.In this study,53 strains of antimicrobial active actinomycetes were screened from the actinomycetes isolated from samples collected at high altitude.During the preliminary screening of antibacterial activity of these active strains,a number of small molecular antimicrobial substances were found,including polyene,antimycins,alkaloids,macrolides and other structural types.At the same time,it was also found that Actinomycetes Streptomyces sp.HKIB0005 could express and produce broad-spectrum antifungal proteins under certain culture conditions.Through further isolation and purification,sequencing and whole genome analysis,it was found that the antifungal protein was an unreported type of antifungal protein--dehydrogenase.It was identified that the size of the dehydrogenase was about 43 k Da and the expression level was as high as 0.3mg/m L.Antifungal activity showed that HKIB0005 fermentation broth could completely inhibit or kill Magnaporthe grisea without dilution.The fermentation broth still had significant antifungal activity after 100 times dilution;the inhibition rates against Phytophthora capsici,Fusarium oxysporum and Trichothecium roseum were 60%,40%and 50%,respectively.The determination of physical and chemical parameters showed that the dehydrogenase was gradually inactivated when the temperature was higher than 80℃.Cr³⁺could completely inhibit the activity of protein and showed stability to protease K.It is found that the mature form of the dehydrogenase with antifungal activity is about43 k Da and the immature form is about 49 k Da.The specific antimicrobial mechanism and post-maturation mechanism of the dehydrogenase need to be further studied.The dehydrogenase has excellent broad-spectrum antifungal activity and stability,which makes it a potential antifungal biological control protein.