| Potato common scab caused by Streptomyces spp.is a severe disease affecting potato production worldwide.There is still a lack of effective control measures.Biological control is a key measure to control this disease.In our early study,PBSH9 was highly effective for controlling potato common scab(S.galilaeu).Disease control was up to 73.97%in field trials,and increasing yield and tuber quality of potato.It was preliminarily identified as a novel Streptomyces sp.by morphological,physiological and biochemical analysis,16S rDNA and multi-site sequence analysis(MLSA).In this experiment,we want to further compare with the model strain for identification of strain PBSH9.At the same time,the antimicrobial activity of strain PBSH9 against potato common scab caused S.galilaeu will be studied and the antimicrobial substances will be isolated.1.The whole genome sequence of the biodefense strain PBSH9 was examined using the Nanopore sequencing platform,and the results showed that the genome size of strain PBSH9was 7,347,225 bp,with 131,027 reads obtained with an average length of 11,868 bp and G+C content of 71.65%,and the protein-coding genes,rRNA genes and tRNA genes in the genome were 6,473,18 and 71 genes respectively.The anti SMASH v6.0.1 web-based analysis platform was used to derive,31 secondary metabolite biosynthesis gene clusters of18 types,and 25 possible active compounds were predicted,no compounds were found to have inhibitory effects on the pathogenic Streptomyces.2.The average nucleotide identity(ANI)and digital DNA-DNA hybridization(d DDH)values of strain PBSH9 were 95%and 70%lower than the inter-species critical values,the MLSA was greater than 0.007.Strain PBSH9 was identified as a new species and named as Streptomyces hohhotensis sp.nov.(JAKZEO00000000000).3.The optimal culture conditions of bioactive metabolites on strain PBSH9 showed that100 m L of HBERC-17 medium inoculated with 9 m L of seed solution(1×10~8 CFU/m L)at pH 7,28℃ and for 5 days were the best inhibition against S.galilaeu.HBERC-17 medium was selected as the bulk fermentation medium.4.Two antibacterial compounds were obtained from the metabolites of strain PBSH9 using silicagel column chromatography and Pre-HPLC.5.The biological activity showed that the minimum inhibitory concentration(MIC)of compound 1 and compound 2 were 0.977μg/m L and 1.953μg/m L,respectively.S.galilaeus were significantly inhibited,and the inhibitory effect of compound 1 was higher than that of compound 2 at the minimum inhibitory concentrations.Compound 1 and compound 2 could inhibit the S.galilaeus and reduce the damage to potato chips and radish seedlings,when the concentration was high,it was toxic to potato tissue and radish seedlings.6.Compound 1 and compound 2 were stable in neutral environment,while both acidic and alkaline conditions degraded the content.Two compounds were stable which treated from 0.5 to 3 h at 4,10,20,30 and 40℃.After treatment at 50℃ for 0.5 h,two compounds were stable.And the thermal stability of the two compounds was poor more than 0.5 h. |
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