Isolation of a Marine Streptomyces mediolani Strain and Its Antimicrobial Activity against Pathogenic Fungi

A total of 22 strains of marine actinomycetes were isolated from seawater,sea mud,offshore soils,marine animals and marine plant samples collected from the sea area near Lianyungang by gradient dilution method.The antimicrobial activity of these strain isolates was tested by plate confrontation method.It was found that 9 of them had antimicrobial activity.Strain ZW-1 had the strongest antimicrobial activity,and it and its fermentation broth possessed strong inhibitory effects on 8 plant pathogenic fungi including Fusarium nivale,Fusarium graminearum,Alternaria alternate,Sclerotinia sclerotiorum,Alternaria solani,Helminthosporium carbonum,Fusarium oxysporum f.sp.niveum,and Fusarium oxysporum f.sp.vasinfectum.In addition to causing cell wall expansion and protoplast contraction in pathogenic fungal mycelia,this strain and its fermentation broth could inhibit the germination of A.solani conidiophores and the elongation of germ tubes.Based on its culture characteristics,morphology,physiological and biochemical properties,and 16S rDNA sequence,ZW-1 strain was identified as Streptomyces mediolani.