CHARACTERISTIC OF STREPTOMYCES SPECIES WITH ANTIMICROBIAL ACTIVITY AGAINST SELECTED PHYTOPATHOGENIC BACTERIA AND FUNGI

Abstract

The object of this study was to find and characterise streptomycete isolates with antimicrobial activity accomplished by the agar plug method against phytopathogenic species. The test-microorganisms were selected according to their importance in agriculture. All of them belong to phytopathogenic species which reduce yields of agriculturally important plants worldwide. A total number of four phytopathogenic bacteria (Xanthomonas campestris (CCM 22), Pseudomonas syringae (CCM 2868), Erwinia amylovora (CCM 1114), Clavibacter michiganensis subsp. sepedonicus (CCM 7014)) and four phytopathogenic fungi (Botrytis cinerea, Fusarium poae, Alternaria tenuissima, Alternaria arborescens) were used for this experiment. Overall twenty streptomycete isolates showed antimicrobial activity against at least two of the test-microorganisms. These active isolates were subsequently characterized. Streptomycete isolates were observed for morphological characteristics, such as morphology and colour of aerial and substrate mycelium, colour of diffusible pigments, production of melanoid pigments on peptone-yeast extract iron agar and sporophore and spore chain morphology following the International Streptomyces Project. Genes coding polyketide synthase (PKS-I) and nonribosomal peptide synthetase (NRPS), which are considered to responsible for the synthesis of large number of biologically active compounds, like antibiotics and antifungals, that are produced by Streptomyces species largely, were screened. The occurrence of these genes in the genome of our isolates was in accordance with results from antimicrobial activity analysis. Classification to genus Streptomyces were confirmed by DNA sequencing.