Screening of Soil Streptomycetes – Producers of Antibiotics against Phytopathogenic Bacteria

Abstract

Soil is an inexhaustible source of bacteria of the genus Streptomyces – the producers of the vast majority of known antibiotics that are successfully used in medicine, veterinary and agriculture. The emergence and spread of pathogenic bacteria resistance to antibiotics requires the search for new antibiotic compounds capable of overcoming this problem. Aim. The purpose of this work was to isolate streptomycetes from soil samples of Kyiv and the Kyiv region and study their antibiotic activity against four strains of the different species of phytopathogenic bacteria. Methods. A suspension of soil in distilled water was sown on solid Chapek or corn-soybean medium in Petri dishes, in which trimethoprim and nystatin were introduced to inhibit bacterial and fungal growth. The antibiotic activity of the streptomycetes was tested by setting their agar discs on lawns of phytopathogenic bacteria in Petri dishes. Antibiotics were extracted from the streptomycetes agar cultures with a mixture of chloroform and acetone (2:1), dried in a rotary vacuum evaporator, dissolved in ethanol, separated and purified by thin layer chromatography on aluminum plates (Silica gel 60 F254 from Merck KGaA). The UV/Vis absorption spectra of the antibiotics were measured with a Beckman DU 8 spectrophotometer. Results. 10 strains of streptomycetes were isolated from the soil samples of Kyiv and the Kyiv region, whose antibiotic activity was tested against four phytopathogenic bacteria using the agar block method. Three of the streptomycetes – B8, SK and KZ, formed growth inhibition zones of different phytopathogens on complete medium in Petri dishes, among which the strain SK was the most active. This strain showed antibiotic activity against all four phytopathogenic bacteria – P. syringae 8511, P. carotovorum 8982, C. michiganensis 10 and X. campestris 8003. Conclusions. The results obtained are of interest for the protection of sensitive plants by isolated antibiotics against phytopathogenic bacteria in hothouse conditions.