Antimicrobial Activity of Specialized Metabolites of Soil Chitinolytic Streptomycetes

Abstract

One-hundred-and-fifty strains of streptomycetes have been isolated from gray and dark gray forest soils, as well as from typical chernozem. The isolated strains were analyzed in vitro for antimicrobial activity on nutrient media and in gray forest soil against 23 collection pathogenic test cultures of fungi and bacteria. Four biologically active isolates with a wide action spectrum have been identified and deposited at the All-Russia Collection of Industrial Microorganisms of the National Research Center “Kurchatov Institute” under the following numbers: Streptomyces xiamenensis TB VKPM As-2204, Streptomyces anulatus TG VKPM As-2203, Streptomyces sindenensis TK VKPM As-2205, and Streptomyces flavovirens TT VKPM As-2202. A study of the effect of presowing treatment of wheat seeds with 15-day culture liquids of S. xiamenensis TB VKPM As-2204, S. anulatus TG VKPM As-2203, and S. sindenensis TK VKPM As-2205 for germination rates and levels of infection with F. graminearum has revealed that they inhibited the growth of a pathogenic fungus and improved the seed vigor and germination of wheat. The resulting strains of soil actinomycetes can be used in biotechnology for creating new bioinoculants to combat phytopathogenic bacteria and fungi. The strains can also be used for stimulating the plant growth, as well as for soil bioremediation in organic farming. Based on the HPLC method (high-performance liquid chromatography), we have identified specialized antimicrobial metabolites of monosporous strain suspensions. The identified antibiotics are N-Butylbenzenesulfonamide, 1-(1H-Benzo[d]imidazol-2-yl)ethan-1-ol, 2-[(3S)-1-(Cyclohexylmethyl)-3-pyrrolidinyl]-1H-benzimidazole-5-carbonitrile, Cyclo(leucylprolyl), and Cyclo(phenylalanyl-prolyl). The identified antiseptics are Cetrimonium and Carvone. The identified phytohormone is auxin indole-3-acetic acid (IAA). Observation of the dynamics of development of the introduced actinobacteria in soil samples has shown a high activity of streptomycetes that use chitin. Analysis of the diversity of the prokaryotic complex of the studied soil samples based on high-throughput sequencing of the conserved region of the 16S rRNA gene has revealed its controlling role in the microbial community during the introduction of S. xiamenensis TB VKPM As-2204, which is determined by its antibiotic-forming activity.