Alexey Lvovich Stepanov

One hundred and fifty strains of streptomycetes were isolated from grey and dark grey forest soils, as well as from typical chernozem. The isolated strains were analyzed in Vitro for antimicrobial activity on nutrient media and in grey forest soil against twenty-three collection pathogenic test cultures of fungi and bacteria. Four biologically active isolates with a wide spectrum of action were identified and deposited in the All-Russian Collection of industrial microorganisms of the National Research Centre Kurchatov Institute. They were identified and deposited under the following numbers: Streptomyces xiamenensis TB ВКПМ Ас-2204, Streptomyces anulatus TG ВКПМ Ас-2203, Streptomyces sindenensis TK ВКПМ Ас-2205, Streptomyces flavovirens TT ВКПМ АС-2202. A study of the effect of pre-sowing treatment of wheat seeds by the 15-day cultural liquids of the strains S. xiamenensis TB ВКПМ Ac-2204, S. anulatus TG ВКПМ Ac-2203, S. sindenensis TK ВКПМ Ac-2205 on germination rates and infection with F. graminearum revealed that they inhibited the growth of a pathogenic fungus. Besides, they improved seed vigour and germination of wheat. The resulting strains of soil actinomycetes can be used in biotechnology with an aim to create the new bioinoculants when dealing with phytopathogenic bacteria and fungi. The strains can also be used for stimulating the plant growth, as well as for soil bioremediation in organic farming. Through the application of the HPLC method, specialized antimicrobial metabolites of monosporic strain suspensions were identified. 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), 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 introduced actinobacteria under study in soil samples showed high activity of streptomycetes that use chitin. Analysis of the diversity of the prokaryotic complex of the studied soil samples with the application of the high-throughput sequencing of the conserved region of the 16S rRNA gene method revealed during the introduction of S. xiamenensis TB ВКПМ Ac-2204 that its controlling role in the microbial community is due to its antibiotic-forming activity.

The paper presents the results of assessing the eff ect of the degree of soil erodibility on the abundance and diversity of cultivated fungi and actinomycetes in diff erent seasons of the annual cycle. The objects of the study are sod—podzolic soils (Umbric Retisols (Abruptic)) of diff erent degrees of washout, located on the slope of the southeastern exposure (Moscow region, Solnechnogorsk district), used for a long time for the cultivation of agricultural crops. The indicators of microbial abundance were determined by the cup method, identifi cation was carried out on the basis of phenotypic characters. It is shown that the decline in physical and agrochemical parameters of the soil, which is a result of erosion processes, leads to a change in microbiological parameters. A decrease in the abundance and species diversity of fungi and actinomycetes was found with an increase in the degree of soil erosion. Significant diff erences were found in the taxonomic composition of microbial communities of non-eroded and washed away soils (the Sorensen species similarity coeffi cient does not exceed 0.42 for fungi and 0.30 for actinomycetes). Taxonomic units of mycelial microorganisms have been identifi ed. Among the fungi are representatives of the species Aspergillus, Cladosporium and Scopulariopsis, among the actinomycetes are Streptomyces malachitospinus, S. candidus and Micromonospora aurantiaca.