Actinomycete Complexes in Eutrophic Peatlands

The actinomycete complexes of eutrophic peatlands differing by genesis were studied in order to broaden the knowledge of microorganisms’ biodiversity in wetland ecosystems and to detect microorganisms with a high potential for antagonistic action. The research sites included eutrophic peatlands of lacustrine, forest, and floodplain origins in Tver and Tomsk regions, Russia. Samples from the 3-m-thick peatlands were taken layer-by-layer with due account for the botanical composition of peat in September 2019. The length and biomass of the mycelium of actinomycetes were determined by luminescent microscopy; and the number of culturable actinomycetes was determined by plate method. The actinomycetes species were identified by their morphological and cultural features and the analysis of 16S rRNA fragments. The antagonistic activity of streptomycetes was analyzed by the method of agar blocks. The actinomycetic mycelium was found throughout the peatland profiles. Its length varied from 700 to 3000 m/g dry peat and its biomass was from 22 to 140 mg/g dry peat. A reliable correlation between the abundance of actinomycetic mycelium and the botanical composition of peat was determined for the first time. It was also found that the abundance of actinomycetic mycelium depends on the degree of decomposition of profile-forming peat. The actinomycete complex included representatives of the Streptomyces , Micromonospora , Streptosporangium , and Streptoverticillium genera. Representatives of Streptomyces were dominant according to their occurrence frequency and were assigned to 19 species from 9 series and 5 sections. About 70% of the studied actinomycetes demonstrated the ability for microaerophilic growth. This fact indicated that these actinomycetes are adapted to the oxygen deficiency in the deep layers of peatlands. Antibacterial activity was found in 89% of the isolates. S. avicenniae and S. caeruleus proved to be the most active strains with antibacterial activity and multiple resistance to antibiotics.