Algicidal Activity and Action Mode of Streptomyces flavogriseus MK17 Metabolites on Cyanobacteria

The results of a study on the algicidal activity of a crude extract of metabolites of MK17 isolated from the biomass of the soil actinobacterium Streptomyces flavogriseus MK17, as well as the mechanisms of its stress effects on cyanobacteria, are presented. The MK17 metabolites exhibit algicidal activity against cyanobacteria and green algae, with cyanobacteria being more sensitive to their effects than green algae. It is found that exposure to the crude MK17 metabolites leads to a decrease in the concentration of microcystins produced by the toxigenic cyanobacteria Microcystis aeruginosa and Planktothrix agardhii. The MK17 metabolites were shown to impair the functioning of the cyanobacterial photosystem. The increased generation of reactive oxygen species in the cells, along with elevated levels of malondialdehyde and activation of antioxidant defense mechanisms, indicate the development of oxidative stress in cyanobacterial cells under the influence of the MK17 metabolites.