An algicidal Streptomyces amritsarensis strain against Microcystis aeruginosa strongly inhibits microcystin synthesis simultaneously.

Microcystis aeruginosa and hepatotoxic microcystins produced by it have posed a severe threat to aquatic ecological security and human health. In this study a Streptomyces amritsarensis HG-16, showing high algicidal activity against M. aeruginosa and strong inhibitory effect on microcystin synthesis, was obtained by screening some anti-Fusarium sp. microbial strains isolated before in our laboratory. HG-16 bound cyanobacterial cells by mycelia to form flocs and killed M. aeruginosa by secreting active substances, which were proteinase K resistant and stable in the temperature range of 35–75 °C and pH range of 3–11. HG-16 removed M. aeruginosa of 105 and 106 cell mL−1 cell densities in similar rate and was active against all the tested harmful unicellular and filamentous cyanobacteria. Results of differential gene expression analysis indicated that HG-16 affected the photosynthesis system and microcystin synthesis of M. aeruginosa. Accordingly, the algicidal activity of HG-16 was light-dependent, and microcystin synthesis of M. aeruginosa decreased by 91.2% with HG-16 treatment. Thus, it is promising to utilize HG-16 to mitigate harmful cyanobacterial blooms, inhibit microcystin synthesis and control plant disease caused by Fusarium.spp. through irrigating farmland with eutrophic water applied HG-16.