Effects Of Microcystis Aeruginosa On Microbial Community Structure And Function In Water

Lake Taihu is a large shallow lake in the Yangtze River Delta of China.Since the 1980 s,Microcystis spp.has been an important part of Lake Taihu.The frequency and intensity of cyanobacterial outbreaks are increasing worldwide.The outbreak of cyanobacteria can cause a series of serious water and social problems.When blooms in natural waters,it is mostly cyanobacterial blooms,and Microcystis aeruginosa is the most common one.Interactions between toxic cyanobacteria and aquatic microorganisms need to be critically evaluated to understand microbial drivers and modulators of the outbreaks.In this study,we applied 16S/18 S rRNA gene sequencing and metabolomics analyses to measure the microbial community composition and metabolic responses of M.aeruginosa in microcosm coculture system receiving dissolved inorganic nitrogen and phosphorus(DIP)close to the average concentrations in Lake Taihu.In the coculture system DIP is depleted,and growth and production of aquatic microorganisms can be stressed by DIP availability,while M.aeruginosa could accelerate its growth by not only inducing the activity of alkaline phosphatase to hydrolyze organic phosphorus secreting from aquatic microorganisms,but also upregulating energy metabolism-related pathways(glycolysis,pentose phosphate pathway,tricarboxylic acid cycle,sugar metabolism,and glycerol metabolism).Furthermore,M.aeruginosa can decrease carbohydrate metabolism of aquatic microorganisms by inhibiting glycolysis,tricarboxylic acid cycle and sugar metabolism pathways and thus disrupt original microbial activities,and this had a negative effect on bacterial and eukaryotic microbial richness and the diversity.Microcystin were capable of decreasing the biomass of total phytoplankton in aquatic microcosms.Overall,compared with the monoculture,the growth of M.aeruginosa in the coculture system is faster,but the growth of total aquatic microorganisms(Bacteroidete,Cryptomycota and many rare microorganisms with a relative abundance of less than 1%)is inhibited with the diversity and richness of eukaryotic microorganisms being more negatively impacted than prokaryotic microorganisms.According to our research,M.aeruginosa is the main cyanobacterial species in the occurrence of cyanobacterial blooms in Lake Taihu.The occurrence of cyanobacterial blooms must have strong impacts on microorganisms.Therefore,this study has a guiding significance for exploring the interaction between toxic cyanobacteria(M.aeruginosa)and microorganisms.