Microbial regulation of Microcystis colony formation: Mechanisms driving bloom persistence and toxicity

Colony formation is essential for cyanobacterial bloom in aquatic environment. As the most widespread organism in water bodies, the role of microorganisms on the formation of colonies is still unclear. This study reported that the aquatic microorganisms could promote the aggregation behavior of Microcystis cells in two ways: first, through the accumulation of biomass, and second, by causing Microcystis cells to aggregate and not separate. The aquatic microorganisms alleviated the environmental stress and promoted the growth of Microcystis cells. The algal cells and aquatic microorganisms aggregated and secreted more extracellular polymers for ecological advantages. The concentration of calcium in the solution was reduced by microorganism, facilitating the presence of additional calcium ions that acted as connecting nodes for various functional groups. In addition, the microorganisms promote the secretion of microvirin to enhance the aggregation of neighboring cells. And 16 s rRNA sequencing suggested Rhodobacter could be a potential contributor to Microcystis colony formation. These findings can promote the understanding of the relationship between cyanobacteria and other microorganism, and achieve deeper explanations of algal colony formation mechanism in aquatic environment, thus improving the theory of cyanobacterial bloom formation.