Role of extracellular polymeric substances in resistance to allelochemical stress on Microcystis aeruginsosa and its mechanism

Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety. However, the suppression efficiency is affected inevitably by the extracellular polymeric substances (EPS) produced by cyanobacteria, and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce. For the study, two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa . Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae, especially in stabilizing the metabolism and photosynthetic activity of algal cells. The aggregation rate of algal cells increased with the increase of EPS secretion, which alleviated the stress of allelopathy. Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals, and the EPS-allelochemicals complex were formed by chemical bonding. This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.