White rot fungi as a multifaceted biocontrol agent: Metabolic disruption and algal inhibition in Microcystis aeruginosa.

Microcystis aeruginosa is a prevalent cyanobacterium linked to water eutrophication and harmful algal blooms. While bacterial control strategies are well-studied, the effects of white rot fungi on Microcystis aeruginosa are less understood. This study examines the impact of whole fungal liquid, its centrifuged supernatant, and sterilized solutions on the algae's physiological and biochemical traits. Metabolomics and multivariate analysis identified significant changes in 47 metabolic markers, including carbohydrates, amino acids, and fatty acids, across treatments. The complete fungal liquid exhibited the strongest algicidal effect, likely due to synergistic solubilization mechanisms mediated by extracellular enzymes such as manganese peroxidase, catalase, and laccase. Notably, algicidal activity persisted even after sterilization, suggesting the presence of non-proteinaceous compounds like polysaccharides or lipids. The metabolic disturbances included downregulation of the TCA cycle and reduced fatty acid synthesis, leading to inhibited photosynthesis and compromised nucleic acid integrity in the algal cells. This research enhances our understanding of how white rot fungi disrupt Microcystis aeruginosa metabolism, providing a theoretical basis for their potential use in bioremediation of eutrophic aquatic environments.