Comparative metabolomics of exudates between toxigenic and non-toxigenic Microcystis aeruginosa

Cyanobacterial Harmful Algal Blooms (CHABs, dominated by Microcystis aeruginosa) have received high attention for decades owing to the noxious and harmful secondary metabolites and toxins that they produce and release upon into water. Research on the active components and future risk assessment of them are demanded. M. aeruginosa strains could be characterized as ‘toxigenic’ (genomics containing mcy gene) or ‘non-toxigenic’ (genomics not containing mcy gene), according to whether they produce microcystins or not. We employed nontargeted metabolomics technique to compare components and their abundances in exudates from toxigenic M. aeruginosa strain (FACHB-905) and non-toxigenic strain (FACHB-526) at exponential and stationary growth stages. In total, 409 metabolites were identified and lipids, organoheterocyclic compounds and benzenoids were found with high abundances. The two strains in the same growth stage had similar metabolites, but more metabolites were accumulated at stationary phase than exponential stage. Although FACHB-905 exudated more metabolites than FACHB-526, some known bioactive and toxic metabolites, e.g. 7-ketocholesterol, glyceraldehyde and myristoleic acid, were significantly accumulated higher in FACHB-526 exudates. Our results would be valuable for further risk prediction of cyanobacterial booms, especially for the non-toxigenic strains, and healthy water management.