Diel asynchrony in the expanded characteristics of toxic cyanobacterial blooms revealed by integrated metabolomics and metagenomics.

We establish a field metabolomics protocol in Lake Taihu (China) and determined two critical parameters: the minimum amount of biomass for metabolomics and the daytime when metabolomes are stable. The minimum biomass is 475-950 µg dry weight (DW) or 204-408 ng DNA for F (phytoplankton) samples, and 940-1760 µg DW or 193-514 ng DNA for W (whole-water) samples. In a diel cycle, temporal taxonomical composition, metabolic state, and response to physiochemical factors progressed asynchronously between the F and W microbiomes. F peak growth (metabolic steady state) occurred 12-17 pm while W around 12 pm in metabolite identity, concentration, and molecular weight. 482 (∼50 %) metabolites highly correlated between the F and W microbiomes. Integrated analysis revealed different systematic changes between F and W sample, in taxon-associated metabolites, reactions, and biological functions: e.g., carbon metabolism and bioenergetics in F and amino acid metabolism and central metabolism in W samples. Metagenomics discovered important interspecific and intraspecific diversity using single-nucleotide polymorphism, and interactions between cyanobacteria and epibiotic bacteria. Diel intraspecific diversity shift inferred Microcystis aeruginosa and Anabaena sp. have different temperature optima experimentally verified. This integrated multi-omics protocol expands water microbiome analyses from conventional structure and function to diversity dynamics and interspecific metabolism and ecophysiology.

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