Abstract
ABSTRACT
Diel cycles drive cyanobacterial physiology, yet the transcriptional and metabolic networks underlying diel adaptation in bloom‐forming
Microcystis
remain poorly understood. We integrated physiological measurements, transcriptomics and metabolomics to investigate diel dynamics of
Microcystis aeruginosa
under a 14‐h:10‐h light–dark cycle.
M. aeruginosa
exhibited clear diel rhythms in photosynthesis, cell division, and cell volume, with daytime as the active growth phase. Transcriptomically, daytime‐upregulated genes were enriched in anabolic pathways (e.g., photosynthesis, fatty acid, chlorophyll and arginine biosynthesis), whereas nighttime‐upregulated genes were associated with catabolic pathways (e.g., TCA cycle and purine/pyrimidine metabolism). Transporter genes remained active throughout the cycle. Metabolically, daytime featured higher levels of carbon fixation intermediates, nitrogen‐rich peptides and purine nucleosides, while nighttime showed enrichment of α‐linolenic acid and caffeoyl tyrosine. The metabolic network was organized into two opposing but internally correlated modules: a day‐enriched anabolic module and a night‐enriched catabolic module. Collectively,
M. aeruginosa
orchestrates a tightly coordinated diel trade‐off between daytime anabolism and nighttime catabolism to optimize light energy utilization and metabolic efficiency. These findings provide a multi‐omics mechanistic basis for understanding how
M. aeruginosa
exploits diel cycles for competitive success and offer time‐sensitive insights for monitoring and managing cyanobacterial blooms.