Evolutionary plasticity of cyanobacteria under persistent anoxia: mechanistic insights from marine blue holes and global ecological implications

Cyanobacteria are generally viewed as obligate oxic photoautotrophs. However, this paradigm was challenged by Z. Li, H. Zhang, T. Wei, L. He, and Y. Wang in Applied and Environmental Microbiology (92:e02576-25, 2026, https://doi.org/10.1128/aem.02576-25 ); this group identified transcriptionally active Synechococcus in the dark, permanently anoxic Yongle Blue Hole using integrated metagenomic and transcriptomic analyses. This finding suggests adaptive streamlining under long-term oxygen limitation, expands the recognized ecological range of phototrophic microorganisms, and highlights the potential relevance of microbial adaptation to future ocean deoxygenation.