Cyanobacteria Surprise Scientists With Unexpected Evolutionary Shift

Researchers at the Institute of Science and Technology Austria (ISTA) have identified a surprising evolutionary shift in the cyanobacterium Anabaena sp. PCC 7120, where an ancient DNA segregation system has been repurposed into a new cytoskeleton that controls cell shape in multicellular cyanobacteria.

The discovery centers on a protein called CorM, which was previously thought to function solely in separating DNA during cell division. Through collaborative work involving the Loose group at ISTA, the Schur group at ISTA, the Institut Pasteur de Montevideo in Uruguay, Kiel University in Germany, and the University of Zürich in Switzerland, scientists found that CorM forms dynamic filaments both inside living cells and when rebuilt outside of them.

Using cryo-electron microscopy (cryo-EM), researchers visualized purified CorM filaments, revealing their structural properties. In living Anabaena cells, fluorescent labeling showed CorM filaments organized in patterns that influence cellular morphology, indicating a role beyond DNA segregation in maintaining cell shape and integrity.

Cyanobacteria are essentially pioneers of oxygenic photosynthesis,” says Benjamin Springstein, a postdoc in the Loose group at ISTA. “They are responsible for the Great Oxygenation Event about 2.5 billion years ago, when oxygen accumulated in the atmosphere and made aerobic life possible. Without them, it’s safe to say that none of us would be here today.”

Benjamin Springstein, ISTA

Springstein noted that while cyanobacteria like Anabaena have long been studied for their ecological and evolutionary significance—particularly their contributions to global biomass production and roles in carbon and nitrogen cycles—this finding reveals a previously unknown adaptation in their cellular architecture.

The research highlights that Anabaena, a model organism studied for over 30 years due to its multicellular structure, has evolved a novel cytoskeletal system from an ancestral DNA segregation mechanism. This represents a significant example of molecular exaptation, where existing proteins acquire new functions over evolutionary time.

Filament formation by CorM was observed to be dynamic, suggesting the cytoskeleton can rapidly respond to internal or external cues. Such adaptability may support the organism’s ability to thrive in extreme environments, ranging from hot springs to Arctic conditions, as well as urban surfaces like building roofs and walls.

Although the study focuses on Anabaena sp. PCC 7120, the researchers suggest that similar evolutionary shifts may exist in other multicellular cyanobacteria, implying broader implications for understanding cytoskeletal innovation across photosynthetic prokaryotes.

The work was conducted as part of ongoing efforts to understand bacterial cell biology at a mechanistic level, combining genetics, imaging, and biochemical approaches. No commercial applications or technological developments were described in the reported findings.