Cyanobacteria Colonies Can Weather Any Storm express
In the freshwater lakes, cyanobacteria Microcystis often cause toxic blooms. They gather into colonies — elastic little spheres, like dense jelly. The cells are glued together by a special substance based on carbon, acting as a powerful natural adhesive. Scientists tested these "jelly balls" for the first time and found their strength astonishing. Regular waves in lakes are tens of times weaker than needed to break a colony. Even a fierce storm can't smash these living blobs: they withstand forces 100 times greater than typical water mixing.
Surprisingly, when phosphorus is scarce, the colonies don't weaken: they actually get tougher. The bacteria seem to remodel their slimy matrix into a "siege mode," making it stiffer. From a physics standpoint, such a structure has low entropy — little disorder, hence its stability. This discovery explains why toxic blooms are so hard to stop and hints at future strategies: perhaps the key is learning to dismantle these miniature fortresses.
Original abstract
as written by the authors arXiv:2604.27760
Toxic cyanobacterial blooms are a growing environmental concern that affects freshwater ecosystems, drinking water supplies, and public health. The cyanobacterium Microcystis is among the most important bloom forming species. It often grows in large colonies, which enhances its flotation, reduces grazing, and improves nutrient regulation. Microcystis cells are held together by a matrix of extracellular polymeric substances (EPS), making colony mechanics crucial for bloom formation. However, an analysis of the biomechanical properties of cyanobacterial colonies, and how these properties relate to environmental conditions like nutrient availability, remains largely missing. Here, we use micropipette force sensors to quantify the linear and non-linear mechanical properties of individual colonies at single-cell resolution. Bulk shear rheology complements these measurements by probing macroscopic properties. The measured tensile strength and yield stress are broadly comparable to those of bacterial biofilms and are far greater than the hydrodynamic stresses typically found in wind-mixed lakes. This implies that cyanobacterial colonies are highly resistant to fragmentation by natural mixing processes. We also show that low nutrient availability, particularly low phosphorus, produced stronger colonies, suggesting structural changes in the EPS. Overall, our results establish mechanical testing as a tool for a more complete and physically grounded understanding of cyanobacterial colony formation.
Microcystis colonies withstand forces 100 times stronger than those typically found in lakes during a storm.