Cyanobacteria can switch between two forms of a protein called D1 in response to too much sunlight, helping them recover from damage to their photosynthesis. When exposed to high light levels, the main form of D1 is quickly replaced by an alternative form, which is then reversed when light levels return to normal. If this switch doesn't happen, the bacteria lose photosynthetic activity and struggle to recover. This ability to interchange D1 forms may be a unique defense mechanism that helps cyanobacteria deal with and bounce back from light-induced stress.