Cyanobacteria have survived in other ways. One of the most interesting is throughsymbiosis, where a cell merges with another cell in a way that helps both survive. Themost dramatic example is that the chloroplast with which plants make food for themselvesis actually a cyanobacterium living within the plant's cell. The photosynthesis iscentered in the chloroplast, while the other parts of the cell provide a protectiveenvironment for the chloroplast and integrate it into the plant.
Given at least nine meters (roughly 30 feet) of water on the planet, photosynthetic microbes (including mats of algae, cyanobacteria, and other photosynthetic bacteria) and plant-like protoctists (such as floating seaweed or kelp forests attached to the seafloor) could be protected from "planet-scalding" ultraviolet flares produced by young red dwarf stars, according to of Caltech, principal investigator at the NASA 's .
As proposed by Andrew Goldsworthy in 1987, cyanobacteria and later chloroplast-related protists and plants developed after microbes that used a purple pigment bacteriorhodopsin that absorbs green light dominated the oceans, and so the new photosynthetic cyanobacteria were forced to use the left-over light with chlorophyll that reflects green light, which was too complex to change even after purple-reflecting photosynthetic lifeforms were no longer dominant (Debora MacKenzie, New Scientist, September 10, 2010).