Blue-green bacteria - Chroococcus
The cells of Chroococcus usually are hemispherical and in pairs, with their straight sides facing one another. They are embedded in mucilage. Characteristic is the blue-green colour. The images series show the division process from two up to four-celled colony.
The diameter of the colony can be 40 my (1my=1/1000mm). The images show Chroococcus turgidis, which is one characteristic species in different marches. Nevertheless the species also can occur in open freshwater sea.