Growth and Division of Some Unicellular Blue-green Algae

SUMMARY: The growth of microcolonies of six strains of unicellular blue-green algae was studied by time-lapse photomicrography. The four rod-shaped strains divided regularly in a plane perpendicular to the long axis of the cell; one spherical strain divided successively in two planes, and one in three planes, perpendicular to one another. Anacystis nidulans and the other rod-shaped blue-green algae studied have a very restricted ability to form chains, four-celled elements being the longest ones observed in slide cultures. They are therefore unicellular organisms, in no way different with respect to development from rod-shaped unicellular bacteria. The recent proposal that A. nidulans is filamentous and should be reclassified in the genus Phormidium is based on a mis-understanding of the nature of unicellularity among procaryotic organisms.