| Abstract: | Cultures were cloned from a sample containing Microcystis aeruginosa, M. flos-aquae and a few morphological intermediates. The M. aeruginosa cultures remained distinct from the M. flos-aquae cultures in (a) cell size, (b) cell aggregation pattern, (c) width of the mucilage surrounding the multicellular colonies, (d) sharpness of the mucilage boundary, (e) efect of 0.1–1.0 μM calcium chloride on the disaggregation of multicellular colonies, (f) frequency of mucilage mutants and (g) colony morphology on agar media. No M. flos-aquae culture produced morphs resembling M. aeruginosa, inconsistent with proposals that M. flos-aquae is a developmental stage or environmentally-induced variant of M. aeruginosa. After longterm cultivation, but not soon after origanal isolation, several M. aeruginosa cultures contained mutants with diminished mucilage production and an altered colony shape. |
