Summary: On the basis of a comparative study of 178 strains of cyanobacteria, representative of this group of prokaryotes, revised definitions of many genera are proposed. Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification. The differential characters proposed are both constant and readily determinable in cultured material. The 22 genera recognized are placed in five sections, each distinguished by a particular pattern of structure and development. Generic descriptions are accompanied by strain histories, brief accounts of strain properties, and illustrations; one or more reference strains are proposed for each genus. The collection on which this analysis was based has been deposited in the American Type Culture Collection, where strains will be listed under the generic designations proposed here.

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Generic assignments, strain histories, and properties of pure cultures of cyanobacteria

IN marked contrast to their freshwater counterparts, marine planktonic cyanobacteria are restricted to a few nostocalean genera, of which only Trichodesmium is capable of forming extensive water blooms1–3. We report here the widespread occurrence of a small, marine, chroococcalean cyanobacterium belonging to the genus Synechococcus.

Widespread occurrence of a unicellular, marine, planktonic, cyanobacterium

The efficiency of pigment extraction forms the crux of the spectrophotometric analysis of chlorophyll a. The alcoholic solvents, methanol and ethanol, proved to be superior to acetone and acetone with DMSO. Homogenisation and sonication did not improve the extraction in the alcoholic solvents. Boiling at 100°C had an adverse effect whereas complete extraction of the pigments was obtained at the solvents boiling point and allowing the samples to stand for 24 h in the dark.

R Kunisawa

Papers

Purification and properties of unicellular blue-green algae (order Chroococcales).