Metabolic activities of isolated akinetes of the cyanobacterium Nostoc spongiaeforme.

Intact akinetes (spores) of the cyanobacterium Nostoc spongiaeforme can be isolated free of vegetative cells and heterocysts. The akinetes remain viable for at least 2 weeks in distilled water. They do not germinate in water but do so readily when transferred subsequently to cyanobacterial growth medium. Isolated, nongerminating akinetes incorporated 35S from Na235SO4 into protein and lipid. Similar incorporation was observed when akinetes were isolated from old cultures (containing primarily akinetes) which were labeled with Na235SO4 for 4 to 5 h before isolation. The metabolic activities of isolated akinetes were therefore not a factitious response to the isolation procedure. Autoradiographs of radioactive akinetes showed that 35S was incorporated by virtually all akinetes, rather than by a small subpopulation of active cells. Akinetes consumed O2 in the dark and, in a dichlorophenyl dimethylurea-sensitive reaction, evolved O2 in the light. We conclude that akinetes are metabolically active under conditions in which germination does not occur.