GERMINATION OF DESICCATED AGED AKINETES OF ALKALIPHILIC CYANOBACTERIA

Morphological and biochemical changes associated with synchronous germ ination of mature, aged and desiccated akinetes of two alkaliphilic cy anobacteria, Cyanospira rippkae and Cyanospira capsulata, are describe d. Akinetes of both strains proved to be highly resistant to desiccati on, being able to germinate, in the presence of either N-2 Or nitrate as nitrogen source, with a germination frequency of more than 90% afte r seven years of storage in a dried state. The first cell division occ urred after 8-10 h of incubation, thereafter the germlings of the two strains followed a different pattern of cell differentiation. Heterocy sts were first noted, in a terminal position, at 16-18 h in three-cell ed germlings of C. capsulata and at 21-24 h in C. rippkae, when germli ngs were at least seven cells in length. Akinetes of both species poss essed, on a per cell basis, almost identical amounts of all photosynth etic pigments but, under nitrogen fixing conditions, photosynthetic ac tivity (oxygen evolution) was detected only after new proteins had bee n synthesized, before a functional heterocyst was developed and while total nitrogen remained constant. With energy provided by aerobic resp iration, a wide range of intracellular amino acids characteristic of p roteins was utilised to sustain the new protein synthesis. The end of this biosynthetic activity coincided with the timing of the first cell division. From this stage on, no changes in protein concentration occ urred until mature heterocysts were developed. In the presence of nitr ate, no significant changes in the major germination events were obser ved.