EFFECT OF PHOSPHATE CONCENTRATION ON THE FINE STRUCTURE OF THE CYANOBACTERIUM,MICROCYSTIS AERUGINOSAKÜTZ. EMEND. ELENKIN

Abstract

SUMMARY Microcystis aeruginosa toxic strain UV-006 stored a fixed amount of polyphosphate in spherical granules located in the centroplasm. Twenty four hours of phosphate starvation induced use of stored polyphosphate, manifested by reduction in granule numbers. Reintroduction of 2, 4 or 8 mg l−1 K2HPO4 resulted in redeposition of polyphosphate in a critical number of centroplasmic polyphosphate granules. Growth rate was unaffected by phosphate concentrations, although the final cell yield was slightly lower at 8 mg l −1 Continued starvation decreased photosynthetic rate and growth ceased. Cells appeared senescent. Cyanophycin and polyglucoside reserves apparently increased in these cells, whilst thylakoids were reduced in number and reorientated away from. the cell wall and polyhedral bodies were lost. After the initial decrease, centroplasmic polyphosphate bodies increased to about half of the maximum numbers stored in cells grown in the presence of phosphate, suggesting that translocation of phosphorus from other areas in the phosphate-starved cell occurred. Two further polyphosphate deposition areas were observed. DNA fibrils may have represented nucleation sites for developing polyphosphate granules. Intrathylakoidal deposits were rare.