Abstract
Abstract The effects of nitrogen and sulfur limitation on various cellular parameters of the cyanobacterium Synechococcus 6301 were studied by electron microscopy, morphometry and biochemical methods. Nitrate and sulfate starvation for 70 h results in a massive glycogen accumulation in parallel to a loss of soluble protein and chlorophyll. Phycobilisomes disappear prior to the degradation of photosynthetic membranes. For sulfate-starved cells, a formation of “storage granules” (poly-β-hydroxy-butyric acid) is typical which amount up to 10% of the cell volume. The composition of polar lipids is simple: equal parts of C 16:0 and C 16:1 are present under all nutritional conditions; their amount is directly correlated with the total cellular membrane area as determined by morphometry. Nitrate starved cells regenerate almost completely in structure and composition within 9 h after nitrate supplementation. Regeneration of sulfate starved cells is retarded; in spite of significant synthesis of phycocyanin within 9 h the cells still exhibit marked signs of starvation.
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