EFFECT OF SULFUR STARVATION ON THE MORPHOLOGY AND ULTRASTRUCTURE OF THE CYANOBACTERIUM GLOEOTHECE SP PCC-6909

Gloeothece sp. PCC 6909 is a unicellular, nitrogen-fixing cyanobacteri um that accumulates sulfate in its sheath. An ultrastructural study of sulfate-deficient and normal Gloeothece sp. PCC 6909 cells was carrie d out. The physiological alterations, caused by sulfur starvation, wer e related to important morphological alterations in the cell: a struct ureless sheath, accumulation of cyanophycin, polyhydroxybutyrate and g lycogen granules, and disintegration of thylakoidal membranes. Most of these changes were reversed by the addition of sulfate to the culture medium. The important role of sulfate in the sheath structure was dem onstrated.