Patterns of morphogenesis in the branching, filamentous cyanobacterium were examined by light and electron microscopy. Morphologically different types of filaments possessed, and were restricted to, distinct modes of cell division. Division in narrow and lateral branch filaments was always perpendicular to the long axis of the filament, indicating that these filaments were involved principally with trichome elongation. Division in wide filaments was either diagonal or (more often) parallel to the long axis of the filament, the latter enabling production of lateral branches. Cells of filaments in transition between the narrow and wide forms changed in shape and size, but divided only rarely. Wide cells that produced lateral branches were ultrastructurally identical to the other cells in wide filaments and were not surrounded by sheath material; branches did not arise by germination of akinetes. The morphological and ultrastructural characteristics of successive branch-filament cells (starting proximal to the parental filament) ranged from those typical of wide-filament cells to those typical of narrow-filament cells. Wide cells differed ultrastructurally from narrow cells in containing fewer ribosomes, less nuclear material, and more reserve materials. Wide cells lacked characteristic ultrastructural features of akinetes or other resting cells, appearing instead to be active vegetative forms. Lateral branches were released from parental filaments by deterioration of specific wide-filament cells.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error