Morphogenesis and fine structure of Leucothrix mucor and effects of calcium deficiency.

Phenotypic expressions of morphogenesis and fine structure of Leucothrix mucor were determined when the organism was grown with and without added CaCl(2) in a synthetic seawater medium. Evidence is presented to show that a bulb can form in the absence of a knot formation and that a bulb may give rise to a "germ-tube." In comparison with normal cells, which show transverse septa at right angles to the axis in dividing cells, the bulbs exhibited transverse septa at odd angles, which may explain the mechanism of bulb formation. The most striking morphological feature due to Ca(++) deficiency was the absence of rosettes; instead, the culture showed an extremely filamentous morphology and a peculiar cord formation. Also, the Ca(++)-deficient cells contained heavily stained intracytoplasmic granules which possibly represent tight packing of the smaller particles of ribonucleoprotein. Various bulbous forms observed in the Ca(++)-deficient culture showed more pronounced elaboration of mesosomes as intracytoplasmic structures than those seen in the complete medium.