Lysis of growing yeast-form cells of Candida albicans by echinocandin: a cytological study.

Yeast form cells of Candida albicans 6406 were treated with echinocandin, a new antifungal agent, which, in the absence of osmotic protection, provoked the lysis of exponentially growing cells. Lysis did not occur in stationary-phase cells and when protein synthesis was blocked. In intact cells, the synthesis of glucan, but not other important wall components, was partially inhibited. A cytological study of the effects of echinocandin at lytic doses (3.0 microgram ml-1) on osmotically protected yeast cells revealed a substantial thinning of the bud cell wall and derangement of its constitutive layers within 5-10 min, showing that the balance of wall growth was quickly and critically affected by the drug. Associated with this effect, a number of membranous bodies of myelin-like appearance were often seen in close proximity to the plasmamembrane of the emerging bud. Later during treatment (15 min onwards) membranous, convoluted bodies were detected in the nuclear and other intracytoplasmic membranes. Subsequent lytic events, unevenly distributed in cell population, eventually brought about complete lysis of the cell cytoplasmic structure. These results suggest that echinocandin may block a biosynthetic step during wall construction, or that it could alter wall metabolism as a result of a primary interaction with membranes.