Adams, J. N. (University of Georgia, Athens), Barbara G. Painter, and W. J. Payne. Effects of sodium caprylate on Candida albicans. I. Influence of concentration on ultrastructure. J. Bacteriol. 86:548-557. 1963.-Morphological effects of exposure to various concentrations of sodium caprylate were studied in living cells and ultrathin sections of Candida albicans. Budding was inhibited when cells were cultured in 0.0025 m sodium caprylate. Cells relieved from treatment at this concentration initiated reproductive processes at a much-stimulated rate. Momentary or 30-min exposures to 0.1 m caprylate affected cells in much the same manner as those treated at the lower concentration. Alteration of ultrastructure was brought about by treating with 0.0025 and 0.005 m concentrations prior to embedding and sectioning. Condensation of vacuolar material, change in size and number of mitochondria, loss of mitochondrial cristae, and increased electron density of the cytoplasm were observed. Cellular integrity was progressively lost as a result of treatment at levels up to 0.1 m. The highly electron-dense cytoplasm of cells cultured in media containing 0.025 m or higher inhibitor appeared to break into irregular masses, but the nucleus and vacuole sometimes could be identified. Cells treated at the 0.1 m level contained a condensed mass of opaque and unidentifiable cytoplasmic constituents within the skeletal cell wall. Cytological observations were correlated with physiological studies.