Basrai M A, Naider F, Becker J M
Department of Microbiology, University of Tennessee, Knoxville 37996.
J Gen Microbiol. 1990 Jun;136(6):1059-65. doi: 10.1099/00221287-136-6-1059.
Lucifer yellow (LY), an impermeable fluorescent dye used as a marker for fluid phase endocytosis, was internalized by Candida albicans. As observed by fluorescence microscopy, incubation of C. albicans with LY in potassium phosphate buffer (pH 6.0) and glucose (2%, w/v) resulted in localization of the dye inside vacuoles. Sodium azide and carbonyl cyanide m-chlorophenylhydrazone, which are inhibitors of energy metabolism, decreased the uptake of the dye. The optimum temperature for uptake was 30 degrees C; no internalization was observed at 0 degrees C. Quantification of cell-associated LY by fluorescence spectrometry showed an uptake linear with time and not saturable over a 400-fold range of concentration. Thus, C. albicans internalized LY into vacuoles by a nonsaturable and time-, temperature- and energy-dependent process consistent with fluid phase endocytosis. Both the yeast and mould phase of this dimorphic fungus endocytosed LY. Growth in complex medium appeared to be required to enable the cells to internalize LY. However, addition of peptone or yeast extract to the phosphate buffer/glucose assay medium interfered with LY uptake by causing an apparent increase of exocytosis. These studies provide the first evidence of fluid phase endocytosis in C. albicans and may explain how some large molecules, such as toxins and cationic proteins, enter C. albicans.
荧光黄（LY）是一种不可渗透的荧光染料，用作液相胞吞作用的标记物，白色念珠菌可将其内化。通过荧光显微镜观察，在磷酸钾缓冲液（pH 6.0）和葡萄糖（2%，w/v）中，白色念珠菌与荧光黄一起孵育，结果显示染料定位于液泡内。叠氮化钠和羰基氰化物间氯苯腙是能量代谢抑制剂，它们会降低染料的摄取。摄取的最适温度为30℃；在0℃时未观察到内化现象。通过荧光光谱法对细胞相关荧光黄进行定量分析，结果显示摄取量与时间呈线性关系，并且在400倍的浓度范围内不饱和。因此，白色念珠菌通过与液相胞吞作用一致的非饱和、依赖时间、温度和能量的过程将荧光黄内化到液泡中。这种二态真菌的酵母相和霉菌相均能胞吞荧光黄。似乎需要在复杂培养基中生长才能使细胞内化荧光黄。然而，在磷酸盐缓冲液/葡萄糖测定培养基中添加蛋白胨或酵母提取物会干扰荧光黄的摄取，因为会导致明显的胞吐作用增加。这些研究首次提供了白色念珠菌液相胞吞作用的证据，并可能解释了一些大分子，如毒素和阳离子蛋白，是如何进入白色念珠菌的。
