Jabra-Rizk M A, Falkler W A, Merz W G, Kelley J I, Baqui A A, Meiller T F
Department of Oral Medicine and Department of Oral and Cranofacial Biological Sciences Dental School, University of Maryland, Baltimore, USA.
Rev Iberoam Micol. 1999 Dec;16(4):187-93.
Adherence of yeasts to other microorganisms and epithelial cell surfaces is important in their colonization. Comparative studies based on the coaggregation of Candida dubliniensis versus Candida albicans with Fusobacterium nucleatum and other oral bacteria suggested differences in the surfaces of these yeasts. Transmission electron microscopy was used to test the hypothesis that there are morphologic variations in the cell surface of these two species. C. dubliniensis type strain CD36 and C. albicans ATCC 18804 were grown on Sabouraud's dextrose agar at various growth temperatures. In some experiments suspensions of yeast cells were treated with dithiothreitol. Fixation for transmission electron microscopy was accomplished using dimethylsulfoxide and alcian blue added to 3% paraformaldehyde and 1% glutaraldahyde in cacodylate buffer. The cell wall of both species was predominantly electron lucent and was visibly differentiated into several layers. A thin electron dense outer layer was seen with clearly visible fibrillar structures, closely associated to the cytoplasmic membrane. The length of the fibrils of the C. albicans cells grown at 37 degrees C was approximately two times greater than those of the cells grown at 25 degrees C. The fibrils of the 37 degrees C-grown cells were thin, distinct and tightly packed whereas those of the 25 degrees C-grown cells appeared blunt, loosely spaced and aggregated. C. dubliniensis demonstrated short, blunt fibrils appearing similar to those of the 25 degrees C-grown C. albicans cells. C. dubliniensis showed no difference in the density, length and arrangement of fibrils between the 25 degrees C and 37 degrees C growth temperatures. The shortest and most aggregated fibrils seen were of the 45 degrees C-grown C. albicans cells. Dithiothreitoltreated 37 degrees C-grown C. albicans cells revealed a distorted and partially destroyed fibrillar layer. In this investigation C. dubliniensis, unlike C. albicans, displayed an outer fibrillar layer that did not vary with variations in growth temperature. In addition, the fibrils on the C. dubliniensis cells were similar to those of the 25 degrees C-grown C. albicans in that they were considerably shorter and less dense than those of the 37 degrees C-grown C. albicans cells. It can be postulated, that C. dubliniensis exhibits constant cell surface characteristics consistent with hydrophobicity and that this property may give this species an ecological advantage. Therefore, C. dubliniensis may compete well in oral environments via enhanced attachment to oral microbes and other surfaces, perhaps even more efficiently than C. albicans.
酵母菌对其他微生物和上皮细胞表面的黏附在其定植过程中很重要。基于都柏林念珠菌与白色念珠菌与具核梭杆菌及其他口腔细菌的共聚集现象进行的比较研究表明，这些酵母菌的表面存在差异。采用透射电子显微镜来验证这两种酵母菌细胞表面存在形态学差异这一假说。都柏林念珠菌标准菌株CD36和白色念珠菌ATCC 18804在不同生长温度下于沙氏葡萄糖琼脂上培养。在一些实验中，酵母细胞悬液用二硫苏糖醇处理。透射电子显微镜观察的固定处理是通过向在二甲胂酸盐缓冲液中的3%多聚甲醛和1%戊二醛中添加二甲基亚砜和阿尔辛蓝来完成的。两种酵母菌的细胞壁主要呈电子透亮状，且明显可分为几层。可见一层薄的电子致密外层，伴有清晰可见的纤维状结构，与细胞质膜紧密相连。在3�C培养的白色念珠菌细胞的纤维长度约为在25�C培养的细胞的两倍。在37℃培养的细胞的纤维细、清晰且紧密排列，而在25℃培养的细胞的纤维显得钝圆、间隔松散且聚集在一起。都柏林念珠菌显示出短而钝的纤维，与在25℃培养的白色念珠菌细胞的纤维相似。都柏林念珠菌在25℃和37℃生长温度下，其纤维在密度、长度和排列上均无差异。观察到的最短且最聚集的纤维是在45℃培养的白色念珠菌细胞的。用二硫苏糖醇处理的在37℃培养的白色念珠菌细胞显示出纤维层扭曲且部分被破坏。在本研究中，与白色念珠菌不同，都柏林念珠菌显示出一层外部纤维层，其不会随生长温度变化而改变。此外，都柏林念珠菌细胞上的纤维与在25℃培养的白色念珠菌细胞的纤维相似，因为它们比在37℃培养的白色念珠菌细胞的纤维短得多且密度小。可以推测，都柏林念珠菌表现出与疏水性一致的恒定细胞表面特征，且这一特性可能赋予该菌种一种生态优势。因此，都柏林念珠菌可能通过增强对口腔微生物和其他表面的附着而在口腔环境中具有良好的竞争力，甚至可能比白色念珠菌更高效。
