Expression of C. albicans genes during GI tract colonization and influence of efg1, efh1 and cph1 mutations. Candida albicans

The goals of this study were to identify the Efg1p-regulon during GI tract colonization and to compare C. albicans gene expression during colonization of different organs of the GI tract. Our results identified significant differences in gene expression between cells colonizing the cecum and ileum. In addition, during laboratory growth, efg1- null mutant cells grew to a higher density than WT cells. The efg1- null mutant grew in depleted medium, while WT cells could only grow if the depleted medium was supplemented with carnitine, a compound that promotes the metabolism of fatty acids. During colonization, efg1- null mutant cells expressed higher levels of genes involved in lipid catabolism, carnitine biosynthesis and carnitine utilization in comparison to colonizing WT cells. This altered gene expression supports the ability of efg1- cells to hypercolonize naïve mice. Overall design: C. albicans cells (WT, efg1-, efg1- efh1- or efg1- cph1-) were inoculated into antibiotic-treated BALB/c mice by oral gavage. Contents of the cecum and ileum were collected and frozen in RNALater. Reference cells (WT C. albicans) were grown in YPD medium at 37oC to exponential phase. Total RNA was extracted from both all samples. Sample of C. albicans isolated from GI tract organs was compared to reference on microarray. Between 4 and 7 microarray hybridizations, with dye swaps, were performed for each sample.

本研究旨在鉴定胃肠道（GI tract）定植过程中的Efg1p调节子（Efg1p regulon），并比较白色念珠菌（Candida albicans, C. albicans）在胃肠道不同器官定植时的基因表达谱。研究结果显示，定植于盲肠与回肠的细胞之间存在显著的基因表达差异。此外，在实验室培养条件下，efg1基因缺失突变体（efg1- null mutant）的细胞密度较野生型（wild type, WT）细胞更高；该突变体可在耗尽型培养基中生长，而野生型细胞仅能在耗尽型培养基添加肉碱（carnitine，一种促进脂肪酸代谢的化合物）时才可正常增殖。在定植过程中，与定植的野生型细胞相比，efg1缺失突变体细胞的脂质分解代谢、肉碱生物合成及肉碱利用相关基因的表达水平显著升高，这一基因表达改变支持了efg1-细胞可过度定植于未致敏小鼠的能力。总体实验设计：将白色念珠菌细胞（野生型、efg1-、efg1- efh1-或efg1- cph1-）通过灌胃法接种至经抗生素处理的BALB/c小鼠；收集盲肠与回肠内容物，置于RNALater试剂中冻存；参照组细胞为在37℃、YPD培养基中培养至指数生长期的野生型白色念珠菌；提取所有样本的总RNA，将从胃肠道器官分离的白色念珠菌样本与参照组样本进行微阵列（microarray）杂交；每个样本均完成4至7次微阵列杂交实验，并设置染料交换（dye swap）对照。