Normal adaptation of Candida albicans to the murine gastrointestinal tract requires Efg1p-dependent regulation of metabolic and host defense genes

Although gastrointestinal colonization by the opportunistic fungal pathogen Candida albicans is generally benign, severe systemic infections are thought to arise due to escape of commensal C. albicans from the gastrointestinal (GI) tract. The C. albicans transcription factor Efg1p is a major regulator of GI colonization, hyphal morphogenesis, and virulence. 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. During colonization, efg1- null mutant cells expressed higher levels of genes involved in lipid catabolism, carnitine biosynthesis, and carnitine utilization than did colonizing wild-type (WT) cells. 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 grow only if the depleted medium was supplemented with carnitine, a compound that promotes the metabolism of fatty acids. Altered gene expression and altered growth capability support the ability of efg1- cells to hypercolonize na\uefve mice. Also, Efg1p was shown to be important for transcriptional responses to the stresses present in the cecum environment. For example, during colonization, SOD5, encoding a superoxide dismutase, was highly upregulated in an Efg1p-dependent manner. Ectopic expression of SOD5 in an efg1- null mutant increased the fitness of the efg1- null mutant cells during colonization. These data show that EFG1 is an important regulator of GI colonization. \ua9 American Society for Microbiology. All Rights Reserved.Peer reviewed: YesNRC publication: Ye

The DnaK homologue of the marine Vibrio sp. strain S14 binds to the unprocessed form of a carbon starvation-specific periplasmic protein

The Escherichia coli DnaK homoiogue in Vibrio sp. strain S14 was shown to possess chaperone function for translocation during carbon starvation. This was demonstrated by using the method of co‐immunoprecipitation. DnaK co‐precipitated with the carbon starvation‐specific periplasmic space protein Csp5 three hours after the onset of carbon starvation. Pulse‐chasing of the protein with radiolabelled methlonine followed by the addition of an excess of unlabelled methionine demonstrated that the Csp5 protein was translocated across the inner membrane. Only the cytoplasmic unprocessed precursor form of Csp5 co‐precipitated with DnaK. The non‐covalent binding between the two proteins was found to be ATP‐dependent, as the addition of ATP released the interaction between DnaK and the precursor form of Csp5, as was shown both on silver‐stained SDS‐poly‐acrylamide gels and by Western blot analysis. We suggest that DnaK maintains the carbon starvatlon‐Inducible protein Csp5 in a translocation‐competent form In the cytoplasm. Copyright © 1994, Wiley Blackwell. All rights reserve