Phenotypic characterization of a Candida albicans strain deficient in its major exoglucanase

Both alleles of the XOG1 gene of Candida albicans, which encodes a protein with exoglucanase activity, were sequentially disrupted. Enzymic analysis of either cell extracts or culture supernatants of disrupted strains revealed that this gene is responsible for the major exoglucanase activity in C. albicans, although residual exoglucanase activity could still be detected. xog1 null mutants showed similar growth rates in both rich and minimal liquid medium as compared to the wild-type strain, indicating that the enzyme is not essential for C. albicans growth. In addition, no differences were observed between wild-type and xog1 null mutants with respect to their ability to undergo dimorphic transition. However, small but repeatable differences were found between the wild-type and the null mutant with respect to susceptibility to chitin and glucan synthesis inhibitors. Using a murine model of experimental infection, no significant differences in virulence were observed. The xog1 null strain is thus a suitable recipient for studying Candida gene expression using the exoglucanase as a reporter gene.