D-ARABITOL METABOLISM IN CANDIDA-ALBICANS - CONSTRUCTION AND ANALYSISOF MUTANTS LACKING D-ARABITOL DEHYDROGENASE

Candida albicans produces large amounts of the acyclic pentitol D-arab itol in culture and in infected animals and humans, and most strains a lso grow on minimal D-arabitol medium, An earlier study showed that th e major metabolic precursor of D-arabitol in C. albicans was D-ribulos e-5-PO4, from the pentose pathway, that C. albicans contained ah NAD-d ependent D-arabitol dehydrogenase (ArDH); and that the ArDH structural gene (ARD) encoded a 31-kDa short-chain dehydrogenase that catalyzed the reaction D-arabitol + NAD <=> D-ribulose + NADH. In the present st udy, we disrupted both ARD chromosomal alleles in C. albicans and anal yzed the resulting mutants. The ard null mutation was verified by Sout hern hybridization, and the null mutant's inability to produce ArDH wa s verified by Western immunoblotting. The ard null mutant grew well on minimal glucose medium, brit it was unable to grow on minimal D-arabi tol or D-arabinose medium. Thus, ArDH catalyzes the first step in D-ar abitol utilization and a necessary intermediate step in D-arabinose ut ilization. Unexpectedly, the ard null mutant synthesized D-arabitol fr om glucose. Moreover, C-13 nuclear magnetic resonance studies showed t hat the ard null mutant and its wild-type parent synthesized D-arabito l via the same pathway. These results imply that C. albicans synthesiz es and utilizes D-arabitol via separate metabolic pathways, which was not previously suspected for fungi.