THE SECRETED ASPARTATE PROTEINASE OF CANDIDA-ALBICANS - PHYSIOLOGY OF SECRETION AND VIRULENCE OF A PROTEINASE-DEFICIENT MUTANT

It was established that Candida albicans grew rapidly in a simple medium containing yeast extract (0.2%, w/v) plus glucose (2%, w/v). These cultures were in or near to a state of nitrogen limitation and the concentration of secreted aspartate proteinase increased rapidly (within 3-4 h) on addition of BSA. Synthesis and secretion were apparently controlled both positively (induction by albumin or, more porobably, the peptides produced from it) and negatively (repression by NH4Cl). A small intracellular pool of the enzyme was detected during production of the enzyme and this pool decreased with the cessation of synthesis and secretion. A stable mutant, IR24, was isolated which secreted less than 0.3% of the amount of the proteinase exported by he parent strain ATCC 10261. The LD50 values for mutant IR24 and the parent strain administered intravenously to mice were > 1.0 x 109 and 1.6 x 106 c.f.u kg-1 respectively.