The effect of 5-fluorocytosine on the blastospores and hyphae of Candida albicans.

In Candida albicans the continued increase in dry weight, in cell volume and in hyphal length during 5FC treatment is mainly due to increased amount of carbohydrate despite the decreased amounts of nucleic acids. Incorporation studies with 32PO4 (for RNA) in C. albicans and with 3H-thymidine-monophosphate (for DNA) in a thymidine-utilising strain of Saccharomyces cerevisiae have shown that the decreased amounts of nucleic acids were due to an inhibition of synthesis of RNA and DNA by 5FC. Nuclear-staining techniques on the hyphal phase of C. albicans showed that 5FC inhibits nuclear division. The changes in amounts of protein during 5FC treatment do not wholly explain the changes in cell size although 14C-histidine incorporation experiments showed that protein synthesis continued in the presence of 5FC. 14C-glucose incorporation in the presence of 5FC showed an initial accelerated synthesis of carbohydrate with a maintained level of synthesis after 16 h. This abnormal pattern of synthesis correlates with the increase in amount of carbohydrate and in cell size and hyphal elongation. 5FC inhibits DNA synthesis, and all manifestations of unbalanced growth that culminate in the cell volume changes appear to be a consequence of that inhibition.