Effect of temperature on growth and macromolecular biosynthesis in Cryptococcus species

Cryptococcus neoformans, a pathogenic yeast, grows at temperatures between 25 and 37 degrees C. However, the closely related non-pathogen C. albidus exhibits restricted growth at temperatures above ambient with little or no growth at 37 degrees C. The inhibition of growth of the non-pathogen, as measured by turbidity, cell number, and per cent budding, is reversible after 48 hr at the non-permissive temperature (37 degrees C). Growth cessation at 37 degrees C is accompanied by a corresponding decrease in DNA synthesis, which is not observed in C. neoformans. RNA and protein synthesis in C. albidus and C. neoformans are only slightly affected at the elevated temperature. Degradation by nucleases does not seem to account for the differences found in this cumulative DNA synthesis in C. albidus at 25 and 37 degrees C. These facts suggest that C. albidus may possess a thermo-sensitive defect in the machinery responsible for the initiation of DNA replication.