REQUIREMENTS OF TWO TEMPERATURE‐SENSITIVE MUTANT STRAINS OF NEUROSPORA CRASSA FOR GROWTH AT ELEVATED TEMPERATURES

Abstract

Two mutant strains of Neurospora crassa failed to grow at 32 C in a minimal medium in which they grew well at 25 C. Both grew in the medium at 30 C after a relatively long lag phase, although the amount of growth at the maximum stationary phase was much less than in similar cultures incubated at 25 C. The addition to the minimal medium of relatively high concentrations of polyethylene glycol “400” or of any one of several sugars or inorganic salts increased growth of each strain at 30 C and enabled each to grow to a limited extent at 32 C. Concentrations of NaCl, polyethylene glycol “400” and glucose most favorable for growth at 30 and 32 C were inhibitory at 25 C. The osmotic pressures exerted by the media containing optimum concentrations of NaCl, of polyethylene glycol “400” or of lactose for the growth of each strain at 30 or at 33 C were within the same general range. Possible explanations of the effects of increased osmotic pressure of the medium upon growth of the strains at elevated temperatures are discussed.