EFFECT OF OSMOTIC-STRESS ON YIELD AND POLYOL CONTENT OF DICARBOXIMIDE-SENSITIVE AND DICARBOXIMIDE-RESISTANT STRAINS OF NEUROSPORA-CRASSA

A wild type strain and an os-1 mutant of Neurospora crassa were subjected to osmotic stress in media of high osmolality (865 mosmol kg-1) adjusted with sodium chloride, potassium chloride, glucose, fructose, mannitol or glycerol. The strains produced similar amounts of mycelia when grown in basal medium (125 mosmol kg-1) or in medium of high osmolality adjusted with glycerol. In media adjusted with other osmotica, yields of wild type and mutant mycelia were reduced by approximately 35% and 90%, respectively. Both strains accumulated large amounts of glycerol and, to a lesser extent, mannitol when grown in media of high osmolality adjusted with sodium chloride. These alditols contributed a solute potential equivalent to approximately 30-40% of the external water potential. Wild type and mutant mycelia that had been washed during harvesting with water or iso-osmotic culture medium contained much less glycerol and mannitol than equivalent unwashed mycelia. The osmotic sensitivity of the os-1 mutant is discussed in relation to osmotic adjustment and retention of glycerol.