Physiological and Morphological Studies of a Morphological Mutant in Neurospora crassa Stimulated by Sorbose

1. Physiological studies of a morphological mutant strain of Neurospora designated melon-1 (mel-1) have shown that the mutant strain responds differently to sorbose in the medium than does wild type. Although in a sucrose-containing medium sorbose inhibits the growth of wild type and increases the frequency of hyphal branching, it stimulates the growth of mel-1 and decreases the frequency of branching. 2. Xylose or lactose in combination with sucrose also produces an increased growth rate in mel-1 but not in wild type. Mel-1 utilizes lactose or xylose more effectively in comparison to its utilization of sucrose than does wild type. 3. Sorbose in combination with glucose, mannose, maltose, or possibly xylose, gives stimulation of growth in mel-1. In combination with fructose, galactose, or arabinose, sorbose has little, if any, effect on the growth rate of mel-1. Of the sugars tested in combination with sorbose, lactose and arabinose are the only ones which with sorbose, are inhibitory to mel-1. The sugars which with sorbose give the least effects on mel-1 are the ones which with sorbose inhibit wild type most strongly.