SUMMARYA new isolate of Neurospora crassa displays a rhythm in its growth pattern. As the mycelium grows along the surface of the medium it begins, after the 12th hr, to form aerial hyphae at the growing front. This aerial growth continues until the 24th hr of growth and then stops. Surface growth continues until about the 32nd hr, when aerial hyphae are again formed. This alternation of surface and aerial hyphae results in a colony with zones or bands of mycelia of different densities. The rhythm is circadian, about 24 hr, and is perpetuated under conditions of constant light, temperature and humidity. The rhythm has remained steady in continuous darkness for over 2 months. Banding can be somewhat influenced by temperature and light but is not synchronized by these factors. A heat sensitive factor can be isolated from the growth medium which will eliminate the rhythm.
Cultures of Neurospora crassa that are shaken are capable of producing conidia on an [Formula: see text] medium which does not support conidial formation under standing conditions. A decrease in oxygen tension from 160 mm Hg causes a regular decrease in growth rate, a promotion in alcohol production, and a delay in conidia formation. In a medium with [Formula: see text] as the nitrogen source, oxygen tensions from 160 to 60 mm Hg do not greatly alter the growth rates, alcohol production is increased, and conidiation is delayed. Oxygen tensions below 60 mm Hg further delay conidiation, sharply decrease dry weight, and accelerate the production of alcohol 20 to 30% over amounts produced in the [Formula: see text] medium.
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