Chemical Activation of Ascospore Germination in Neurospora crassa.

In the red bread mold Neurospora crassa as in other pyrenomycetes the sexual spores, the ascospores, germinate only after the application of heat (Shear and Dodge, 1927; Goddard, 1935, 1938, 1939). When treated at a temperature of from 50 to 60 C for periods varying from 10 to 60 minutes the spores will germinate up to 100 per cent. Germination may occur without this treatment, the percentage depending on the condition of the spores and on the medium used. The spontaneous germination rate is usually higher on media fortified with malt and yeast extracts, hay infusion, etc., and may occasionally go as high as for treated spores. Recently, while a synthetic minimal medium was being used in which d-xylose was the carbon source, a consistently high percentage of spontaneous germination was observed. A number of experiments were then conducted in an attempt to determine the active agent involved. From these it appeared that xylose was much more effective after being autoclaved than after being filter sterilized. On the assumption that in the mineral solution (Fries no. 3, having a pH of 5.5) used in the medium and under the pressure and temperature of autoclaving there might be a slight conversion of the pentose into furfural (C4H80CHO), the latter was tried alone and proved very effective.