Nutritional and enzymatic factors affecting conidiation in neurospora crassa

Includes bibliographical references (pages 37-41)Cultures of neurospora Crassa, strain SY4F8a, produce conidia on both the nitrate (c) and anm1onium (m) media designed by Turian(34). The number of conidia produced is consistently higher in nitrate grown cultures. The largest quantitative difference in conidiation(C 18 times greater than M)occurs in cultures grown at 20C for five days. The specific activity of isocitratase is three times greater in the C than in the M cultures, while the specific activity of nicotinamide adenine dinucleotidase(NADase)is 150 times greater in C cultures. Addition if ammonium chloride (0.005 M to 0.12M) to the nitrate medium causes a repression of condition, NADasa activity, and isocitratage activity. Conidiation and NADasa activity are repressed at all levels of ammonium tested, whereas repression of isocitatase activity occurs only at the highest concentration of ammonium tested. NADase activity and conidiation can be restored to half their maximum level by increasing the concentration of nitrate in the growth medium. Density gradient centrifugation in homogenates of nitrate grown cultures indicates that the NADase of N. crassa is localized in the soluble protein phase of the cell