Effects of Nutrients, Temperature and Relative Humidity on Germination and Longevity of the Ascospores of Chaetomium Thermophile Var. Coprophile

SUMMARY

Ascospores of C. thermophile var. coprophile germinated in distilled water; addition of nutrients increased the percent germinating and also shortened the latent period. A vesicle emerged through the pore, quickly protruding one or two germ tubes if nutrients were present. The vesicle did not form in distilled water. Approximately 75% germinated after 6 hr at 50 C. Germination occurred between 30 and 59 C; the optimum was 50–55 C. Spore concentration had no significant effect upon germination. A short maturation period is required since ascospores from 4- and 6-day-old cultures germinated in a lower percentage than those from older cultures. However, they require no activation treatment. The ascospores are not thermoduric and failed to survive 1 hr exposure to 63 C. The thermal death point (all cells killed in 10 min) was between 65 and 67 C. Exposure to temperatures above the maximum invoked a delay in germination when the ascospores were reincubated at an optimum temperature. Ascospores in a dry state and stored at low relative humidities retained their viability longer and could survive longer exposures to high temperatures than when suspended in water or stored dry at high relative humidities.