Comparative studies of the effect of physical factors on endospores and conidiospores of some thermopiles and mesophiles: effect of irradiation, freezing and thawing

The sensitivty of endospores and conidiospores of some thermophilic and mesophilic organisms to gamma-radiation and freezing and thawing was compared. Endospores were more resistant to gamma-radiation than conidiospores. Within each group, spores of Thermophiles were more radioresistant than spores of mesophiles. The reverse was mostly true for the effect of freezing and thawing, where endospores of Bacillus stearothermophilus were the most sensitive to freezing and thawing. The DR value for endospores of Thermoactinomyces vulgaris, B. stearothermophilus and B. subtilis are in respect 2.70, 2.25, and 3.0 KGY, while the DR value for conidiospores of Aspergillus fumigates, Penicillum sp., Streptomyces anadii and Streptomyces sp., are in respect, 0.6, 0.41, 0.708 and 2.25 KGY. Slow freezing and slow thawing is generally more damaging than fast freezing and fast thawing

Comparative studies of the effect of heat on endospores and conidiospores of some thermopiles and mesophiles

Thermal resistance of endospores of thermophilic and mesophilic organisms was compared to that of conidiospores. The thermal resistance of the examined spores canoe arranged acccrding to the following order: endospores of thermophilic Bacillus sp. > endospores of Thermoactinomyces sp. > endospores of mesophilic Bacillus sp. > coniiospores of thermotolerant streptomyces sp. > Conidiospores of thermophilic fungi > conidiospores of mesophilic fungi

effect of the water activity of the growth medium on pesticide sensitivity in saccharomyces cerevisiae and S rouxii

Yeast cells of Saccharomyces cerevisiae and the osmotolerant yeast S. rouxii were grown aerobically and anaerobically on media the water activity of which was regulated either by sodium chloride or glycerol. The yeast cells were washed and suspened either in isotonic solutions of either solutes or in distilled water. Cells were then exposed to three pesticides namely the fungicide Antracol, the insecticide Supracide, and the akaricide Akar. Results were expressed as D-values [Decimal death time i.e, time in minutes required to kill 90% of cells]. Results showed that Supracide exerted the higest toxicity on both yeasts, followed by Akar, while Antraclo was the least toxic. Also, cells of S. cerevisiae showed higher response to the water activity of the growth medium in relation to pesticide sensitivity over S. rouxii in presence of either sodium chloride or glycerol