Studies in the Physiology of Parasitism

Enzyme preparations were obtained from culture filtrates of the soft-rot pathogens Botrytis cinerea Pers. and Bacterium aroideae (Townsend) Stapp grown in simple synthetic nutrient media. Crude culture filtrates and preparations purified by acetone-precipitation and dialysis had three characteristic properties. They (i) decreased viscosity of pectin and pectate solutions, (ii) macerated parenchymatous tissues of higher plants, and (iii) killed cells of tissues so macerated. A parallelism was demonstrated between activity estimated by these three criteria. 2. B. cinerea enzyme preparations were active from about pH 3.5 to pH 6.0, activity decreasing rapidly from pH 6.o to nearly nil at pH 8.0. Conversely B. aroideae was most active above pH 8.0, activity decreasing progressively to nearly nil at pH 5.5. 3. Both enzymes lost much activity on prolonged dialysis against distilled water and this was not recovered on readdition of dialysed salts. On dialysis against certain salts or salt mixtures reduced or negligible losses occurred. 4. Plasmolysing concentrations of salts or non-electrolytes greatly retarded the killing action of the enzyme preparations, the effect being out of all proportion to that on maceration or on rate of pectin degradation. 5. Protoplasts were isolated in the plasmolysed condition from certain tissues. These were resistant to toxicity in similar manner to those inside the tissue.