Studies on the Heat Resitstance of Bacterial Spores
Part 1. on the Method of Determining the Heat Resistance, and the Effects of Several Factors
1951 Volume 25 Issue 2 Pages 104-108
Details
1951 Volume 25 Issue 2 Pages 104-108
(1) The method we used to determine the heat resistance of spores of aerobic bacteria is a modification of the method of O. B. WILLIAMS (1929). The spores were harvested from nutrient agar slant, suspended in sterile M/15 phosphate buffer of pH 7.0, and filtered through a sterile filter paper to remove clumps of spores. The spore suspension was counted by means of haernacytometer (Thoma) and diluted so as to contain a definite number of spores. Then the suspension was pipetted into small glass tubes and heated in a boiling water bath.
(2) The “basic heat resistance” of spores of the aerobes (i.e. the survival time at 100C. with spore concentration of 50 millions per ml.) are as follows;
Bac. subtilis…………10 minutes, Bac. mesentericus………10 minutes,
Bac, megatherium…8 minutes, Bac. mycoides…………10 minutes
Bac. natto……………16 minutes,
(3) The unfiltered spore suspension containing spore clumps shows higher heat resistance than the filtered suspension. But in the former case the “skips” occurs and it is impossible to obtain definite results.
(4) The effects of several factors on heat resistance of spores of Bac. subtilis were pursued. (The results are shown in Tables 3, 4, 5 and 6)
