THE ENUMERATION OF THERMOPHILIC BACTERIA BY THE PLATE COUNT METHOD

Abstract

The estimation of the numbers of aerobic thermophilic bacteria by the plate count method was found to be greatly influenced by the composition of the diluent and by its temperature. A satisfactory diluent consisted of 0.8% KCl in M/200 pH 7.2 potassium phosphate buffer. The need of maintaining the temperature at 37 °C. and using the special diluent was demonstrated with pure cultures and with mixed cultures obtained by the enrichment procedure. In some cases, the new condition of plating gave counts 100 times those obtained by conventional means. Cultures which were almost completely free of spores were used in determining the optimum plating conditions.