Abstract
A method, based on germination with 50 mm CaCl(2) and 40 mm sodium dipicolinate (Na(2)DPA), was developed for the determination of total viable counts of bacterial spores requiring heat activation. Incorporation of these germinating agents into Tryptone Glucose Extract Agar permitted plate-count enumeration of essentially 100% of Bacillus subtilis strain 5230 spores without a heat treatment. Other spore suspensions were surveyed for their response to CaCl(2) and Na(2)DPA, and for the subsequent removal of the heat-activation requirement for enumeration of maximal populations.