Effects of temperature and heat activation on germination of individual spores of Bacillus subtilis.

Phase intensity changes of individual germinating spores of Bacillus subtilis were determined by phase-contrast light microscopy and image analysis. Two germination phases were investigated. The length of the time period before a change in phase brightness was evident and the duration of the phase intensity change until a constant greylevel was maintained. The incubation temperature (37 and 20 degrees C) and heat activation (10 min at 65 degrees C) had a distinct effect on both phases. At 37 degrees C, spores of B. subtilis 604 started to show a decrease in brightness in L-alanine buffer after 3-39 min and needed 10-39 min to complete the phase change. At 20 degrees C, lag times of 10-100 min were observed and the spores needed 30-100 min to reach a constant greylevel. Heat activation and subsequently exposure to L-alanine buffer at 20 degrees C reduced the lag phase to 6-90 min and the phase change was finished after 30-60 min. Our results indicate enzymatic involvement before and during the phase intensity change of germinating spores.