Proteins and dipicolinic acid released during heat shock activation of Bacillus subtilis spores probed by optical spectroscopy

UV fluorescence and absorption spectroscopy from Bacillus subtilis spores detected proteins and dipicolinic acid (DPA) released into the supernatant after heat treatments ranging from 20(degree) to 90 (degree)C. The protein and DPA concentration in the supernatant was greater with higher heat treatment temperatures, undergoing a substantial increase for T >= 60 (degree)C, and supporting the theory that spores undergo a phase transition from a glassylike to a rubberylike state at 56 (degree)C. Gel electrophoresis detected several small proteins with molecular weights between 6 and 11 kDa. These proteins may be small acid-soluble spore proteins that are present in spores but break down during germination. A 30 kDa protein extracted above 60 (degree)C is related to the rubber-glass phase transition.