MALDI-TOF-MS analysis of bacterial spores: wet heat-treatment as a new releasing technique for biomarkers and the influence of different experimental parameters and microbiological handling.

Short wet heat-treatment is presented as a new technique to release high-mass biomarkers to obtain strain-specific fingerprints of intact bacterial spores by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). Wet heat-treatment was applied for several minutes (3-30) by two techniques using either a screw-cap tube submerged in a glycerol bath at 120 degrees C or an Eppendorff-tube submerged in a water bath at 100 degrees C. Both techniques turned out to be successful for releasing high-mass biomarkers. The influence of different experimental parameters and microbiological handling on the peak pattern of the released high-mass biomarkers was studied. While the sporulation medium, the applied washing procedure, and the choice of matrix crucially influenced the peak pattern, other parameters like storage conditions were found to be insignificant. A protocol of optimized experimental conditions for MALDI-MS of wet heat-treated spores is presented.