ToF-SIMS studies as a tool to discriminate between spores and vegetative cells of bacteria

Within the field of microbiology rapid bacterial identification is a subject of growing interest. Research into food borne pathogens and disease causing bacteria as well as dormant bacterial spores has highlighted the need for new, sensitive and rapid diagnostic tools to avoid human health risks. In this work we investigate the application of TOF-SIMS for the discrimination between spores and vegetative bacterial cells of Bacillus megaterium. A custom-built imaging ToF-SIMS equipped with polyatomic ion sources (Au-n(+), and C-60(+)) and an in situ freeze-fracture stage was used for the analysis of spore and vegetative cell samples. The study assesses the suitability of ToF-SIMS analysis in combination with computatorial methods (principal component analysis and variance analysis) for the discrimination between bacterial spores and vegetative cells. We demonstrate that the combination of the two methods gives a tentative identification of surface phospholipids of spores and vegetative cells and that differences in the phospholipid pattern between spore samples and vegetative cells can be highlighted. The method is especially useful in the determination of phospholipids with higher abundance in spores (diglyceryldiacylglycerols and cardiolipins). The possible use of ToF-SIMS analysis as a tool for the rapid detection of bacterial spores in food samples or tap water is discussed. (C) 2004 Elsevier B.V. All rights reserved.