Application Note AN # 405 Infrared Spectroscopic Bacterial Spore Detection

The formation of endospores is one of the most effective survival strategies that have been discovered by microorganisms over eons. Vegetative cells start dividing asymmetrically after receiving a trigger pulse whereby the smaller part of the cell develops into forespore. The final endospore body is build of a special protective coating (the cortex) and contains a high concentration of calcium-dipicolinate as well as a low quantity of water providing a chemical environment that guaranties survival under extreme conditions. Mainly two genera of Gram-positive bacteria have perfected the mechanism of spore formation under unfavorable growth conditions: Bacillus and Clostridium. Genetic profiling using PCR techniques is commonly applied to identify characteristic DNA fragments from genes encoding a sporulation function in spore forming bacteria. Microscopic methods are also among the most often used detection and analysis tools ranging from classifications of visibly altered cell shapes to specific spore fluorescence. FT-IR spectroscopy does not only provide an easy and fast detection capability of spores and spore-formation, it also allows the classification of bacterial strains involved based on the infrared spectral profiles of the cells. This technique can be applied to spores, bacteria, and spore-containing bacteria as well as to their microcolonies. In cases where spores have been ‘weaponized’, FT-IR spectroscopy can easily identify the matrix used for this process such as clays or silica powders. This note illustrates the capabilities of FTIR spectroscopy in the field of spore analysis.