Detection and identification of a water mixture of E. coli cells and B. subtilis spores with Raman chemical imaging microscopy

Raman spectroscopy is being evaluated as a candidate technology for waterborne pathogen detection and the fidelity of the Raman spectra of microorganisms with respect to their differentiation at the single cell level are investigated. Individual entities are investigat ed in the microscope field of view (FOV) by Raman chemical imaging microscopy (RCIM) . The size of a substance was not found to cause spectral confusion when collating individual entities in the FOV by multivariate principal components (PCA) and RCIM methods. Polystyrene (PS) beads in 1-3 micron sizes were collectively grouped t ogether by PCA. Distilled and recipe tap water matrices produced the proper identification of the PS beads throughout the FOV, and all PS beads in a FOV were grouped togeth er by PCA. A mixture of Gram-positive Bacillus atrophaeus spores and Gram-negative E. coli cells were differentiated and distinguished by RCIM. Index Headings: Raman chemical imag ing microspectroscopy; Bacillus atrophaeus ; E. coli ; Principal components analysis; Water matrix; Biological discrimination; Bacteria; Recipe tap water.