IR and Raman Spectroscopy for Pathogen Detection

Discrimination of Stressed and Non-Stressed Food-Related Bacteria Using Raman-Microspectroscopy

“…fluor 4358 in the range of 1100-1130 cm −1 (DNA/RNA and carbo- A closer look at the spectra reveals a few variations between the microorganisms. For example, the region between 650 cm −1 and 900 cm −1 (proteins, polysaccharides, nucleic acids) [11,25,50,59] which is distinctive for specific bacteria, shows not only differences between Bacilli and E. coli, but also variances between Bacilli. For example, the vibration in the cytochrome and DNA [43,50] region around 750 cm −1 varies slightly between Bacilli, while the vibration in the region around 890 cm −1 (protein, polysaccharide) [11,43] is more pronounced in Bacilli and the vibration in the guanine/DNA region around 665 cm −1 [43,60] is less pronounced in the other microorganisms measured.…”

“…These reactions can be studied by rapid and non-destructive vibrational spectroscopy on a microscopic level by coupling Raman or IR spectrometers with a microscopic system, as these couplings are able to study samples in the range of a few micrometers [1,[23][24][25].…”

“…While Raman spectroscopy is based on the scattering of monochromatic light and the shift in polarizability, infrared (IR) spectroscopy is based on the absorption of polychromatic infrared light and the resulting change in dipole moment [23,[25][26][27][28][29]. Certainly, IR-active vibrational modes often exhibit weak Raman signals and vice versa and so both methods provide complementary information about the molecular composition of microorganisms that thus contribute to classification [8,21,30,31].…”

“…Raman spectroscopy offers high flexibility of excitation wavelengths and sample properties and a higher spatial resolution, often at a higher cost [21,26,27,33]. A more detailed explanation of Raman and IR spectroscopy and their ability to differentiate microorganisms can be found in the literature [21,23,25,28,[34][35][36].…”