Use of Fourier Transform Infrared Spectroscopy for the Classification and Identification of Bacteria of Importance to the Food Industry

The aim of this work was to use Fourier Transform Infrared Spectroscopy to characterize and identify bacteria of particular significance to the food industry. FT-IR spectroscopy is a rapid technique that can be applied to all groups of bacteria. The two objectives were to determine a suitable sampling procedure to record a spectrum and to determine a suitable statistical technique to identify characteristic regions of the spectrum associated with the genus and, potentially, the species. Pure cultures of bacteria were grown in broth, suspended in saline and dried to produce a film on a halide salt crystal. These films were then used to produce FT-IR spectra. In total, 80 spectra were recorded from seven genera, seven species and four strains of bacteria. Some of the spectra were considered to be too low in intensity to be included in statistical analysis. Data points from three specific windows of the remaining spectra were used to determine spectral distances between spectra. These spectral distances were used to perform cluster analysis using Ward\u27s method, the Complete Linkage method and the Centroid method. The statistical analysis created successful clusters for several of the species used but was inconclusive overall in being able to distinguish between spectra at the genus, species and strain level. This may be due to inconsistent growth of bacteria and insufficient manipulation of the data. This study has shown the potential for FT-IR spectroscopy to be used to identify bacteria with significance for food but further development is needed to reproduce the consistent results demonstrated in current literature