UV resonance Raman spectra of bacteria, bacterial spores, protoplasts and calcium dipicolinate

Abstract

Resonance Raman spectra have been obtained with 222.65, 230.72, 242.39 and 250.96 nm excitation for Bacillus subtilis, Enterobacter cloacae, Pseudomonas fluorescens and Staphylococcus epidermids. Endospores of Bacillus cereus and protoplasts of Bacillus megaterium have been studied also. With 251 nm excitation, bacterial nucleic acid spectra are obtained selectively. Nucleic acid also strongly excited by 242 nm light while at that wavelength aromatic amino acid spectra just begin to be detected. Aromatic amino acid spectra are observed exclusively at 231 nm and appear along with some new strong nucleic acid peaks with 222 nm excitation. Calcium dipicolinate has been excited selectively in Bacillus spores at 242 nm. Large characteristic spectral differences can be explained as due to the selective excitation of various UV-absorbing cell components. Large intensity differences seen in the tryptophan-associated 1556 cm −1 peak excited at 222 and 231 nm appear to be strongly correlated with Gram type. Results suggest that UV-absorbing bacterial taxonomic markers can be selectively excited to give rise to characteristics resonance Raman bacterial spectral fingerprints which have the potential to be used as the basis for methods of rapid identification.