UV Raman spectral intensities of E. coli and other bacteria excited at 228.9, 244.0, and 248.2 nm

Resonance Raman spectral intensities-per average bacterial cell have been m easured quantitatively for Gramnegative Escherichia coli, Citrobacter freun dii, and Enterobacter aerogenes; as well as Gram-positive Bacillus subtilis and Staphylococcus epidermidis. Spectra have been obtained from cultures i n the lag, log, and. stationary growth phases excited in turn by 228.9, 244 .0, and 248.2 nn light. Although Raman spectral peak positions (cm-l) excit ed by a given wavelength are very similar for all five bacterial species, t he organisms are characterized by significantly different spectral intensit y values. Intensity changes are associated with growth phase changes in all of the species as well. A comparison of measured with estimated average in tensities has been made for spectra of log-phase E. coli. It is possible to compare measured intensities with intensities estimated for log-phase E, c oli on the basis of the knowledge of its known average cellular molecular c omposition. A significant degree of hypochromism is observed in E. coli nuc leic acid spectra. In contrast strong average hyperchromism characterizes a ll aromatic amino acid peaks belonging to the same E. coli cells. Results s uggest that knowledge of spectral intensity values will enhance significant ly the capability to identify bacteria by means of their UV resonance Raman spectra.