Comparison of the UV resonance Raman spectra of bacteria, bacterial cell walls, and ribosomes excited in the deep UV

Resonance Raman spectra have been obtained with 218-nm excitation for Escherichia coli and Staphylococcus epidermidis. Large intensity differences seen in the tryptophan-associated 1556-cm^-1 peak appear to be strongly related to Gram type. Unlike E. coli, S. epidermidis possess a very intense peak at 1658 cm^-1 which varies in intensity with cultural conditions. Spectra excited from E. coli and Enterobacter aerogenes with 200-nm light show peaks which strongly reflect nucleic acid composition, unlike spectra excited at 218 nm. Purified, separated ribosomes of E. coli produce spectra which are dominated by nucleic acid vibrations when excited at 242 nm, but have peaks belonging nearly exclusively to protein aromatic amino acids when excited at 222 nm. The relative weakness of bacterial RNA modes excited at 222 nm from whole cells and ribosomes is attributed to nucleic acid hypochromism.