X-RAY PHOTOELECTRON-SPECTROSCOPY ANALYSIS OF WHOLE CELLS AND ISOLATEDCELL-WALLS OF GRAM-POSITIVE BACTERIA - COMPARISON WITH BIOCHEMICAL-ANALYSIS

The surface chemical composition of whole cells and isolated cell wall s of four coryneform bacteria and of a Bacillus brevis strain has been determined by X-ray photoelectron spectroscopy (XPS). The XPS data we re converted into concentrations of model compounds: peptides, polysac charides, and hydrocarbonlike compounds. The composition of the surfac e of B. brevis differed markedly from that of coryneforms: the peptide concentration was about twice higher in the former case, which is att ributed to the presence of an S-layer at the cell surface; in contrast , the surface of coryneforms was rich in hydrocarbonlike compounds (ab out 40%), which was concomitant with a high water contact angle. The p eptide surface concentration of the isolated cell walls of the five st rains deduced from XPS data fitted well with the total peptide content determined by biochemical analysis, which supports the validity of XP S to determine the overall macromolecular composition of the bacterial cell surface, Compared to biochemical analysis of isolated cell walls , XPS analysis of whole cells provides information which concerns dire ctly the cell surface (2- to 5-nm-thick layer) and is less subject to alteration via losses of cell wall constituents or contamination by in tracellular compounds.