X-ray Photoelectron-spectroscopy and Biochemical-analysis of the Surface of Lactobacillus-helveticus Atcc-12046

The cell wall of Lactobacillus helveticus ATCC 12046 was investigated: intact cells were compared to cells stripped of their surface layer (S-layer) by treatment with LiCl. The protein profile and the amino acid composition of isolated cell walls were compared with those of LiCl-treated walls. The S-layer-forming-protein was tested for the presence of glycosidic residues. Finally, the overall elemental composition of the surface of intact cells, LiCl-treated cells and isolated S-layer-forming-protein was determined by X-ray photoelectron spectroscopy. The data collected by the ensemble of methods employed indicate that the surface of intact cells consists mainly of proteins. with some polysaccharides and teichoic or lipoteichoic acids. The exposed surface of LiCl-treated bacteria is rich in peptidoglycan, teichoic acids (or lipoteichoic acids) and polysaccharide. The extracted material is practically pure protein with traces of some glycosidic residues.