The cell surface of the mesophilic eubacterium Bacillus alvei CCM 2051 is covered by an oblique arranged surface layer glycoprotein. The subunits revealed by sodium dodecyl sulfate - polyacrylamide gel electrophoresis were distinct bands of molecular masses 140,000, 128,000, and 127,000. Proteolytic degradation of the purified S-layer glycoprotein yielded a single glycopeptide fraction with an apparent molecular mass of ca. 25,000. Methylation analysis in conjunction with two-dimensional nuclear magnetic resonance experiments at 500 MHz established the branched trisaccharide (formula; see text) as the repeating unit for this glycan chain.