Localization of the attachment site of oligoglucans to Mesorhizobium loti HAMBI 1148 murein.

Abstract

The location and nature of the linkage between peptidoglycan and oligoglucans in the cell wall of Mesorhizobium loti HAMBI 1148 have been defined by the analysis of nitrous acid deamination of peptidoglycan glucosaminyl residues. The MurNH(2)-Glc(n) fraction was obtained after converting deaminoacylated and N-deacetylated muramyl residues in the cell wall preparation to lactam forms which were stable during subsequent deamination, followed by reduction and opening of the lactams. GC/MS analysis of this material, subjected to partial hydrolysis and reduction or to methanolysis followed by peracetylation, confirmed the presence of glucosyl residues glycosidically attached to muramic acid. The MALDI-TOF spectroscopic analysis of the deaminated material also revealed the presence of [M-H](-) or [M+Na-2H](-) ions representing fragments containing muramic acid with one to three linked glucose residues. The analysis of fully methylated neutral oligosaccharides released from the peptidoglycan with lysozyme followed by borohydride reduction showed the presence of di- and trisaccharides lacking the reducing end.