Die Aminosäuresequenz des Ornithin und Lysin enthaltenden Mureins einiger Stämme von Lactobacillus bifidus aus dem Pansen /The amino acid sequence of the ornithine and lysine containing mureins of some strains of Lactobacillus bifidus isolated from rumen

Cell walls of six strains of Lactobacillus bifidus (recently classified as Bifidobacterium globosum) isolated from the rumen of sheep were isolated by lysing the cells with glass beads followed by tryptic digestion. No teichoic acid could be found. The polysaccharide consists of galactose, rhamnose and glucosamine. The murein (peptidoglycan) contains MurNAc, GlcNH2NAc, Glu, Ala, and diamino acids in a molar ratio of 1:1:1:5:1. Both diamino acids, lysine and ornithine are present. In two strains they occur in about equal amounts, while in the other four strains ornithine is predominant. The lysis of the cell walls by lysozyme resulted in a mixture of two types of muropeptides: One contains lysine, the other ornithine.The amino acid sequence was determined by analysing the oligopeptides arising during acid partial hydrolysis. It was shown, that the tetrapeptides attached to the muramic acid are equal to those of other mureins: L-Ala-γ-D-Glu-L-Lys (L-Orn) -D-Ala. Glutamic acid is probably amidated, since the total hydrolysate contained slightly more than one mole of NH3 per mole of glutamic acid. The cross-liking peptide is a tri-alanine, which is bound to the ω-aminogroup of the diamino acid of one tetrapeptid and to the C-terminal D-alanine of another. Since about 2 —4% of the alanine is N-terminal in the cell wall, 10 to 20% of the interpeptide bridges are probably not cross linked. In addition 2 — 3% of the diamino acids are ω-N-terminal and therefore not substituted by a trialanine. A small percentage of D-alanine and of the diamino acids is C-terminal. The latter indicates, that some of the peptide subunits are incomplete i.e.. the terminal D-alanine is missing.