Evidence for the glycoprotein nature of the cell sheath of Methanosaeta-like cells in the culture of Methanothrix soehngenii strain FE

The resilient of Methanothrix soehngenii strain FE was isolated. It contained carbohydrates (7%), mainly rhamnose, ribose, and fucose, which could be specifically liberated by alkaline hydrolysis or hydrazinolysis. Four oligosaccharide-containing fractions were separated; the two major fractions corresponded to large glycans composed of 15–30 residues. The whole sheath preparation was soluble in anhydrous hydrazine. A mild hydrazinolysis treatment led to a water-soluble glycoprotein fraction, which represented 60% of the starting material and contained 100% of the carbohydrates. These high molecular mass (> 500 kDa) glycoproteins were sensitive to pronase. Fast atom bombardment mass spectrometry analysis of the major glycopeptide fraction obtained after hydrogen fluoride treatment was in accordance with the presence of asparaginyl-rhamnose linkages on a Asn-X-Ser glycosylation site. This type of glycosidic linkage has been described previously in the surface layer of Bacillus stearothermophilus.