Composition and properties of the cell wall of Methanospirillum hungatii

Dithiothreitol reacted, at pH 9.0, with the isolated cell walls of Methanospirillum hungatii, to release about 23% of the cell wall dry weight as a high molecular weight fraction (> 0.5 million daltons). Untreated walls consisted of 70% amino acids, 11% lipid, and 6.6% carbohydrate. Sugars were identified as rhamnose, ribose, glucose, galactose, and mannose. The wall material that was released contained only 47% amino acids and was enriched in lipid, glucose, and phosphate. These results support data from electron micrographs, showing the localized release of cell wall material by the disulfide bond-breaking reagent at alkaline pH. In amino acid composition the untreated walls did not differ greatly from the material released by dithiothreitol, but differed considerably from the walls of another strain of M. hungatii. The ratios of the amino acids found in the cell wall proteins of several archaebacteria and of Bacillus cereus spore coats were similar.