Chemical Composition of the Cell Wall of the H37Ra Strain of Mycobacterium tuberculosis

Abstract

The cell wall of the H37Ra strain of Mycobacterium tuberculosis was isolated and freed of extraneous noncovalently linked material by a series of extraction and enzymatic procedures. Chemical analysis of the cell wall has revealed the following composition: 22.8% amino acids, principally alanine, glutamate, and diaminopimelate in a molar ratio of 1:1.8:0.8; 24.7% reducing sugars, all in the form of arabinose and galactose in a molar ratio of 2.6:1; and 3.95% amino sugars, all in the form of glucosamine, muramic acid, and galactosamine in a molar ratio of 1:6.6:0.8. About 32.1% of the dry weight of the cell wall is lipid, of this about 55% is in the form of two series of mycolic acids. Each series of mycolic acids contains two homologues differing by 28 mass units. One pair of homologues contains in each a carbonyl function and an unsaturated double bond; the other pair contains two cyclopropane groups in each homologue. The remaining lipids are composed principally of normal saturated fatty acids, including tuberculostearic acid.