The cell envelope of Mycobacterium smegmatis: cytochemistry and architectural implications

In sections stained for localizing both carbohydrates (Thiery's method) and lipids (the O.T.O. method), the cell envelope of Mycobacterium smegmatis appeared to consists of an asymmetric cytoplasmic membrane surrounded by a three-layered cell wall. The outer layer of the cytoplasmic membrane was found to contain more glycoconjugate molecules (probably phosphatidyl inositol mannosides) than the inner one. The cell wall consists of the peptidoglycan (the innermost layer) surrounded by a layer containing both arabinogalactan and mycolates (the electron-dense layer), whereas the outermost layer was unstainable. There is clearly a difficulty in reconciling such a cell wall organization with the models so far proposed.