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PubMed1968

Isolation and chemical structure of the peptidoglycan of Spirillum serpens cell walls.

The peptidoglycan layer of Spirillum serpens cell walls was isolated from intact cells after treatment with sodium dodecylsulfate and digestion with Pronase. The isolated peptidoglycan contained glucosamine, muramic acid, alanine, glutamic acid, and meso-diaminopimelic acid in the approximate molar ratio of 1:1:2:1:1. Aspartic acid and glycine were the only other amino acids found in significant quantities. N-terminal amino acid analyses of the tetrapeptide amino acids in the peptidoglycan revealed that 54% of the diaminopimelic acid molecules are involved in cross-linkage between tetrapeptides. This amount of cross-linkage is greater than that found in the peptidoglycan of previously studied cell walls of gram-negative bacteria. The polysaccharide backbone was isolated, after myxobacter AL-1 enzyme digestion of the peptidoglycan, by fractionation with ECTEOLA-cellulose and Sephadex G-100. An average length of 99 hexosamines for the polysaccharide chains was found (ratio of total hexosamines to reducing end groups).

Amino Acids↗
PubMed1968

Peptidoglycan of Myxococcus xanthus: structure and relation to morphogenesis.

The chemical nature and distribution of the peptidoglycan in Myxococcus xanthus at various stages of the cellular life cycle were investigated. Vegetative cells and microcysts contained approximately 0.6% by weight of peptidoglycan. The overall composition of the peptidoglycan was similar in both cell types and was approximately 1 glutamic acid, 1 diaminopimelic acid, 1.7 alanine, 0.75 N-acetylglucosamine, and 0.75 N-acetylmuramic acid. (We have assumed that all the hexosamines are N-acetylated.) The sizes of the subunits (estimated by gel filtration) solubilized by muramidases were considerably larger (tetramer and oligomer) in the microcysts than in the vegetative cells (mostly dimer). There was a transient decrease in cross-linking (measured as an increase in the amount of free amino group of diaminopimelic acid) during the stage of microcyst formation when the cells converted from ovoids to spheres. At the same time, there occurred a large and rapid increase in a galactosamine derivative which may have reflected the synthesis of capsular material. Immediately prior to this period of morphogenesis, the cells became resistant to penicillin but remained sensitive to d-cycloserine. The walls of vegetative cells were completely disaggregated by trypsin and sodium lauryl sulfate, suggesting a discontinuous peptidoglycan layer. This was no longer apparent after the ovoid-sphere stage of microcyst formation. The relationship to morphogenesis of the chemical changes in the cell wall is discussed.

Amino Acids↗
PubMed1965

An extracellular glycolipid produced by Escherichia coli grown under lysine-limiting conditions.

1. Some of the products excreted by cultures of lysine-requiring Escherichia coli A.T.C.C. 12408 grown under lysine-limiting conditions have been studied. 2. A glycolipid designated ;extracellular lipoglycopeptide' was prepared from culture filtrates of such organisms. It contained 35% of lipid, 19% of carbohydrate, 3.4% of P and 3.7% of N. 3. Comparison of the lipids, fatty acids, carbohydrates and amino acids of this lipoglycopeptide with those of whole cells, cell walls and cellular lipopolysaccharides shows that it has few features (except its residual lipids) in common with any of these fractions. 4. The lipoglycopeptide was antigenically related to both walls and lipopolysaccharide.

Amino Acids↗
PubMed1970

Chemical composition of the cell wall of the H37Ra strain of Mycobacterium tuberculosis.

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.

Alanine↗