A study of the composition and structure of the cell-wall mucopeptide of micrococcus lysodeikticus

THE ACTION OF HOT FORMAMIDE ON BACTERIAL CELL WALLS

1. The cell walls of Corynebacterium tritici contain much carbohydrate and their mucopeptide contains diaminobutyric acid instead of lysine or diaminopimelic acid. They are resistant to lysozyme. 2. The residue after extraction with hot formamide contains only about 10% less carbohydrate but is attacked by lysozyme. Lysozyme also slowly attacks cell walls treated with fluorodinitrobenzene and more rapidly cell walls that have been N-acetylated. 3. All these processes block the free gamma-amino groups of diaminobutyric acid present in the untreated cell wall. Hot formamide introduces formyl groups, as shown by its ability to make formylglycine and diformyl-lysine under the same conditions. 4. N-Formyl groups are also introduced into the cell walls of Micrococcus lysodeikticus by hot formamide, but this change increases only slightly their already great sensitivity to lysozyme. N-Acetylation also increases sensitivity to lysozyme.

The characterization of the rumen bacterium Eadie's oval, Magnoovum gen. nov. eadii sp. nov

The rumen bacterium Eadie's Oval was examined by means of cell wall analysis and biochemical tests with a view to determine its taxonomic position. The purified cell walls contained components consistent with the organism being a Gram-negative bacterium, and despite its large size no abnormal cell wall constituents were found. The biochemical tests indicate that Eadie's Oval is not a member of a previously described family. The name Magnoovum gen. nov. eadii sp. nov. is proposed.

Association of lack of cell wall teichuronic acid with formation of cell packets of Micrococcus lysodeikticus (luteus) mutants

Morphological mutants of Micrococcus lysodeikticus (luteus) were isolated by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. They occurred on plates in large, regular cell packets, whereas the parent cells usually grew as groups of two or four cells or as short chains. The mutants required a much higher concentration of Mg2+ for growth than the parent cells. The concentrations of Mg2+ and other components of the culture medium tested did not significantly affect the morphology of either the parent or mutant strains. The mutant strains were not agglutinated by antiserum to M. lysodeikticus, which mainly interacts with teichuronic acid on the cell surface, and chemical analysis of isolated cell walls of the mutants indicated the absence of teichuronic aicd. No significant differences were detected between the parent and mutant strains in the amounts of other cell wall components, e.g., peptidoglycan, protein, and teichoic acid. They possible roles of teichuronic acid in cell separation and attachment of divalent cations are discussed.

Effect of lysozyme treatment on cell wall ultrastructure in Sarcina flava

Treatment of Sarcina flava NCTC 7503 cells with lysozyme resulted in incomplete removal of the cell wall and imparted a layered appearance to it.

Determination of amino sugars in mixtures containing glucosamine, galactosamine and muramic acid

A colorimetric method is described whereby the direct quantitative determination of glucosamine, galactosamine and muramic acid can be achieved without previous treatment of the cell-wall hydrolysate, for example by column chromatography. Molar ratios of hexosamines in cell-wall preparations, from a number of bacterial species, determined by this method were found to be in general agreement with previously published results.

Reversal of the vancomycin inhibition of peptidoglycan synthesis by cell walls

Addition of cell walls to the peptidoglycan synthetase-acceptor system containing vancomycin (50 mug/ml) prevented the inhibition by the antibiotic. In addition, the inhibition of incorporation of [(14)C]muramyl-pentapeptide into peptidoglycan in the presence of vancomycin was reversed by the addition of cell walls to the assay mixture at 60 min. Cell walls previously saturated with vancomycin lost their ability to reverse the inhibition by the antibiotic. The inhibition of peptidoglycan synthesis by ristocetin was partially reversed by the addition of cell walls. The initial stage in peptidoglycan synthesis is catalyzed by phospho-N-acetyl(NAc)muramyl-pentapeptide translocase (uridine 5'-phosphate) according to the reaction: UDP-NAc-muramyl-pentapeptide + acceptor right arrow over left arrow acceptor-phospho-NAc-muramyl-pentapeptide + UMP where acceptor is C(55)-isoprenoid alcohol phosphate. Vancomycin stimulates the transfer of phospho-NAc-muramyl-pentapeptide to the acceptor, and the addition of cell walls to this assay mixture prevented the stimulation of transfer. In addition to the transfer reaction, the enzyme catalyzes the exchange of [(3)H]uridine monophosphate (UMP) with UDP-NAc-muramyl-pentapeptide. The exchange reaction is effectively inhibited by vancomycin. For example, 60 mug of vancomycin per ml inhibited the rate of exchange by 50%. Addition of cell walls restored the exchange of UMP with the UMP moiety of UDP-NAc-muramyl-pentapeptide. Thus, cell walls appeared to have a higher affinity for vancomycin than did either the peptidoglycan synthetase-acceptor system or phospho-NAc-muramyl-pentapeptide translocase. These results provide support for the proposal made by Best and Durham that the effective binding of vancomycin to the cell wall could result in the inhibition of transfer of membrane-associated peptidoglycan chains to the growing wall.

Passive electrical properties of microorganisms. 3. Conductivity of isolated bacterial cell walls

The dielectric properties of isolated Micrococcus lysodeikticus cell walls have been studied to establish more firmly the view that wall-associated ions play a major role in the conduction of low frequency electric current by intact bacterial cells. The conductivity of isolated walls was found to be about 0.40 mho/m. If counterions associated with fixed, ionized groups in the wall have average mobilities equal to that of sodium ions in free solution, the fixed charge concentration required to account for the measured conductivity is between 75 and 95 meq/liter of wet wall volume. Estimates of the numbers of titratable amino and carboxyl groups in wall polymers indicate that conductivity is more closely related to net wall charge than to total wall charge. The measured wall conductivity was used to predict a value of 0.15 +/- 0.03 mho/m for whole cell conductivity. This prediction is close to the measured value of 0.25 +/- 0.05 mho/m and it is thought that much of the disparity in values is related to changes in wall structure and composition during the isolation procedures.

The cell wall of Bacillus licheniformis N.C.T.C. 6346. Composition of the mucopeptide component

1. The mucopeptide component of wall preparations from Bacillus licheniformis was obtained in soluble form by treatment of the acid-insoluble residue of walls with lysozyme. 2. The soluble mucopeptide contains glutamic acid, diaminopimelic acid, alanine, N-acetylglucosamine and N-acetylmuramic acid in the molecular proportions 1.0:1.0:1.6:0.8:0.7. In addition approx. 1 mole of amide/mole of glutamic acid is present. Essentially all of the dry weight and nitrogen content of soluble mucopeptide is accounted for by these constituents. 3. The optical configurations of the amino acids were determined. Approx. 0.6 mole of d-alanine and 1.0 mole of l-alanine are present/mole of glutamic acid. 4. The structures of several small peptides derived from soluble mucopeptide after mild acid hydrolysis were established. 5. The structure of soluble mucopeptide from B. licheniformis is discussed on the basis of these results together with data on the number of free amino groups present in soluble mucopeptide.

Components of the cell wall of Clostridium welchii (type A)

1. The cell wall of Clostridium welchii (type A) contains alanine, 2,6-diaminopimelic acid, glutamic acid, glycine, glucosamine, muramic acid, galactosamine, mannosamine, ethanolamine, rhamnose, galactose and phosphorus. 2. Heating with formamide at 150 degrees resolved the wall into a formamide-soluble polysaccharide fraction and a formamide-insoluble mucopeptide fraction. 3. The formamide-soluble fraction contained two components: an electrophoretically neutral polysaccharide made up of galactose, rhamnose, galactosamine and phosphorus and an electrophoretically acidic polymer containing mannosamine, ethanolamine and phosphorus. 4. The formamide-insoluble residue has been digested by lysozyme to give soluble fragments of high molecular weight. 5. All fractions contain an unknown ethyl acetate-extractable substance that can be oxidized by sodium metaperiodate. 6. The amino acid compositions of the fragments produced by lysozyme are compatible with a mucopeptide structure which has cross bridges containing all of the constituent amino acids.

Properties of the polysaccharide and mucopeptide components of the cell wall of Lactobacillus casei

1. The polysaccharide and mucopeptide components of the cell wall of Lactobacillus casei have been separated by mild conditions of acid hydrolysis. 2. Removal of the polysaccharide renders the mucopeptide susceptible to lysozyme. 3. The mucopeptide and polysaccharide components have been analysed and the results compared with those obtained previously. 4. The polysaccharides responsible for group specificity have a terminal reducing N-acetylgalactosamine residue substituted on C((3)) by the adjacent sugar; estimation of this component gave an indication of the molecular weight of the polysaccharides. 5. Evidence has been obtained for the presence of rhamnosyl-(1-->3)-N-acetylgalactosamine among the products of acid hydrolysis of the group B polysaccharide.

ACRIDINE ORANGE BINDING BY MICROCOCCUS LYSODEIKTICUS

Beers, Roland F., Jr. (Johns Hopkins University, Baltimore, Md). Acridine orange binding by Micrococcus lysodeikticus . J. Bacteriol. 88: 1249–1256. 1964.— Micrococcus lysodeikticus cells bind acridine orange (AO) reversibly. The adsorption isotherm is consistent with a highly cooperative-type binding similar to that observed with polyadenylic acid. The cells exhibit a strong buffering action on the concentration of free AO which remains constant (1 μg/ml) over a range from 5 to 95% saturation of the cells by AO. The cells stain either fluorescent orange or green. The fraction stained orange is directly proportional to the quantity of dye adsorbed, indicating that these cells bind a fixed amount of AO (10% of dry weight). The green-stained cells contain less than 1% of the AO bound to orange-stained cells. The results suggest that the abrupt increase in amount of AO bound by the orange-stained cells occurs when the concentration of free AO reaches a threshold concentration. Similar results were obtained with Bacillus cereus . Mg increases the free AO concentration and the extent of binding capacity of the cells.