Cell envelopes with regularly arranged surface subunits in Acinetobacter and related bacteria

Bacterial cell-envelope glycoconjugates

Prokaryotic glycosylation fulfills an important role in maintaining and protecting the structural integrity and function of the bacterial cell wall, as well as serving as a flexible adaption mechanism to evade environmental and host-induced pressure. The scope of bacterial and archaeal protein glycosylation has considerably expanded over the past decade(s), with numerous examples covering the glycosylation of flagella, pili, glycosylated enzymes, as well as surface-layer proteins. This article addresses structure, analysis, function, genetic basis, biosynthesis, and biomedical and biotechnological applications of cell-envelope glycoconjugates, S-layer glycoprotein glycans, and "nonclassical" secondary-cell wall polysaccharides. The latter group of polymers mediates the important attachment and regular orientation of the S-layer to the cell wall. The structures of these glycopolymers reveal an enormous diversity, resembling the structural variability of bacterial lipopolysaccharides and capsular polysaccharides. While most examples are presented for Gram-positive bacteria, the S-layer glycan of the Gram-negative pathogen Tannerella forsythia is also discussed. In addition, archaeal S-layer glycoproteins are briefly summarized.

Characterization of the predominant Azotobacter vinelandii envelope protein

A protein with a molecular weight of 60,000 (60K) constitutes approximately 20% of the envelope protein of Azotobacter vinelandii. This protein was removed from cells and purified from other proteins by a simple washing procedure that had no effect on cell viability. Anti-60K antiserum blocked azotophage A-22 adsorption and agglutinated both vegetative cells and cysts; ferritin-conjugated antibodies used in indirect labeling studies bound uniformly to the periphery of vegetative cells. We conclude that 60K is present on the outer surface of vegetative cells and cysts. The protein is similar to the surface protein alpha of Acinetobacter ssp. in molecular weight, reassociation characteristics, and high ratio of acidic to basic amino acids. We propose that 60K forms a layer external to the outer membrane of A. vinelandii.

Chemical composition and ultrastructure of cellular and extracellular Moraxella glucidolytica lipopolysaccharides

A cellular (LPS I) and extracellular (LPS II) lipopolysaccharide were isolated from Moraxella glucidolytica cells grown on ethanol and from the culture fluid, respectively. Both LPS were toxic when injected to mice and chick embryos. These LPS contained glucose, galactose, glucosamine, galactosamine, 2-keto-3-deoxyoctonate and lipids. By permethylation studies, glucose was found to be linked (1 lead to 6) and (1 lead to 3) in LPS I and only (1 lead to 6) in LPS II. Galactose was the terminal non-reducing sugar. Branching occurred at positions 3 and 4 of galactose residues. LPS I was rich in alpha- and beta-hydroxylauric and alpha-hydroxymyristic acids and LPS I was detoxified by mild acid and alkaline treatments. It was also dissociated by sodium deoxycholate and chromatographed on Sephadex G-75. The main fraction was reassociated by removing the surfactant by dialysis. The morphology of LPS I and LPS II was examined by electron microscopy. LPS I (original and reassociated fractions) consisted exclusively of ribbons while LPS II contained ribbons and vesicles.

Methanococcus vannielii: ultrastructure and sensitivity to detergents and antibiotics

Methanococcus vannielii is a strictly anaerobic motile coccus that possesses a tuft of flagellae. The cells are markedly sensitive to mechanical stress and are readily lysed by detergents, but the organism grows normally in media of low ionic strength. The absence of a typical cell wall, further suggested by resistance of M. vannielii to penicillin, cycloserine, and vancomycin, was confirmed by ultrastructural studies. Electron micrographs showed that the cell envelope lacks a peptidoglycan layer. On the outer surface there is a regular array of subunits similar to those of the glycoprotein envelopes of the halobacteria. However, the M. vannielii cell envelope, unlike those of the holobacteria, is unable to maintain a definite shape, and a high salt concentration is not required for its integrity.

Structure of the peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on hydrocarbons

The peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on aliphatic hydrocarbons were isolated. They contained muramic acid, glucosamine, alanine, D-glutamic acid and mesodiaminoimelic acid in a molar ratio of about 0.5:0.5:1.6:1.0:1.0 (M. glucidolytica) and 0.8:0.7:1.3:1.0:1.0 (M. lwoffi). The peptidoglycans were lysozyme-resistant. However, when treated with formanide, they could be partially degraded by lysozyme. The fragments were purified and their structure determined. In both strains, the peptide subunits consisted mainly of tripeptides (L-Ala-D-Glu-meso-DAP) and tetrapeptides (L-Ala-D-glu-meso-DAP-D-Ala), most of them being directly cross-linked. It is concluded that in both strains the primary structures of the peptidoglycans are closely related.

Effects of laboratory maintenance on the nature of surface reactive antigens of Neisseria gonorrhoeae

The extensive in vitro cultivation methods used in propagating and maintaining gonococcal cells were found to affect their virulence, antigenicity, and ultrastructure. Adapting a laboratory-maintained strain of gonococci to animal virulence resulted in two lines of pilated cells with similar colonial morphologies. The animal-adapted cells, however, had a greater amount of extracellular pili and a more prominent peptidoglycan cell wall layer. They were also more resistant to the bactericidal effects of guinea-pig complement and more reactive in macroagglutination and bactericidal tests with strain-specific gonococcal antibody. In comparative guinea-pig protection trials, formalin-fixed cells of the animal-adapted cell line were 500 times more effective as immunogens than the laboratory-maintained cell line.