A polymer of N-acetylglucosamine 1-phosphate in the wall of Staphylococcus lactis 2102

Sec-secretion and sortase-mediated anchoring of proteins in Gram-positive bacteria

Signal peptide-driven secretion of precursor proteins directs polypeptides across the plasma membrane of bacteria. Two pathways, Sec- and SRP-dependent, converge at the SecYEG translocon to thread unfolded precursor proteins across the membrane, whereas folded preproteins are routed via the Tat secretion pathway. Gram-positive bacteria lack an outer membrane and are surrounded by a rigid layer of peptidoglycan. Interactions with their environment are mediated by proteins that are retained in the cell wall, often through covalent attachment to the peptidoglycan. In this review, we describe the mechanisms for both Sec-dependent secretion and sortase-dependent assembly of proteins in the envelope of Gram-positive bacteria. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.

Natural phosphoglycans containing glycosyl phosphate units: structural diversity and chemical synthesis

An anomeric phosphodiester linkage formed by a glycosyl phosphate unit and a hydroxyl group of another monosaccharide is found in many glycopolymers of the outer membrane in bacteria (e.g., capsular polysaccharides and lipopolysaccharides), yeasts and protozoa. The polymers (phosphoglycans) composed of glycosyl phosphate (or oligoglycosyl phosphate) repeating units could be chemically classified as poly(glycosyl phosphates). Their importance as immunologically active components of the cell wall and/or capsule of numerous microorganisms upholds the need to develop routes for the chemical preparation of these biopolymers. In this paper, we (1) present a review of the primary structures (known to date) of natural phosphoglycans from various sources, which contain glycosyl phosphate units, and (2) discuss different approaches and recent achievements in the synthesis of glycosyl phosphosaccharides and poly(glycosyl phosphates).

Excretion of a phosphorus-containing carbohydrate by Streptomyces sp. A50

A new phosphorus-containing compound (1) was detected by (31)P NMR spectroscopy in Streptomyces sp. A50. Compound 1, 1(alpha)-O-methyl-2-(N-acetyl)glucoseamine-6-O-phosphate-1(alpha)-2-(N-acetyl)glucosamine, exhibited a pK(a) value around zero. The compound was found both in the extracellular culture broth and in the cells. While very low concentrations of 1 were found in the culture broth of other species of Streptomyces, its presence in high concentrations was specific to Streptomyces sp. A50. The highly acidic compound was isolated from the broth, and its structure was elucidated by a combination of 1D-, 2D-homonuclear, and inverse heteronuclear NMR techniques and mass spectroscopy.

Molecular analysis of the tagF gene, encoding CDP-Glycerol:Poly(glycerophosphate) glycerophosphotransferase of Staphylococcus epidermidis ATCC 14990

Staphylococcus epidermidis ATCC 14990 produces a wall-associated glycerol teichoic acid which is chemically identical to the major wall-associated teichoic acid of Bacillus subtilis 168. The S. epidermidis tagF gene was cloned from genomic DNA and sequenced. When introduced on a plasmid vector into B. subtilis 1A486 carrying the conditionally lethal temperature-sensitive mutation tagF1 (rodC1), it expressed an 85-kDa protein which allowed colonies to grow at the restrictive temperature. This showed that the cloned S. epidermidis gene encodes a functional CDP-glycerol:poly(glycerophosphate) glycerophosphotransferase. An amino acid substitution at residue 616 in the recombinant TagF protein eliminated complementation. Unlike B. subtilis, where the tagF gene is part of the tagDEF operon, the tagF gene of S. epidermidis is not linked to any other tag genes. We attempted to disrupt the chromosomal tagF gene in S. epidermidis TU3298 by directed integration of a temperature-sensitive plasmid but this failed, whereas a control plasmid containing the 5' end of tagF on a similarly sized DNA fragment was able to integrate. This suggests that the tagF gene is essential and that the TagF and other enzymes involved in teichoic acid biosynthesis could be targets for new antistaphylococcal drugs.

Structural studies on the linkage unit between poly(N-acetylglucosamine 1-phosphate) and peptidoglycan in cell walls of Bacillus pumilus AHU 1650

Structural studies were carried out on the polymer chains and their linkage regions in two kinds of teichoic acids, poly(N-acetylglucosamine 1-phosphate) [poly(GlcNAc-1-P)] and glycerol teichoic acid, bound to peptidoglycan in the cell walls of Bacillus pumilus AHU 1650. The poly(GlcNAc-1-P)-glycan complex isolated from lysozyme digests of the cell walls contained mannosamine and glycerol as minor components. On the basis of proton NMR spectroscopic data and isolation of N-acetylglucosamine 4-phosphate from acid hydrolysates, the poly(GlcNAc-1-P) was shown to be a polymer in which N-acetylglucosamine 1-phosphate units are joined at C-4 of the glucosamine residues. Mild alkaline hydrolysis of the poly(GlcNAc-1-P)-glycan complex gave a mannosamine-linked glycan fragment and the acidic polymer fraction that contained glycerol residues. Mild acid treatment of the mannosamine-linked glycan fragment gave the linkage disaccharide, ManNAc(beta 1----4)GlcNAc, whereas the acidic polymer fraction was degraded by this treatment into N-acetylglucosamine 4-phosphate and a glycerol-containing fragment characterized as P-(Gro-P)7 (Gro = glycerol). On the other hand, direct mild acid hydrolysis of the complex gave a fragment characterized as P-(Gro-P)7-ManNAc(beta 1----4)GlcNAc. These results lead to a conclusion that in the cell walls the poly(GlcNAc-1-P) chain is attached to peptidoglycan through a linkage unit, (Gro-P)7-ManNAc(beta 1----4)GlcNAc. By means of similar procedures, it was shown that the other cell wall polymer, glycerol teichoic acid, is also attached to peptidoglycan through the same disaccharide, ManNAc(beta 1----4)GlcNAc.

Chemical composition and structure of cell wall teichoic acids of staphylococci

The cell wall teichoic acid structures of 22 staphylococci including 13 type strains were determined. Most of the strains contain a poly(polyolphosphate) teichoic acid with glycerol and/or ribitol as polyol component. The polyolphosphate backbone is partially substituted with various combinations of sugars and/or amino sugars. Most of the substituents occur in a monomeric form but some strains also contain dimers of N-acetylglucosamine as substituents. Staphylococcus hyicus subsp. hyicus NCTC 10350 and S. sciuri DSM 20352 revealed rather complex cell wall teichoic acids. They consist of repeating sequences of phosphate-glycerol-phosphate-N-acetylglucosamine. The amino sugar component is present in this case as a monomer or an oligomer (n less than or equal to 3). Moreover, the glycerol residues are partially substituted with N-acetylglucosamine. The cell wall teichoic acid of S. auricularis is a poly(N-acetylglucosaminyl-phosphate) polymer similar to that found in S. caseolyticus ATCC29750. The cell wall teichoic acid structures for type strains of S. auricularis, S. capitis, S. cohnii, S. haemolyticus, S. hominis, S. hyicus subsp. hyicus, S. sciuri, S. xylosus and S. warneri were determined for the first time in detail. The structures of some of the previously described teichoic acids had to be revised (S. epidermidis, S. simulans, S. aureus phage type 187).

The enzymic synthesis of beta-[32P]UDP-N-acetylglucosamine

Cells of Micrococcus sp. 2102 incorporate inorganic [32P]phosphate from the medium into the sugar-phosphate polymer of the wall. Controlled acid hydrolysis of sodium dodecyl sulphate-extracted cells gives N-acetylglucosamine 6-[32P]-phosphate which can be purified by ion-exchange chromatography and incubated with UTP in the presence of crude preparations of phosphoacetylglucosamine mutase from Neurospora crassa and UTP:N-acetylglucosamine 1-phosphate phosphotransferase from Bacillus licheniformis which act in concert to synthesise beta-[32P]UDP-N-acetylglucosamine.

The linkage of sugar phosphate polymer to peptidoglycan in walls of Micrococcus sp. 2102

1. Protein-free walls of Micrococcus sp. 2102 contain peptidoglycan, poly-(N-acetylglucosamine 1-phosphate) and small amounts of glycerol phosphate. 2. After destruction of the poly-(N-acetylglucosamine 1-phosphate) with periodate, the glycerol phosphate remains attached to the wall, but can be removed by controlled alkaline hydrolysis. The homogeneous product comprises a chain of three glycerol phosphates and an additional phosphate residue. 3. The poly-(N-acetylglucosamine 1-phosphate) is attached through its terminal phosphate to one end of the tri(glycerol phosphate). 4. The other end of the glycerol phosphate trimer is attached through its terminal phosphate to the 3-or 4-position of an N-acetylglucosamine. It is concluded that the sequence of residues in the sugar 1-phosphate polymer-peptidoglycan complex is: (N-acetylglucosamine 1-phosphate)24-(glycerol phosphate)3-N-acetylglucosamine 1-phosphate-muramic acid (in peptidoglycan). Thus in this organism the phosphorylated wall polymer is attached to the peptidoglycan of the wall through a linkage unit comprising a chain of three glycerol phosphate residues and an N-acetylglucosamine 1-phosphate, similar to or identical with the linkage unit in Staphylococcus aureus H.

Binding of magnesium ions to cell walls of Bacillus subtilis W23 containing teichoic acid or teichuronic acid

When grown in a chemostat under various nutritional conditions, cells of Bacillus subtilis W23 produce walls containing teichoic acid or teichuronic acid. The binding of Mg2+ to these walls and to the isolated anionic polymers in solution was measured by equilibrium dialysis. In solution the ribitol teichoic acid bound Mg2+ in the molar ratio Mg2+/P=1:1 with an apparent association constant (Kassoc.) of 0.61 X 10(3)M-1, and the teichuronic acid bound Mg2+ in the ratio Mg2+/CO2-=1.1, Kassoc.=0.3 X 10(3)M-1. Cell walls containing teichuronic acid exhibited closely similar binding properties to those containing teichoic acid; in both cases Mg2+ was bound in the ratio Mg/P or Mg/CO2- of 0.5:1 and with a greater affinity than displayed by the isolated polymers in solution. It was concluded that Mg2+ ions are bound bivalently between anionic centres in the walls and that the incorporation of teichoic acid or teichuronic acid into the walls gives rise to similar ion-binding and charged properties. The results are discussed in relation to the possible functions of anionic polymers in cell walls.

Bacterial precipitins and their immunoglobulin class in atopic asthma, non-atopic asthma, and chronic bronchitis

In a study of groups of patients with atopic (extrinsic) asthma, non-atopic (intrinsic) asthma, and chronic bronchitis, no difference could be detected in the numbers having precipitating antibodies against species specific antigens from Staphylococcus aureus or Streptococcus pneumoniae compared to suitably matched control subjects. Precipitating antibodies against species specific antigens from Haemophilus influenzae, demonstrated in this investigation by double diffusion in agar gel, were found much more frequently in patients with chronic mucopurulent or obstructive bronchitis (50%) than in either asthmatic subjects (6%) or normal controls (6%) (P = less than 0.0005). While the precipitating antibody demonstrated in these patients against the extracts of Str. pneumoniae and Staph. aureus was in the IgG class alone, IgM and IgA antibody were detected against the species specific but not the non-species specific antigens of H. influenzae. These results underline the importance of H. influenzae as an infecting agent in chronic bronchitis and suggest that the finding of precipitins against the species specific H1 and H2 antigens of this bacterium denotes infection either concurrently or in the recent past. There is no evidence to suggest from this study that infection with Staph. aureus, Str. pneumoniae or H. influenzae is any more common in asthmatics as a group compared to controls or between patients with the non-atopic (intrinsic) and atopic (extrinsic) form of the disease.

Bacteriophage SP50 as a marker for cell wall growth in Bacillus subtilis

When grown under conditions of phosphate limitation, Bacillus subtilis W23 lacked wall teichoic acid and did not adsorb phage SP50. During transition from growth under conditions of phosphate limitation to those of potassium limitation, the bacteria developed an ability to adsorb phage which increased exponentially in relation to their content of wall teichoic acid. During transition in the reverse direction, the bacteria retained near-maximum phage-binding properties until their content of wall teichoic acid had fallen to a fairly low level. These observations suggest that newly incorporated wall material does not immediately appear at the cell surface in a structure to which phage can adsorb. Examination of the location of adsorbed phage particles showed that recently incorporated receptor material appeared at the cell surface first along the length of the cylindrical portion of the cell. The results are consistent with models of wall assembly in which newly synthesized wall material is intercalated at a large number of sites that are distributed along the length of the cell. This newly incorporated material may be located initially at a level underlying the surface of the cell and may become exposed at the surface only during subsequent growth. Incorporation of new material may also proceed rapidly into the developing septa, but new wall material is incorporated into existing polar caps more slowly, or perhaps not at all.

Poly(glucosylglycerol phosphate) teichoic acid in the walls of Bacillus stearothermophilus B65

1. Walls of Bacillus stearothermophilus B65 contain a glycerol teichoic acid in which repeating structures consisting of 1-O-alpha-D-glucopyranosylglycerol phosphate are held together by phosphodiester linkage between the glycerol and glucose moieties of adjacent units. 2. The walls are not agglutinated on incubation with concanavalin A, nor does the isolated teichoic acid form a precipitate with this lectin. 3. No evidence was obtained of the presence of the glucosylated (1 leads to 2)-poly(glycerol phosphate) teichoic acid which has previously been reported to occur in walls of this bacterium.

Studies on the linkage between teichoic acid and peptidoglycan in a bacteriophage-resistant mutant of Staphylococcus aureus H

1. In addition to poly(ribitol phosphate) the walls of a bacteriophage-resistant mutant of Staphylococcus aureus H contain glycerol phosphate residues that are not removed on digestion with trypsin or extraction with phenol. 2. The glycerol phosphate is present in a chain, containing three or four glycerol phosphate residues, which is covalently attached to the peptidoglycan through a phosphodiester linkage to muramic acid; this linkage is readily hydrolysed by dilute alkali. 3. The degradative studies described suggest that the poly(ribitol phosphate) chains of the wall teichoic acid may be attached to the wall by linkage to this glycerol phosphate oligomer.

The teichuronic acid of cell walls of Bacillus subtilis W23 grown in a chemostat under phosphate limitation

Cell walls of Bacillus subtilis W23 contain teichuronic acid when grown in a chemostat under phosphate limitation at a low dilution rate, but teichoic acid at a higher dilution rate. The teichuronic acid was purified and shown to be a polymer of glucuronic acid and N-acetylgalactosamine.

Extraction and purification of lipoteichoic acids from Gram-positive bacteria

Hot and cold, 80% aqueous phenol extraction procedures together with an aqueous extraction technique have been evaluated for the isolation of lipoteichoic acids from the cytoplasmic membrane of Gram-positive bacteria. Lipoteichoic acids of Staphlococcus aureus H, Micrococcus 2102, Baccillus subtilis 168, and Bacillus subtilis W-23 were examined as each of them emphasises a different problem of contamination. The purity of the lipoteichoic acids with respect to cell-wall material, nucleic acid, and protein is discussed together with the criteria of purity which enables critical structural analysis of lipoteichoic acids to be carried out.