Characterization of the linkage between the type III capsular polysaccharide and the bacterial cell wall of group B Streptococcus

The capsular polysaccharide of group B Streptococcus is a key virulence factor and an important target for protective immune responses. Until now, the nature of the attachment between the capsular polysaccharide and the bacterial cell has been poorly defined. We isolated insoluble cell wall fragments from lysates of type III group B Streptococcus and showed that the complexes contained both capsular polysaccharide and group B carbohydrate covalently bound to peptidoglycan. Treatment with the endo-N-acetylmuramidase mutanolysin released soluble complexes of capsular polysaccharide linked to group B carbohydrate by peptidoglycan fragments. Capsular polysaccharide could be enzymatically cleaved from group B carbohydrate by treatment of the soluble complexes with beta-N-acetylglucosaminidase, which catalyzes hydrolysis of the beta-D-GlcNAc(1-->4)beta-D-MurNAc subunit produced by mutanolysin digestion of peptidoglycan. Evidence from gas chromatography/mass spectrometry and (31)P NMR analysis of the separated polysaccharides supports a model of the group B Streptococcus cell surface in which the group B carbohydrate and the capsular polysaccharide are independently linked to the glycan backbone of cell wall peptidoglycan; group B carbohydrate is linked to N-acetylmuramic acid, and capsular polysaccharide is linked via a phosphodiester bond and an oligosaccharide linker to N-acetylglucosamine.     

Biochemical and immunochemical properties of the cell surface of Renibacterium salmoninarum.

The biochemical composition of the cell envelope of Renibacterium salmoninarum was investigated in a total of 13 strains isolated from different salmonid fish species at various geographical locations of the United States, Canada, and Europe. A marked similarity with the type strain R. salmoninarum ATCC 33209 was found both in the peptidoglycan and the cell wall polysaccharide. The primary structure of the peptidoglycan was found to be consistent with lysine in the third position of the peptide subunit, a glycyl-alanine interpeptide bridge between lysine and D-alanine of adjacent peptide subunits, and a D-alanine amide substituent at the alpha-carboxyl group of D-glutamic acid in position 2 of the peptide subunit. The cell wall polysaccharide contained galactose as the major sugar component which was accompanied by rhamnose, N-acetylglucosamine, and N-acetylfucosamine. The polysaccharide amounted to more than 60% of the dry weight of the cell walls. It was found to be covalently linked to the peptidoglycan and was released by hot formamide treatment. On gel filtration chromatography the extracted polysaccharide behaved like a homogeneous polymeric compound. The purified cell wall polysaccharide showed antigenic activity with antiserum obtained by immunization of rabbits with heat-inactivated trypsinized cells of R. salmoninarum. Immunoblotting experiments with nontrypsinized cell walls and antisera raised against R. salmoninarum cells revealed that antigenic proteins were attached to the cell walls.     

Clopidogrel, a P2Y12 receptor antagonist, potentiates the inflammatory response in a rat model of peptidoglycan polysaccharide-induced arthritis

The P2Y12 receptor plays a crucial role in the regulation of platelet activation by several agonists, which is irreversibly antagonized by the active metabolite of clopidogrel, a widely used anti-thrombotic drug. In this study, we investigated whether reduction of platelet reactivity leads to reduced inflammatory responses using a rat model of erosive arthritis. We evaluated the effect of clopidogrel on inflammation in Lewis rats in a peptidoglycan polysaccharide (PG-PS)-induced arthritis model with four groups of rats: 1) untreated, 2) clopidogrel-treated, 3) PG-PS-induced, and 4) PG-PS-induced and clopidogrel-treated. There were significant differences between the PG-PS+clopidogrel group when compared to the PG-PS group including: increased joint diameter and clinical manifestations of inflammation, elevated plasma levels of pro-inflammatory cytokines (IL-1 beta, interferon (IFN) gamma, and IL-6), an elevated neutrophil blood count and an increased circulating platelet count. Plasma levels of IL-10 were significantly lower in the PG-PS+clopidogrel group compared to the PG-PS group. Plasma levels of platelet factor 4 (PF4) were elevated in both the PG-PS and the PG-PS+clopidogrel groups, however PF4 levels showed no difference upon clopidogrel treatment, suggesting that the pro- inflammatory effect of clopidogrel may be due to its action on cells other than platelets. Histology indicated an increase in leukocyte infiltration at the inflammatory area of the joint, increased pannus formation, blood vessel proliferation, subsynovial fibrosis and cartilage erosion upon treatment with clopidogrel in PG-PS-induced arthritis animals. In summary, animals treated with clopidogrel showed a pro-inflammatory effect in the PG-PS-induced arthritis animal model, which might not be mediated by platelets. Elucidation of the mechanism of clopidogrel-induced cell responses is important to understand the role of the P2Y12 receptor in inflammation.     

Binding of Polysaccharide to Peptidoglycan in Cell Wall of Streptomyces roseochromogenes

The polysaccharide-peptidoglycan complex, which was prepared with lysozyme from Streptomyces roseochromogenes IAM53 cell walls, was hydrolyzed with lytic enzyme of Flavo-bacterium to separate polysaccharide. The enzymatically prepared polysaccharide (100 mg) contained 500 μmoles of hexoses, 40 μmoles of hexosamines and 31 μmoles of phosphate. Hexoses consisted of mannose and galactose in a molar ratio of 5 to 1. Hexosamines consisted of equimolar glucosamine and muramic acid, a half of which was identified as muramic acid 6-phosphate. The reducing end of the polysaccharide was muramic acid. The polysaccharide extracted with trichloroacetic acid contained no muramic acid-phosphate. So the polysaccharide moiety of S. roseochromogenes cell walls must be linked covalently to 6-position of muramic acid in peptidoglycan through phosphate,     

Elongation of teichuronic acid chains by a wall-membrane preparation from Micrococcus luteus.

A wall-plus-membrane preparation from Micrococcus luteus catalyzes the incorporation of [14C]glucose from UDP-[14C]glucose, into two fractions of teichuronic acid, which is the cell wall polysaccharide consisting of alternating residues of glucose and N-acetylmannosaminuronic acid (ManNAcUA). Membrane-associated teichuronic acid was extracted from the wall-membrane fraction of reaction mixtures by sodium dodecyl sulfate. The synthesis of membrane-associated teichuronic acid required UDP-glucose, UDP-ManNAcUA, and UDP-N-acetylglucosamine and was inhibited by tunicamycin. Glucose incorporated into wall-bound teichuronic acid remained in wall fragments after extraction with sodium dodecyl sulfate, and its incorporation required UDP-glucose and UDP-ManNAcUA (but not UDP-N-acetylglucosamine) and was insensitive to tunicamycin. Radioactive material incorporated into wall-bound teichuronic acid could be released by treatment with mild acid or by digestion with lysozyme, indicating that the wall-bound teichuronic acid was covalently linked to peptidoglycan. There were about 600 pmol of wall-bound teichuronic acid acceptor sites for glucose per mg of protein as measured in incorporation reaction mixtures lacking UDP-ManNAcUA. In the presence of both UDP-glucose and UDP-ManNAcUA, elongation of teichuronic acid acceptor sites occurred, with the addition of six to eight disaccharide units to each acceptor site.     

Component from the cell surface of the hydrocarbon-utilizing yeast Candida tropicalis with possible relation to hydrocarbon transport.

A polysaccharide-fatty acid complex was isolated from the cell surface of Candida tropicalis growing on alkanes. This complex was solubilized by Pronase treatment of whole cells. A decrease in alkane-binding affinity was observed after Pronase treatment, resulting in 10 to 12% of the yeast dry cell weight being released as polysaccharide. The isolated polysaccharide contained 2.5% fatty acids. C. tropicalis and Saccharomyces cerevisiae grown with glucose contained only traces of fatty acids in the corresponding polysaccharide fraction. The fatty acids were not removed from the polysaccharide moiety by gel filtration. Extraction of the polysaccharide with chloroform-methanol showed that fatty acids were covalently bound to the polysaccharide. The amphipathic nature of the isolated polysaccharide and the hydrocarbon-induced formation suggest a possible role in alkane metabolism.     

Cell wall constituents of Microcystis sp. PCC 7806

Cell walls of Microcystis sp. PCC 7806 were purified from cell homogenates by sucrose density centrifugation and Triton X-100 extraction. The outer membrane contained carotenoids, two major peptidoglycan-associated proteins (Mr 49,000 and 52,000), and lipopolysaccharide (LPS) as indicated by the presence of 3-hydroxy fatty acids (3-OH-14:0, 3-OH-16:0, 3-OH-18:0), 4-oxo-18:0 fatty acid, and GlcN as lipid A components in addition to rare O-methyl sugars (2-O-methyl-6-deoxyhexoses I and II). The peptidoglycan (A1 gamma-type) was found to be covalently linked to a wall polysaccharide composed of GlcN, ManN, Man, Glc, and phosphate.     

Structure of a Micrococcus lysodeikticus cell wall fragment containing phosphorylated sugars.

A polysaccharide-peptidoglycan complex containing different phosphorylated sugars from Micrococcus lysodeikticus cell wall has been isolated and purified. The peptidoglycan contained muramic acid 6-phosphate and N-acetylglucosamine 6-phosphate as phosphorylated sugars in addition to other sugar residues. Mild acid hydrolysis of the peptidoglycan and subsequent reduction of the released polysaccharide showed therein the presence of glucose and N-acetyl-glucosamine in the linkage of the external polysaccharide residues to the peptidoglycan through phosphodiester linkage. These data suggest the presence of polysaccharide chains linked to a peptidoglycan core through two phosphorylated sugars via two different terminal carbohydrate residues of the external polysaccharide chains in a same polymer.     

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).     

Cadaverine is covalently linked to peptidoglycan in Selenomonas ruminantium.

Cadaverine was found to exist as a component of cell wall peptidoglycan of Selenomonas ruminantium, a strictly anaerobic bacterium. [14C]cadaverine added to the growth medium was incorporated into the cells, and about 70% of the total radioactivity incorporated was found in the peptidoglycan fraction. When the [14C]cadaverine-labeled peptidoglycan preparation was acid hydrolyzed, all of the 14C counts were recovered as cadaverine. The [14C]cadaverine-labeled peptidoglycan preparation was digested with lysozyme into three small fragments which were radioactive and were positive in ninhydrin reaction. One major spot, a compound of the fragments, was composed of alanine, glutamic acid, diaminopimelic acid, cadaverine, muramic acid, and glucosamine. One of the two amino groups of cadaverine was covalently linked to the peptidoglycan, and the other was free. The chemical composition of the peptidoglycan preparation of this strain was determined to be as follows: L-alanine-D-alanine-D-glutamic acid-meso-diaminopimelic acid-cadaverine-muramic acid-glucosamine (1.0:1.0:1.0:1.0:1.1:0.9:1.0).     

Study of the composition of cell wall of group A Streptococcus after hydrolysis using muramidase from Streptomyces levoris

The aim of the experiment was to study the lysis products of cell walls of group A streptococci resulting from exposure to N-acetylmuramidase. It was shown that for isolating surface proteins free of polysaccharide and peptidoglycan fragments it was necessary to treat the streptococcal cell walls with endo-beta-N-acetylmuramidase for no more than 30 minutes. Prolonged hydrolysis with muramidase led to the presence of polysaccharide and the peptidoglycan fragments in the protein fractions, intracellular wall proteins covalently bound to the peptidoglycan fragments and polysaccharide being also released.     

Orinithine as a constituent of the peptidoglycan of Chloroflexus aurantiacus,diaminopimelic acid in that of Chlorobium vibrioforme f. thiosulfatophilum

L-Ornithine is the only diamino acid of the peptidoglycan of the gliding phototrophic Chloroflexus aurantiacus. The other constituents are L- and D-alanine, D-glutamic acid, N-acetyl-glucosamine and N-acetyl-muramic acid (in part as muramic acid-6-phosphate), all in approximate equimolar ratios to L-ornithine, aside from small amounts of glycine and histidine. Furthermore unlike typical Gram-negative bacteria, protein is not bound to this peptidoglycan. Instead, the rigid layer (sodium dodecyl sulfate insoluble cell wall fraction) contained large amounts of a complex polysaccharide consisting of sugar O-methyl ethers, hexoses and pentoses. Its binding site is presumably muramic acid-6-phosphate of the peptidoglycan.In contrast, in Chlorobium vibrioforme f. thiosulfatophilium, meso-diaminopimelic acid was found as the only diamino acid of this peptidoglycan. As with other Gramnegative bacteria, L- and D-alanine, D-glutamic acid, N-acetyl-glucosamine and N-acetyl-muramic acid (no muramic acid-6-phosphate) were observed in approximate equimolar ratios to meso-diaminopimelic acid, except a lower D-alanine content. The rigid layer of Chlorobium vibrioforme f. thiosulfatophilum contained protein, and there were no indications for a complex polysaccharide comparable to that of Chloroflexus aurantiacus.Abbreviations Ala alanine - A₂pm diaminopimelic acid - GC/MS combined gas-liquid chromatography/mass spectrometry - GlcNAc N-acetyl-glucosamine - Glu glutamic acid - Gly glycine - HF hydrofluoric acid - Lys lysine - MurNAc N-acetyl-muramic acid - Orn ornithine - SDS sodium dodecyl sulfate     

Polysaccharides of crithidia fasciculata. Identification and partial characterization of a cell surface constituent.

A carbohydrate-containing fraction was extracted from the trypanosomatid Crithidia fasciculata by a phenol-water procedure. Ion-exchange chromatography separated this fraction into three components: a polysaccharide which was not retained on the column; RNA which eluted upon addition of salt; and, another polysaccharide which eluted upon addition of detergent. The unretained fraction was shown to be composed solely of D-mannose. The mannan, which was heterodisperse on Sephadex G-100, had an average molecular weight of approx. 14 000 as based on analysis of reducing groups. The detergent-eluted material yielded arabinose and galactose upon acid hydrolysis. The arabinogalactan was excluded from Sephadex G-100 and Sephacryl S-200 molecular sieve columns, suggesting a molecular weight greater than or equal to 200 000. Cell fractionation studies showed the bulk of extractable polysaccharide was associated with a particulate fraction. Further determination of the cellular localization of the polysaccharide was accomplished by employing a specific antiserum prepared from rabbits immunized with the polysaccharide extract. The cell surface localization of the arabinogalactan was demonstrated by cell agglutination studies as well as immunocytochemical techniques using fluorescein and ferritin conjugated antibodies.     

Isolation of a coaggregation-inhibiting cell wall polysaccharide from Streptococcus sanguis H1.

Coaggregation between Streptococcus sanguis H1 and Capnocytophaga ochracea ATCC 33596 cells is mediated by a carbohydrate receptor on the former and an adhesin on the latter. Two methods were used to release the carbohydrate receptor from the gram-positive streptococcus, autoclaving and mutanolysin treatment. The polysaccharide released from the streptococcal cell wall by either treatment was purified by ion-exchange chromatography; this polysaccharide inhibited coaggregation when preincubated with the gram-negative capnocytophaga partner. After hydrolysis of the polysaccharide by hydrofluoric acid (HF), the major oligosaccharide of the polysaccharide was purified by high-performance liquid chromatography. By analysis of the HF hydrolysis of the polysaccharide and the purified oligosaccharide, this major oligosaccharide appeared to be the repeating unit of the polysaccharide, with minor components resulting from internal hydrolysis of the major oligosaccharide. Gas chromatography results showed that the oligomer was a hexasaccharide, consisting of rhamnose, galactose, and glucose, in the ratio of 2:3:1, respectively. By weight, the purified hexasaccharide was a fourfold-more-potent inhibitor of coaggregation than the native polysaccharide. Resistance to hydrolysis by sulfuric acid alone and susceptibility to hydrolysis by HF suggested that oligosaccharide chains of the polysaccharide are linked by phosphodiester bonds. Studies with a coaggregation-defective mutant of S. sanguis H1 revealed that the cell walls of the mutant contained neither the polysaccharide nor the hexasaccharide repeating unit. The purification of both a polysaccharide and its constituent hexasaccharide repeating unit, which both inhibited coaggregation, and the absence of this polysaccharide or hexasaccharide on a coaggregation-defective mutant strongly suggest that the hexasaccharide derived from the polysaccharide functions as the receptor for the adhesin from C. ochracea ATCC 33596.     

Sphere-Rod Morphogenesis in Arthrobacter crystallopoietes I. Cell Wall Composition and Polysaccharides of the Peptidoglycan

Cell walls of Arthrobacter crystallopoietes were prepared from cells grown as spheres and from peptone- and succinate-induced rod stage cells. Undegraded polysaccharide backbones of the peptidoglycans were isolated from myxobacter AL-1 protease digests by ECTEOLA cellulose and Sephadex G-50 chromatography. The polysaccharide backbones of the sphere cell wall peptidoglycan are heterogeneous in their size, and average less than 40 hexosamines per chain. Those of the rod cell walls are homogeneous in size and average 114 to 135 hexosamines per chain.     

Primary structure of the peptidoglycan from the unicellular cyanobacterium Synechocystis sp. strain PCC 6714

A peptidoglycan fraction free of non-peptidoglycan components was isolated from the unicellular cyanobacterium Synechocystis sp. strain PCC 6714. Hydrofluoric acid treatment (48%, 0 degrees C, 48 h) cleaved off from the peptidoglycan non-peptidoglycan glucosamine, mannosamine, and mannose. The purified peptidoglycan consists of N-acetyl muramic acid, N-acetyl glucosamine, L-alanine, D-alanine, D-glutamic acid, and meso-diaminopimelic acid in approximately equimolar amounts. At least partial amidation of carboxy groups in the peptide subunits is indicated. Peptide analyses and 2,4-dinitrophenyl studies of partial acid hydrolysates revealed the structure of the Synechocystis sp. strain PCC 6714 peptidoglycan to belong to the A1 gamma type (direct cross-linkage) of peptidoglycan classification. The degree of cross-linkage is about 56% and thus is in the range of that found in gram-positive bacteria. Some of the peptide units are present as tripeptides lacking the carboxy-terminal D-alanine.     

Capsule polysaccharide-protein-peptidoglycan complex in the cell envelope of Rhodobacter capsulatus

The capsule polysaccharide-protein-peptidoglycan complex (insoluble in boiling sodium dodecyl sulfate and hot phenol-water) from cell envelopes of Rhodobacter capsulatus St. Louis was characterized. Hydrofluoric, hydrochloric acid or alkaline hydrolysis solubilized the polysaccharide moiety, whereas the protein-peptidoglycan moiety remained insoluble. On treatment of the protein-peptidoglycan moiety with lysozyme, the protein with peptidoglycan-residues bound was solubilized. It showed a single, broad peptide band (M _r=about 17,000) on sodium dodecyl sulfate polyacrylamide gel-electrophoresis. The same protein was obtained by lysozyme digestion (without preceding hydrofluoric or hydrochloric acid treatment) of the protein-peptidoglycan complex of the phage-resistant mutant Rhodobacter capsulatus St. Louis RC1^-, in which the capsule polysaccharide is present in a free form. A protein-peptidoglycan complex was isolated also from the capsulefree Rhodobacter capsulatus 37b4. Covalent binding between the protein and peptidoglycan moieties is likely for all three strains as is the lipoprotein nature of the protein moiety. The polysaccharide moiety of the complete complex from the wild-type Rhodobacter capsulatus St. Louis was at least partly removable from the complex in the presence of high salt concentrations or ethylene diamine tetraacetate. A specific amino acid pattern (with Ser, Gly, Glu, and Ala dominating) remained constantly associated with the capsule polysaccharide moiety independent of the separation procedure.Abbreviations A₂pm diaminopimelic acid - Cetavlon cetyltrimethyl-ammonium bromide - EDTA ethylene-diaminetetraacetate, disodium salt - HF hydrofluoric acid - HPLC high-performance liquid chromatography - PAGL polyacrylamide gel-electrophoresis - SDS sodium dodecyl sulfate - TCA trichloroacetic acid     

Antigenic polysaccharides of bacteria of the genus Shigella. Determination of the structure of polysaccharide chains of Shigella boydii type 9 lipopolysaccharide and detection of unusually high molecular weight glycolipid

Specific acidic polysaccharide has been isolated from the Shigella boydii type 9 antigenic lipopolysaccharide after mild hydrolysis followed by chromatography on Sephadex G-50. The polysaccharide consists of D-glucose, D-glucuronic acid, 2-acetamido-2-deoxy-D-glucose, and L-rhamnose. From the results of methylation analysis, partial acid hydrolysis and 13C NMR data the structure of the repeating unit of the polysaccharide was deduced as follows: [----4)DGlcp(alpha 1----4)DGlcAp(beta 1----3)DGlcNAcp(alpha 1----3)LRhap(alpha 1----]n. The lipopolysaccharide from Sh. boydii 9 was fractionated by gel chromatography on the Sephadex G-200 column in a buffer containing sodium deoxycholate into three fractions. PAGE-SDS of the fractions obtained, 13C NMR- and chromato-mass-spectrometry data indicated that the three fractions contained the O-specific polysaccharide as the only carbohydrate component. The substance from the most high-molecular weight fraction contained unusually long O-specific chains (60,000 dalton). In the fat acid composition this fraction differed from other lipopolysaccharides by absence of beta-hydroxymyristic acid.     

Covalent linkage of the type- and group-specific antigens to the peptide moiety of the peptidoglycan of serotype III group BStreptococcus

The attachment sites for the two major cell wall polysaccharides, the type-and group-specific antigens of a serotype III group B streptococcus (GBS) were investigated with [14C]lysine to label the peptide portion of the peptidoglycan and [3H]acetate to label both polysaccharide antigens as well as the glycan backbone of the peptidoglycan. Mutanolysin-treated cell walls were subjected to trypsin digestion, followed by exhaustive beta-elimination with 6N ammonium hydroxide at 37°C. The resulting products were purified by column chromatography prior to chemical, immunological, and high-voltage electrophoresis analyses. Data from these studies indicated that both cell wall polymers are covalently attached to the peptidoglycan via the peptide unit. Additionally, during synthesis and assembly both antigens attached only to nascent peptidoglycan.     

Cadaverine covalently linked to a peptidoglycan is an essential constituent of the peptidoglycan necessary for the normal growth in Selenomonas ruminantium

Cadaverine links covalently to the D-glutamic acid residue of the peptidoglycan in Selenomonas ruminantium, a strictly anaerobic Gram-negative bacterium (Kamio, Y., Itoh, Y., and Terawaki, Y. (1981) J. Bacteriol. 146, 49-53). This report clarifies a physiological function of cadaverine in this organism by using DL-alpha-difluoromethyllysine, which had previously been shown to be a selective irreversible inhibitor of lysine decarboxylase of Mycoplasma dispar (P?s?, H., MaCann, P.P., Tanskanen, R., Bey, P., and Sjoerdsma, A. (1984) Biochem. Biophys. Res. Commun. 125, 205-210). DL-alpha-Difluoromethyllysine is now shown to be a potent and irreversible inhibitor of lysine decarboxylase of S. ruminantium in vitro; however, it did not inhibit the transfer of cadaverine to the alpha-carboxyl group of the D-glutamic acid residue of the peptidoglycan. DL-alpha-Difluoromethyllysine at 5 mM markedly inhibited the growth of the bacterium and caused rapid cell lysis. Immediately before the cell lysis, almost all cells became swollen, and such cells showed a loosened envelope structure when studied by electron microscopy. The peptidoglycan prepared from the DL-alpha-difluoromethyllysine-treated cells did not have covalently linked cadaverine. The growth inhibition by DL-alpha-difluoromethyllysine was completely reversed by adding cadaverine (1 mM) to the medium. Furthermore, the exogenous cadaverine was exclusively incorporated into the peptidoglycan in the presence of DL-alpha-difluoromethyllysine (5 mM), and a normal peptidoglycan was synthesized. The cell lysis and the formation of an abnormal cell structure were completely prevented by cadaverine added to the medium. We conclude that cadaverine covalently linked to the peptidoglycan in S. ruminantium is an essential constituent of the peptidoglycan and is required for cell surface integrity and the normal growth of S. ruminantium.