Teichoic and teichuronic acids: biosynthesis, assembly, and location

Bacterial antigen immunolabeling in macrophages after phagocytosis and degradation of Bacillus subtilis

After phagocytosis of Bacillus subtilis 168 by bone marrow-derived macrophages, the intracellular pathway followed by different antigens was studied by immunofluorescence and immunoelectron microscopy. Three different rabbit antisera were used: (i) an antiserum to B. subtilis whole cells mainly recognizing the cell wall constituents, (ii) an antiserum to teichoic acid, and (iii) an antiserum to peptidoglycan recognizing the disaccharide tetrapeptide molecules resulting from peptidoglycan degradation. During the first 3 h after phagocytosis of B. subtilis, the three antisera were confined to the same vacuolar compartments, as follows. They were first found in phagosomes gathered in the perinuclear region. Upon bacterial degradation, the three antisera colocalized in an increasing number of small dense vesicles, located in the perinuclear region, that seemed to result from the fragmentation of phagolysosomes. These vesicles correspond to an acidic compartment since they also stained for 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine, a drug known to accumulate in the acidic compartments of cells. At later time points, the antigens recognized by the three antisera followed different pathways. After 18 h, teichoic acid and peptidoglycan were no longer detectable in macrophages whereas an antigen(s) labeled with antiserum to B. subtilis whole cells remained stocked for several days in small acidic vesicles randomly distributed throughout the macrophage. This compartment appeared to be different from the one labeled during the first 3 h after ingestion of bacteria. These results suggest that the transport rate and the compartments implicated in antigen processing differ according to the antigen.

Expression of heterologous genes for wall teichoic acid in Bacillus subtilis 168

A localized region of low DNA sequence homology was revealed in two strains of Bacillus subtilis by a specific 100-fold reduction in transformation by W23 DNA of the tag1 locus, a teichoic acid marker of strain 168. Fifty nine rare recombinants, hybrid at this locus, had all acquired donor-specific phage resistance characters, while losing those specific to the 168 recipient. Chemical analysis of isolated cell walls showed that these modifications are associated with major changes in the wall teichoic acids. Genetic analysis demonstrated that determinants for the ribitol phosphate polymer of strain W23 had been transferred to 168, replacing those for the glycerol phosphate polymer in the recipient. All W23 genes coding for poly(ribitol phosphate) in the hybrids and those specifying anionic wall polymers in strain 168 are clustered near hisA. In addition to tag1, the region exchanged extends just beyond gtaA in some hybrids, whereas in others it may include the more distant gtaB marker, encompassing a region sufficient to contain at least 20 average-sized genes. Surface growth, flagellation, transformability and sporulation all appeared normal in hybrids examined. Recombinants without a major wall teichoic acid from either strain were not found, suggesting that an integral transfer of genes for poly(ribitol phosphate) from W23 had occurred in all hybrids isolated. We interpret these results as indicating an essential role for anionic wall polymers in the growth of B. subtilis.

Lipoteichoic acid from Bacillus subtilis subsp. niger WM: isolation and effects on cell wall autolysis and turnover

Lipoteichoic acid (LTA) was extracted by means of hot aqueous phenol from Bacillus subtilis subsp. niger WM cells grown under various conditions in chemostat culture. The extracts were partially purified by nuclease treatment and gel permeation chromatography. Chemical analyses revealed a composition consistent with a polyglycerol phosphate polymer. The influence on autolysis of the LTAs thus obtained was studied with both whole cells and autolysin-containing native walls of B. subtilis subsp. niger WM. Lysis rates of phosphate-limited cells could be reduced to about 40% of the control rate by the addition of LTA, whereas lysis of cells grown under phosphate-sufficient conditions was affected to a much lesser extent. The lysis of native walls prepared from variously grown cells proved to be fairly insensitive to the addition of LTA. The effect of LTA on wall turnover was studied by following the release of radioactively labeled wall material during exponential growth. The most obvious effect of LTA was a lowered first-order rate of release of labeled wall material; calculations according to the model for cell wall turnover in Bacillus spp. formulated by De Boer et al. (W. R. De Boer, F. J. Kruyssen, and J. T. M. Wouters, J. Bacteriol. 145:50-60, 1981) revealed changes in wall geometry and not in turnover rate in the presence of LTA.

In vitro studies simultaneously examining effect of oxacillin on uptake of radiolabeled streptomycin and on associated bacterial lethality in Staphylococcus aureus

We studied the effects of various concentrations of oxacillin on streptomycin uptake and killing for several strains of Staphylococcus aureus. When streptomycin was present in concentrations below the MIC, addition of oxacillin at concentrations greater than or equal to the MIC was associated with both significantly increased aminoglycoside uptake and killing. In contrast, when streptomycin was present in concentrations above the MIC, no increase of streptomycin uptake was noted with the addition of oxacillin, and killing was no greater than what would have been expected with a simply additive effect. Similar studies in a strain of S. aureus selected for high-level streptomycin resistance also demonstrated increased streptomycin uptake in the presence of concentrations of oxacillin above the MIC; however, killing was no greater than that seen with oxacillin alone. These studies provide data which are potentially important in designing a rational approach to clinical use of combination antibiotic therapy.

Biosynthesis of a galactose-and galacturonic acid-containing polysaccharide in Rhizobium meliloti

Previous work showed that two different strains derived from a culture of Rhizobium meliloti 102F51 differed with respect to phage specificity, agglutinability by alfalfa seed lectin, and synthesis of a galactose-containing polysaccharide (R. A. Ugalde, H. Handelsman, and W. J. Brill, J. Bacteriol. 166:148-154, 1986). Inner membranes from the more competitive strain incorporated galactose from UDP-galactose when a thermostable factor was present. This factor has now been identified as UDP-galacturonic acid. UDP-glucuronic acid was also active as a donor; however, this activity may be due to the presence of a 4-epimerase. Galacturonic acid, together with galactose, is incorporated into the reaction product, which appears to be a polysaccharide formed by several repeating units of these two monosaccharides. Partial acid hydrolysis liberates the disaccharide with galactose at the reducing end.

Action of lombazole, and inhibitor of fungal ergosterol biosynthesis, on Staphylococcus epidermidis

Lombazole had no effect on respiration at any tested concentration and had little effect on the K+ permeability of Staphylococcus epidermidis. Of the major metabolic processes investigated in this bacterium, only de novo synthesis of the cell envelope was inhibited by lombazole well in advance of an effect on growth. The time course of inhibition indicated that lombazole exerted its primary effect via inhibition of lipid synthesis; other induced changes, such as reduced synthesis of lipoteichoic acid and cell wall components, were considered to be secondary effects. Although the precise site of action in S. epidermidis has to be established, the absence of alterations in lipid patterns after treatment with lombazole suggests the toxicant may affect an essential step in lipid biosynthesis. In Candida albicans, lombazole inhibited the sterol C-14 demethylation step in the ergosterol biosynthesis pathway.

Phosphatidylglycerol as biosynthetic precursor for the poly(glycerol phosphate) backbone of bifidobacterial lipoteichoic acid

Phosphatidylglycerol functions as donor of the sn-glycerol 1-phosphate units in the synthesis in vitro of the 1,2-phosphodiester-linked glycerol phosphate backbone of the lipoteichoic acids of Bifidobacterium bifidum subsp. pennsylvanicum. The incorporation was catalysed by a membrane-bound enzyme system. After addition of chloroform/methanol the product formed coprecipitated with protein. The material was phenol-extractable and was co-eluted with purified lipoteichoic acid on Sepharose 6B. The reaction was stimulated by Triton X-100, UDP-glucose and UDP-galactose, but Mg2+ ions had no effect. The apparent values for Km and Vmax. of the phosphatidylglycerol incorporation were 1.4 mM and 3.1 nmol/h per mg of membrane protein, respectively. Labelled UDP-glucose and UDP-galactose were not incorporated into the lipoteichoic acid fraction by the particulate membrane preparation.

Pneumococcal Forssman antigen: enrichment in mesosomal membranes and specific binding to the autolytic enzyme of Streptococcus pneumoniae

The choline-containing pneumococcal membrane teichoic acid (Forssman antigen) can be isolated with the membrane fractions of the bacteria. The small vesicle (mesosomal) fraction generated during the formation of protoplasts seems to be highly enriched in this material. Forssman antigen was identified in cell fractions on the basis of (i) radioactive choline label, (ii) autolysin-inhibitory activity, and (iii) the sedimentation profile in sucrose density gradients with and without detergent. A membrane teichoic acid could also be isolated from pneumococci grown in medium in which choline was replaced by ethanolamine as the nutritionally required amino alcohol. This material contained radioactive ethanolamine label and behaved similarly to the choline-containing membrane teichoic acid during centrifugation in detergent-containing and detergent-free density gradients. On the other hand, the material had only low autolysin-inhibitory activity. Binding of pure pneumococcal autolysin to micelles of purified Forssman antigen could be demonstrated by mixing these components in vitro and analyzing them by sucrose density gradients and by agarose chromatography. No binding could be observed between the pneumococcal enzyme and the micellar forms of either cardiolipin or polyglycerophosphate-type lipoteichoic acid isolated from Streptococcus lactis.

Purification and characterization of Staphylococcus aureus type 8 capsular polysaccharide

Clinical isolates of Staphylococcus aureus have been previously classified into eight types on the basis of their capsular polysaccharide. The high prevalence of the type 8 capsular polysaccharide among bacteremic isolates suggests the importance of this capsular antigen in staphylococcal disease. The capsular polysaccharide was purified from extracts of three clinical isolates of S. aureus type 8 of different geographic and temperal origin by ion-exchange chromatography and gel filtration. Gas chromatography, gas chromatography-mass spectrometry, and 13C-nuclear magnetic resonance showed that the type 8 capsular polysaccharide is composed of O-acetyl groups, N-acetylfucosamine, and an aminouronic acid similar to N-acetylgalactosaminouronic acid. The purified polysaccharide reacted only with type 8 antiserum in double diffusion experiments. Our analysis shows that the type 8 polysaccharide is both chemically and serologically distinct from teichoic acid and previously characterized polysaccharides of S. aureus.

A new type of carbohydrate-containing synthetic antigen: synthesis of carbohydrate-containing polyacrylamide copolymers having the specificity of O:3 and O:4 factors of Salmonella

The synthesis of a new type of synthetic antigen that contains no protein is described. Two linear polyacrylamide copolymers with carbohydrate branches were obtained via radical copolymerisation of the allyl glycosides of the oligosaccharide determinants O-beta-D-mannopyranosyl-(1----4)-O-alpha-L-rhamnopyranosyl-(1----3 )-beta-D- galactopyranose and O-3,6-dideoxy-alpha-D-xylo-hexopyranosyl-(1----3)-alpha-D-mannopyranose with acrylamide. These copolymers, which contained 30% of carbohydrate and had molecular masses exceeding 100 kilodaltons, had the group specificity E and B of Salmonella.

Specific immunoglobulin A antibodies to a peptide subunit sequence of bacterial cell wall peptidoglycan

Immunoglobulin A (IgA) antibodies in human sera with binding specificity for the C-terminal R-D-Ala-D-Ala sequence of the precursor peptide from bacterial cell wall peptidoglycan were detected by an enzyme-linked immunosorbent assay (ELISA). Specificity of the test system was proved by comparing the high binding of specific IgA to albumin-(D-Ala3) as an antigen with the failure to bind to albumin-(L-Ala3), by binding inhibition studies with L-Ala3, D-Ala3, or peptides with structural analogy to peptidoglycan peptide subunit peptides as inhibitors, and by excluding binding of peroxidase-labeled anti-human IgA to immunoglobulin classes others than IgA. Interference of rheumatoid factors of IgA class was excluded by an ELISA for assaying IgA-rheumatoid factor and by the fact that an IgA fraction essentially free of IgG and IgM was isolated from a serum reacting strongly positive in the ELISA for measuring specific IgA to the peptide subunit of peptidoglycan. This isolated IgA again exhibited binding specificity in the ELISA, thus corroborating the existence of specific IgA in human serum to the C-terminal R-D-Ala-D-Ala sequence of peptidoglycan precursor peptide. The existence of IgA antibodies with specificity for bacterial peptidoglycan was further proved by preadsorption of serum to peptidoglycans and subsequent measurement of specific IgA in the ELISA. Screening of human sera for IgA antibodies with specificity for R-D-Ala-D-Ala peptides revealed that specific antibodies directed against this sequence of bacterial cell wall peptidoglycan may be detected in several human sera.

Role of cellular lipoteichoic acids in mediating adherence of serotype III strains of group B streptococci to human embryonic, fetal, and adult epithelial cells

Lipoteichoic acids (LTA) of serotype III strains of group B streptococci (GBS) were shown to mediate adherence of these organisms to human embryonic (HEC), fetal (HFC), and adult buccal (HBEC) epithelial cells. The binding of GBS was temperature dependent, and maximum attachment occurred at 37 degrees C. HEC, HFC, and HBEC preincubated with purified LTA significantly inhibited attachment of GBS, whereas the group B and type III antigens had no effect. Under phosphate-limiting conditions in which cell-associated LTA could not be detected in these organisms, bacterial adherence did not take place. GBS (virulent) that were isolated from infected infants and previously shown to have significantly higher quantities of cell-associated LTA in comparison to GBS strains from asymptomatically colonized infants adhered with greater binding avidity to HEC and HFC and in greater numbers than to HBEC. It was determined that the mechanism of LTA-mediated adherence of GBS to HBEC differed from adherence to embryonic and fetal cells for both virulent and asymptomatic GBS strains bound to HBEC in a similar manner, enhanced by the lipid portion of the LTA. In contrast, the binding of GBS to HEC and HFC was mediated by hydrophobic as well as specific interactions due to the glycerolphosphate polymer of LTA. These results indicate that possible receptor sites for LTA present on cells in prenatal stages of development may differ from those of adult cells, which may result in increased susceptibility of newborn infants to group B streptococcal disease. The implications of LTA-mediated adherence of GBS and their possible role as virulence factors are discussed.

Production and release of peptidoglycan and wall teichoic acid polymers in pneumococci treated with beta-lactam antibiotics

Autolysin-defective pneumococci treated with inhibitory concentrations of penicillin and other beta-lactam antibiotics continued to produce non-cross-linked peptidoglycan and cell wall teichoic acid polymers, the majority of which were released into the surrounding medium. The released cell wall polymers were those synthesized by the pneumococci after the addition of the antibiotics. The peptidoglycan and wall teichoic acid chains released were not linked to one another; they could be separated by affinity chromatography on an agarose-linked phosphorylcholine-specific myeloma protein column. Omission of choline, a nutritional requirement and component of the pneumococcal teichoic acid, from the medium inhibited both teichoic acid and peptidoglycan synthesis and release. These observations are discussed in terms of plausible mechanisms for the coordination between the biosynthesis of peptidoglycan and cell wall teichoic acids.

Location of Peptidases Outside and Inside the Membrane of Streptococcus cremoris

Peptidase activity determinations involving native cells of Streptococcus cremoris and completely disrupted cell preparations, as well as experiments concerned with peptidase activity distribution among cell fractions obtained by a damage-restrictive removal of the cell wall and release of intracellular material, suggest the presence of peptidases with distinguishable locations. Alanyl, leucyl, and prolyl aminopeptidase activities are most likely located in the cell wall-membrane interface, showing no detectable association with the membrane. Lysyl aminopeptidase is present not only in this location, but also as an intracellular enzyme. Endopeptidase activity and glutamate aminopeptidase activity appear to be weakly associated with the membrane. The locations of these two peptidase activities, unlike those of the former aminopeptidase activities, impose a restriction on their expression. Results of experiments concerned with permeabilization of the membrane and findings regarding an effect of the local environment of the enzymes on their pH activity profiles are evaluated and considered as being indicative of the proposed location. The possible implications of these findings with respect to protein utilization during growth of the organism in milk are discussed.

Peptidoglycan synthesis by partly autolyzed cells of Bacillus subtilis W23

Partly autolyzed, osmotically stabilized cells of Bacillus subtilis W23 synthesized peptidoglycan from the exogenously supplied nucleotide precursors UDP-N-acetylglucosamine and UDP-N-acetylmuramyl pentapeptide. Freshly harvested cells did not synthesize peptidoglycan. The peptidoglycan formed was entirely hydrolyzed by N-acetylmuramoylhydrolase, and its synthesis was inhibited by the antibiotics bacitracin, vancomycin, and tunicamycin. Peptidoglycan formation was optimal at 37 degrees C and pH 8.5, and the specific activity of 7.0 nmol of N-acetylglucosamine incorporated per mg of membrane protein per h at pH 7.5 was probably decreased by the action of endogenous wall autolysins. No cross-linked peptidoglycan was formed. In addition, a lysozyme-resistant polymer was also formed from UDP-N-acetylglucosamine alone. Peptidoglycan synthesis was inhibited by trypsin and p-chloromercuribenzenesulfonic acid, and we conclude that it occurred at the outer surface of the membrane. Although phospho-N-acetylmuramyl pentapeptide translocase activity was detected on the outside surface of the membrane, no transphosphorylation mechanism was observed for the translocation of UDP-N-acetylglucosamine. Peptidoglycan was similarly formed with partly autolyzed preparations of B. subtilis NCIB 3610, B. subtilis 168, B. megaterium KM, and B. licheniformis ATCC 9945. Intact protoplasts of B. subtilis W23 did not synthesize peptidoglycan from externally supplied nucleotides although the lipid intermediate was formed which was inhibited by tunicamycin and bacitracin. It was therefore considered that the lipid cycle had been completed, and the absence of peptidoglycan synthesis was believed to be due to the presence of lysozyme adhering to the protoplast membrane. The significance of these results and similar observations for teichoic acid synthesis (Bertram et al., J. Bacteriol. 148:406-412, 1981) is discussed in relation to the translocation of bacterial cell wall polymers.

Biosynthesis of D-alanyl-lipoteichoic acid: role of diglyceride kinase in the synthesis of phosphatidylglycerol for chain elongation

Lipophilic and hydrophilic D-alanyl-lipoteichoic acids are elongated in Lactobacillus casei by the transfer of sn-glycerol 1-phosphate units from phosphatidylglycerol to the poly(glycerophosphate) moiety of the polymer. These sn-glycerol 1-phosphate units are added to the end of the poly(glycerophosphate) which is distal to the glycolipid anchor; 1,2-diglyceride results from this addition. The presence of a diglyceride kinase was suggested by the ATP-dependent phosphorylation of 1,2-diglyceride to phosphatidic acid. Inorganic phosphate was used to initiate the synthesis of lipophilic lipoteichoic acid (LTA) and the elongation of both lipophilic and hydrophilic LTA. Three observations suggest that phosphate and other anions play a role in the in vitro synthesis of LTA and its precursors. First, the conversion of 1,2-diglyceride to phosphatidic acid by diglyceride kinase was stimulated. Second, the synthesis of phosphatidylglycerol was increased. Third, the elongation of lipophilic and hydrophilic LTA was enhanced. These observations indicated that one effect of phosphate might be to enhance the utilization of 1,2-diglyceride for the synthesis of phosphatidic acid. This phospholipid is a precursor of phosphatidylglycerol, the donor of sn-glycerol 1-phosphate for elongation of LTA.

Association of elevated levels of cellular lipoteichoic acids of group B streptococci with human neonatal disease

Cell-associated lipoteichoic acids (LTAs) from late-exponential-phase cultures (serotypes Ia, Ib, Ic, II, and III) of group B streptococci isolated from infected and asymptomatically colonized infants were quantitated and characterized by growing the organisms in a chemically defined medium containing [3H]glycerol and [14C]acetate. Cell pellets were extracted with 45% aqueous phenol and chloroform-methanol and subjected to DEAE-Sephacel anion-exchange chromatography. Elution profiles resolved three major peaks, I, II, and III, with glycerol and phosphate present in a 1:1 molar ratio in each peak, and results obtained by Ouchterlony immunodiffusion analysis confirmed the presence of poly(glycerol phosphate). Saponification indicated that [14C]acetate was incorporated into fatty acids of peaks I and II only, suggesting that these were cell-associated LTAs. Peak II was of small molecular weight (less than 10,000) and probably represented another species of LTA. Peaks I and II were further demonstrated to be LTA by their ability to sensitize human type O erythrocytes. Peak III lacked fatty acids and was shown to probably be deacylated LTA. Quantitation of cell-associated teichoic acid material produced by the group B streptococcal strains indicated that the clinical isolates from infants with early- or late-onset disease possessed significantly higher levels than did the asymptomatic (clinical isolates from infants without symptoms of disease) group B streptococcal strains.

Levels of cell wall enzymes in endospores and vegetative cells of Bacillus subtilis

Vegetative bacilli and refractile endospores of Bacillus subtilis 168 were disrupted by homogenization with glass beads and fractionated by differential centrifugation. Most of the protein of endospores was particulate, whereas for bacilli most was soluble. Alanine racemase activity was sixfold higher in extract of endospores than in extract of bacilli and was particulate, whereas the enzyme from bacilli was soluble. The specific activities of seven other enzymes involved in peptidoglycan and teichoic acid biosynthesis were higher in extracts of bacilli than in those of endospores. The results suggest that restoration of activities of these seven enzymes to vegetative levels occurs during germination and outgrowth.

Teichoic acids from chemostat-grown cultures of Streptococcus mutans and Lactobacillus plantarum

We examined the effect of growth conditions in chemostat culture on the quantity and composition of the cell wall teichoic acids of Streptococcus mutans BHT and Lactobacillus plantarum NCIB 7220 and the membrane lipoteichoic acid from S. mutans Ingbritt. With the cell wall teichoic acids, which are covalently linked to peptidoglycan, the amount of teichoic acid is independent of the growth conditions employed. However, the extent of glucosyl substitution of the polymer from L. plantarum was dependent on growth conditions. S. mutans Ingbritt lipoteichoic acid, on the other hand, was little affected by growth conditions in terms of composition or serological activity, but the amount produced was markedly affected by changes in growth conditions.

Isolation and analysis of sacculi from Streptococcus sanguis

Sacculi were prepared from Streptococcus sanguis 34 by exhaustive extraction of bacteria with hot 1% sodium dodecyl sulfate-0.5% 2-mercaptoethanol. Lyophilized residue was dissociated by brief sonication to single bodies closely resembling streptococci in phase-contrast microscopic density, staining properties, and morphology. Electron micrographs revealed bodies that contained variable amounts of cellular contents and were bounded by intact cell walls. Chemical analyses of sacculi demonstrated the presence of peptidoglycan, carbohydrate, protein, and phosphate. The hexose content of sacculi varied 10-fold depending upon the composition of the growth medium. When sacculi were subjected to treatment with 5 M LiCl, 8 M urea, 40% phenol (25 degrees C), or dimethyl sulfoxide most of the nitrogen and carbohydrate present was recovered in the insoluble fraction. These data suggest that sacculi contain the cell wall fraction of the extracted bacteria and that most of the carbohydrates and proteins of sacculi are firmly bound to the insoluble fraction, which contains the peptidoglycan matrix.

Influence of phosphate supply on teichoic acid and teichuronic acid content of Bacillus subtilis cell walls

Bacillus subtilis 168 was grown in chemostat culture in fully defined media containing a constant concentration of magnesium and concentrations of phosphate that varied from those giving phosphate-limited growth to those in which phosphate was present in excess and magnesium was limiting. Phosphate-limited bacteria were deficient in wall teichoic acid and contained less than half as much cellular phosphate as did bacteria grown in excess of phosphate. Approximately 70% of the additional phosphate in the latter bacteria was present as wall teichoic acid, indicating that the ability of the bacteria to discontinue teichoic acid synthesis when grown under phosphate limitation permits a substantial increase in their growth yield. Since not all of the additional phosphate is present as wall teichoic acid other cellular phosphates may also be present in reduced amounts in the phosphate-limited bacteria. The content of phosphate groups in walls of magnesium-limited bacteria was similar to the content of uronic acid groups in walls of phosphate-limited bacteria, and walls of bacteria grown in media of intermediate composition contained intermediate proportions of the two anionic polymers. Phage SP50, used as a marker for the presence of teichoic acid, bound densely to nearly all of the bacteria in samples containing down to 22% of the maximum content of teichoic acid. Apparently, therefore, nearly all of these bacteria contain teichoic acid, and the population does not consist of a mixture of individuals having exclusively one kind of anionic polymer. Bacteria containing less than 22% of the maximum content of teichoic bound in a nonuniform manner, and possible explanations for this are discussed.

Major sites of metal binding in Bacillus licheniformis walls

Isolated and purified walls of Bacillus licheniformis NCTC 6346 his contained peptidoglycan, teichoic acid, and teichuronic acid (0.36 mumol of diaminopimelic acid, 0.85 mumol of organic phosphorus, and 0.43 mumol of glucuronic acid per mg [dry weight] of walls, respectively). The walls also contained a total of 0.208 mumol of metal per mg. When these walls were subjected to metal-binding conditions (T. J. Beveridge and R. G. E. Murray, J. Bacteriol. 127:1502-1518, 1976) for nine metals, the amount of bound metal above background ranged from 0.910 mumol of Na to 0.031 mumol of Au per mg of walls. Most were in the 0.500-mumol mg-1 range. Electron-scattering profiles from unstained thin sections indicated that the metal was dispersed throughout the wall fabric. Mild alkali treatment extracted teichoic acid from the walls (97% based on phosphorus) but left the peptidoglycan and teichuronic acid intact. This treatment reduced their capacity for all metals but Au. Thin sections revealed that the wall thickness had been reduced by one-third, but metal was still dispersed throughout the wall fabric. Trichloroacetic acid treatment of the teichoic acid-less walls removed 95% of the teichuronic acid (based on glucuronic acid) but left the peptidoglycan intact (based on sedimentable diaminopimelic acid). The thickness of these walls was not further reduced, but little binding capacity remained (usually less than 10% of the original binding). The staining of these walls with Au produced a 14.4-nm repeat frequency within the peptidoglycan fabric. Sedimentation velocity experiments with the extracted teichuronic acid in the presence of metal confirmed it to be a potent metal-complexing polymer. These results indicated that teichoic and teichuronic acids are the prime sites of metal binding in B. licheniformis walls.