Initial reactions in biosynthesis of teichuronic acid of Micrococcus lysodeikticus cell walls

Structural Identification of Lipid-α: A Glycosyl Lipid Involved in Oligo- And Polysaccharides Metabolism in Streptococcus agalactiae (Group B Streptococcus)

Streptococcus agalactiae (group B Streptococcus, GBS) is a gram-positive bacterium that is an asymptomatic colonizer commonly found in the gastrointestinal and genitourinary tract of healthy adults. GBS is also the most common cause of life-threatening bacterial infections in newborns and is emerging as a pathogen in immunocompromised and diabetic adults. The GBS cell wall and covalently linked capsular polysaccharides (CPS) are vital to the protection of the bacterial cell and act as virulence factors. GBS-CPS have been successfully used to produce conjugate vaccines for all currently identified GBS serotypes. However, the mechanisms of biosynthesis and assembly of CPS and the other cell wall components remain poorly defined due to their complex surface structures. In this biosynthetic study of the GBS cell wall-CPS complex, glycolipids with varying lengths of glycosyl-chains were discovered. Among those, one of the smallest glycolipids (named GBS Lipid-α) was structurally characterized. Lipid-α is involved in GBS saccharide metabolism and presumably acts as a glycosyl acceptor to elongate the glycosyl chain. GBS Lipid-α was determined to be a 3-monosaccharide 1,2 acyl glycerol with a molecular mass in the range of m/z = 724-808. GBS Lipid-α is highly heterogenic with various acyl groups and glycosyl moieties. This knowledge will pave the way for future studies to elucidate the entire metabolic pathway and genes involved. The Lipid-α pathway may also exist in other bacterial species and has the potential to be a biomarker for future drug development.

The biosynthesis of peptidoglycan lipid-linked intermediates

The biosynthesis of bacterial cell wall peptidoglycan is a complex process involving many different steps taking place in the cytoplasm (synthesis of the nucleotide precursors) and on the inner and outer sides of the cytoplasmic membrane (assembly and polymerization of the disaccharide-peptide monomer unit, respectively). This review summarizes the current knowledge on the membrane steps leading to the formation of the lipid II intermediate, i.e. the substrate of the polymerization reactions. It makes the point on past and recent data that have significantly contributed to the understanding of the biosynthesis of undecaprenyl phosphate, the carrier lipid required for the anchoring of the peptidoglycan hydrophilic units in the membrane, and to the characterization of the MraY and MurG enzymes which catalyze the successive transfers of the N-acetylmuramoyl-peptide and N-acetylglucosamine moieties onto the carrier lipid, respectively. Enzyme inhibitors and antibacterial compounds interfering with these essential metabolic steps and interesting targets are presented.

Colicin M Exerts Its Bacteriolytic Effect via Enzymatic Degradation of Undecaprenyl Phosphate-linked Peptidoglycan Precursors

Colicin M was earlier demonstrated to provoke Escherichia coli cell lysis via inhibition of cell wall peptidoglycan (murein) biosynthesis. As the formation of the O-antigen moiety of lipopolysaccharides was concomitantly blocked, it was hypothesized that the metabolism of undecaprenyl phosphate, an essential carrier lipid shared by these two pathways, should be the target of this colicin. However, the exact target and mechanism of action of colicin M was unknown. Colicin M was now purified to near homogeneity, and its effects on cell wall peptidoglycan metabolism reinvestigated. It is demonstrated that colicin M exhibits both in vitro and in vivo enzymatic properties of degradation of lipid I and lipid II peptidoglycan intermediates. Free undecaprenol and either 1-pyrophospho-MurNAc-pentapeptide or 1-pyrophospho-MurNAc-(pentapeptide)-Glc-NAc were identified as the lipid I and lipid II degradation products, respectively, showing that the cleavage occurred between the lipid moiety and the pyrophosphoryl group. This is the first time such an activity is described. Neither undecaprenyl pyrophosphate nor the peptidoglycan nucleotide precursors were substrates of colicin M, indicating that both undecaprenyl and sugar moieties were essential for activity. The bacteriolytic effect of colicin M therefore appears to be the consequence of an arrest of peptidoglycan polymerization steps provoked by enzymatic degradation of the undecaprenyl phosphate-linked peptidoglycan precursors.

The biology of colicin M

This communication summarizes our present knowledge of colicin M, an unusual member of the colicin group. The gene encoding colicin M, cma, has been sequenced and the protein isolated and purified. With a deduced molecular size of 29,453 Da, colicin M is the smallest of the known colicins. The polypeptide can be divided into functional domains for cell surface receptor binding, uptake into the cell, and killing activity. To kill, the colicin must enter from outside the cell. Colicin M blocks the biosynthesis of both peptidoglycan and O-antigen by inhibiting regeneration of the bactoprenyl-P carrier lipid. Autolysis occurs as a secondary effect following inhibition of peptidoglycan synthesis. Colicin M is the only colicin known to have such a mechanism of action. Immunity to this colicin is mediated by the cmi gene product, a protein of 13,890 Da. This cytoplasmic membrane protein confers immunity by binding to and thus neutralizing the colicin. Cmi shares properties with both immunity proteins of the pore-forming and the cytoplasmically active colicins. Genes for the colicin and immunity protein are found next to each other, but in opposite orientation, on pColM plasmids. The mechanism of colicin M release is not known.

Biosynthetic elongation of isolated teichuronic acid polymers via glucosyl- and N-acetylmannosaminuronosyltransferases from solubilized cytoplasmic membrane fragments of Micrococcus luteus

Cytoplasmic membrane fragments of Micrococcus luteus catalyze in vitro biosynthesis of teichuronic acid from uridine diphosphate D-glucose (UDP-glucose), uridine diphosphate N-acetyl-D-mannosaminuronic acid (UDP-ManNAcA), and uridine diphosphate N-acetyl-D-glucosamine. Membrane fragments solubilized with Thesit (dodecyl alcohol polyoxyethylene ether) can utilize UDP-glucose and UDP-ManNAcA to effect elongation of teichuronic acid isolated from native cell walls. When UDP-glucose is the only substrate supplied, the detergent-solubilized glucosyltransferase incorporates a single glucosyl residue onto each teichuronic acid acceptor. When both UDP-glucose and UDP-ManNAcA are supplied, the glucosyltransferase and the N-acetylmannosaminuronosyltransferase act cooperatively to elongate the teichuronic acid acceptor by multiple additions of the disaccharide repeat unit. As shown by polyacrylamide gel electrophoresis, low-molecular-weight fractions of teichuronic acid are converted to higher-molecular-weight polymers by the addition of as many as 17 disaccharide repeat units.

Polymer length of teichuronic acid released from cell walls of Micrococcus luteus

Teichuronic acid released from its phosphodiester linkage to peptidoglycan in the cell walls of Micrococcus luteus by mild acid treatment is resolved into a ladderlike series of bands by electrophoresis on polyacrylamide gels in the presence of borate. Each band of the ladder differs from its nearest neighbor by one disaccharide repeat unit, ----4)-2-acetamido-2-deoxy-beta-D-mannopyranuronosyl-(1----6)- alpha-D-glucopyranosyl-(1-. Acid-fragmented teichuronic acid, after conversion to the phenylamine derivative, was fractionated by preparative-scale molecular sieve column chromatography, which produced a series of elution peaks. Fast-atom-bombardment mass spectrometry of the smallest member of the series determined its molecular weight and established its identity as the phenylamine derivative of one disaccharide repeat unit of teichuronic acid. Homologous fractions of the same series were used to index the ladder of bands obtained by polyacrylamide gel electrophoresis from samples containing a more extensive distribution of polymer lengths. Nearly native teichuronic acid consists of polymers with a broad range of molecular sizes ranging from 20 to 55 disaccharide units. The most abundant species are those which have 25 to 40 repeat units. Prolonged treatment of teichuronic acid with the acid conditions used to release it from peptidoglycan causes gradual fragmentation of the teichuronic acid.

Teichuronic acid reducing terminal N-acetylglucosamine residue linked by phosphodiester to peptidoglycan of Micrococcus luteus

Teichuronic acid-peptidoglycan complex isolated from Micrococcus luteus cells by lysozyme digestion in osmotically stabilized medium was treated with mild acid to cleave the linkage joining teichuronic acid to peptidoglycan. This labile linkage was shown to be the phosphodiester which joins N-acetylglucosamine, the residue located at the reducing end of the teichuronic acid, through its anomeric hydroxyl group to a 6-phosphomuramic acid, a residue of the glycan strand of peptidoglycan. 31P nuclear magnetic resonance spectroscopy of the lysozyme digest of cell walls demonstrated the presence of a phosphodiester which was converted to a phosphomonoester by the conditions which released teichuronic acid from cell walls. Reduction of acid-liberated reducing end groups by NaB3H4 followed by complete acid hydrolysis yielded [3H] glucosaminitol from the true reducing end residue of teichuronic acid and [3H]glucitol from the sites of fragmentation of teichuronic acid. The amount of N-acetylglucosamine detected was approximately stoichiometric with the amount of phosphate in the complex. Partial fragmentation of teichuronic acid provides an explanation of the previous erroneous identification of the reducing end residue.

Biosyntheses of galactosyl lipids and polysaccharide in Streptococcus mutans

The syntheses of galactosylphospholipids and a galactose-containing polymer were observed when radio-labeled UDP-galactose was incubated with the membrane enzymes prepared from a strain of Streptococcus mutans, FA-1. The lipids were resolved into two components, lipids-1 and -2, by thin-layer and DEAE-cellulose column chromatographies. In the latter chromatography, lipid-1 was eluted by 0.0075 M and lipid-2 by 0.18 M ammonium acetate. The syntheses of lipids-1 and -2 were strongly inhibited by UDP and UMP, respectively. Both lipids-1 and -2 were degraded by mild acid, but were stable to mild alkaline hydrolysis. These results, together with their mobilities on thin-layer chromatography, suggest that lipid-1 is a galactosylphosphorylundecaprenol, and lipid-2 is a galactosylpyrophosphorylundecaprenol. When UDP-galactose was incubated with radiolabeled undecaprenol and ATP in the presence of membrane enzymes, lipids with thin-layer chromatographic mobilities of lipid-1 and lipid-2 were observed. The phosphate-to-galactose ratios in lipid-1 and lipid-2 were determined to be 1:1 and 2:1, respectively. These results indicated that lipid-1 and lipid-2 formed are galactosylmonophosphorylundecaprenol and galactosylpyrophosphorylundecaprenol, respectively. The polymer formed was eluted from the DEAE-cellulose column with a low concentration of salts (less than 0.1 M), suggesting that it is probably a polysaccharide, but not a lipoteichoic acid or teichoic acid-type polymer. In order to identify the sugars present in the polymer synthesized, the polymer purified by Sephadex G-50 and DEAE-cellulose column chromatographies was subjected to acid hydrolysis followed by NaB3H4 reduction and paper chromatographic analysis. [3H]Galactitol and a small amount of [3H]galactosaminitol were detected. This result suggests that the polymer is a nascent polysaccharide containing mainly galactose and a small amount of galactosamine, which probably derived from N-acetylgalactosamine during acid hydrolysis of the polymer.

Structural studies on the minor teichoic acid of Bacillus coagulans AHU 1631

The minor teichoic acid linked to glycopeptide was isolated from lysozyme digests of Bacillus coagulans AHU 1631 cell walls, and the structure of the teichoic acid moiety and its junction with the peptidoglycan were studied. Hydrolysis of the teichoic-acid--glycopeptide complex with hydrogen fluoride gave a nonreducing oligosaccharide composed of glucose, galactose and glycerol in a molar ratio of 3:1:1 which was presumed to be dephosphorylated repeating units of the polymer chain. From the results of structural analysis involving NaIO4 oxidation, methylation and acetolysis, the above fragment was characterized as glucosyl(beta 1----3)glucosyl(beta 1----6)galactosyl(beta 1----6)glucosyl(alpha 1----1/3)glycerol. In addition, the Smith degradation of the complex yielded a phosphorus-containing fragment identified as glycerol-P-6-glucosyl(beta 1----1/3)glycerol. These results led to the most likely structure for the repeating units of the teichoic acid, -6[glucosyl(beta 1----3)]glucosyl(beta 1----6)galactosyl(beta 1----6)glucosyl(alpha 1----1/3)glycerol-P-. The minor teichoic acid, just like the major teichoic acid bound to the linkage unit, was released by heating the cell walls at pH 2.5. The mild alkaline hydrolysis of the minor teichoic acid after reduction with NaB3H4 gave labeled saccharides characterized as glucosyl(beta 1----6)galactitol and glucosyl(beta 1----3)glucosyl(beta 1----6)galactitol, together with a large amount of the unlabeled repeating units of the teichoic acid chain. Thus, the minor teichoic acid chain is believed to be directly linked to peptidoglycan at the galactose residue of the terminal repeating unit without a special linkage sugar unit.

Characterization of three intermediates in the biosynthesis of teichuronic acid of Micrococcus luteus

Teichuronic acid, the Micrococcus luteus cell wall polysaccharide which consists of D-glucose and N-acetyl-D-mannosaminuronic acid, is synthesized in vitro from uridine diphosphate N-acetyl-D-glucosamine, uridine diphosphate N-acetyl-D-mannosaminuronic acid, and uridine diphosphate D-glucose in a series of reactions catalyzed by a particulate enzyme preparation. Several lipid-linked intermediates are formed, of which the first three are called components A, B, and C. The formation of these intermediates is inhibited by tunicamycin. The lipid moiety of the intermediates is approximately 95% undecaprenol and 5% dodecaprenol as determined by mass spectrometry. The oligosaccharide moieties of components B and C are the disaccharide, N-acetyl-D-mannosaminuronyl-(1,3)-N-acetyl-D-glucosamine, and the trisaccharide, N-acetyl-D-mannosaminuronyl-(1,4)-N-acetyl-D-mannosaminuronyl++ +-(1, 3)-N-acetyl-D-glucosamine, respectively, as determined by the complete degradation of the former and partial degradation of the latter by the alkaline beta-elimination reaction. The saccharide and lipid moieties of the intermediates are linked through pyrophosphate. Thus, component A is P1-N-acetyl-alpha-D-glucosaminyl P2-undecaprenyl diphosphate, component B is P1-N-acetyl-D-mannosaminuronyl-(1, 3)-N-acetyl-alpha-D-glucosaminyl P2-undecaprenyl diphosphate, and component C is P1-N-acetyl-D-mannosaminuronyl-(1,4)-N-acetyl-D-mannosaminurony l-(1, 3)-N-acetyl-alpha-D-glucosaminyl P2-undecaprenyl diphosphate.

Biosynthesis of N-acetylmannosaminuronic-acid-containing cell-wall polysaccharide of Bacillus subtilis

The particulate enzyme from Bacillus subtilis AHU 1031 catalyzed the synthesis of a polysaccharide and glycolipids from UDP-N-acetylmannosaminuronic acid (UDP-ManNAcUA), UDP-N-acetylglucosamine (UDP-GlcNAc), and UDP-glucose (UDP-Glc). The polysaccharide synthesis required UDP-ManNAcUA and UDP-GlcNAc, proceeded optimally at pH 8.5 and in the presence of 5 mM MgCl2 and 2.5 mM dithiothreitol, and was stimulated by the addition of UDP-Glc. The molar ratio of ManNAcUA, GlcNAc, and Glc incorporated into polysaccharide was calculated to be 1:1:1.8 from chemical analysis involving reduction with water soluble carbodiimide; its relative molecular mass was estimated to be 12000. The analysis of Smith degradation products revealed that the polysaccharide backbone is composed of repeating trisaccharide units comprising ManNAcUA, GlcNAc, and Glc. Based on the data regarding the time course of the incorporation of glucose into the polysaccharide, extra glucose seems to be attached to the polysaccharide backbone as lateral branches. The saccharide moieties of the glycolipids were identified as GlcNAc, ManNAcUA-GlcNAc, and Glc-ManNAcUA-GlcNAc from several analytical criteria. The addition of antibiotic 24010, a tunicamycin-like antibiotic, at 10 micrograms/ml resulted in almost complete inhibition of the synthesis of glycolipids and polysaccharide. It is therefore concluded that the glycolipids function as intermediates in polysaccharide formation. Incubation of the ManNAcUA-GlcNAc-linked lipid. (labeled in the ManNAcUA moiety) with the particulate enzyme and UDP-Glc resulted incorporation of radioactivity into a trisaccharide-linked lipid and a polysaccharide. These results suggest that the particulate enzyme utilizes the trisaccharide moiety of the Glc-ManNAcUA-GlcNAc-linked lipid for the elongation of the main polysaccharide chain presumed to be cell wall acidic polysaccharide of this strain.

The primary structure of teichuronic acid in Bacillus subtilis AHU 1031

Structural studies were carried out on the acidic polysaccharide fraction obtained from lysozyme digest of the cell walls of Bacillus subtilis AHU 1031. The polysaccharide fraction contained N- acetylmannosaminuronic acid ( ManNAcA ), N-acetylglucosamine (GlcNAc), glucose, glycerol and phosphorus in a molar ratio of 2:2:4:1:1, together with glycopeptide components. The results of analyses involving Smith degradation, chromium trioxide oxidation, methylation and proton magnetic resonance spectroscopy led to the conclusion that the backbone chain of the polysaccharide has the repeating unit----6)Glc(alpha 1----3/4) ManNAcA (beta 1----4)GlcNAc(beta 1----. About 50% of the N-acetylglucosamine residues in the backbone chain seem to be substituted at C-3 by the glycosidic branches, glycerol phospho-6-glucose, while the other half seem to be substituted by glucose.

Lipopolymers, isoprenoids, and the assembly of the gram-positive cell wall

Several lines of evidence suggest that Gram-positive bacterial cell surface polymers are synthesized by stepwise addition of polymer subunits to an amphipathic acceptor. In the case of membrane-bound lipopolymers such as mannan and lipoteichoic acid, the finished product may be covalently linked to a lipid anchor. In the case of polymers that are transferred into preexisting cell wall, such as teichoic acid and peptidoglycan, two alternative fates might be possible: (1) transfer into wall with concomitant or later cleavage of the lipid anchor, with recycling of the lipid anchor or secretion of the lipid anchor into the growth medium, and (2) transfer into wall without cleavage of the lipid anchor, resulting in maintenance of the covalent relationship between lipid anchor and polymer chain. In the latter case, a close relationship should be established between the cell wall and the plasma membrane. A number of Gram-positive bacteria have been shown to be resistant to plasmolysis. Therefore, a model for the assembly of the Gram-positive cell wall is proposed which takes into account a role for lipopolymeric intermediates and which views the establishment of resistance to plasmolysis as the natural consequence of such a mechanism.

Biosynthesis of a D-glucosyl polyisoprenyl diphosphate in particulate preparations of Micrococcus lysodeikticus

Particulate fractions of Micrococcus lysodeikticus incubated with UDP-D-[14C]glucose incorporated radioactivity into a chloroform - methanol-soluble, low-mol. wt. compound, and into a polymer. The low-mol. wt. compound consisted of a glucolipid that was extremely labile to mild acid hydrolysis with the formation of D-[14C]glucose, and to mild alkali, yielding 14C-labeled alpha-D-glucopyranose 1,2-phosphate and D-glucose 2-phosphate. The labeled glucolipid was eluted from a DEAE-cellulose column at a salt concentration higher than that required by synthetic ficaprenyl (D-glucopyranosyl phosphate), and it migrated more slowly than the latter compound in t.l.c. Formation of the glucolipid was stimulated by exogenous ficaprenyl phosphate, but not by C55-dolichyl phosphate. These results suggest that the [14C]glucolipid has the characteristic properties of a polyisoprenyl glucosyl diphosphate.

Structure of teichoic-acid--glycopeptide complexes from cell walls of Bacillus cereus AHU 1030

From lysozyme digests of N-acetylated cell walls of Bacillus cereus AHU 1030, two acidic polymer fractions with molecular weights of about 24000 and 45000 were isolated by ion-exchange chromatography and gel chromatography. These polymer fractions, containing glycerol, phosphorus and glucose in a molar ratio of 1.00:1.00:0.85 together with small amounts of glycopeptide components and mannosamine, were characterized as teichoic-acid-glycopeptide complexes with one and two teichoic acid chains made of 60-65 repeating glycerol phosphate units that were mostly glucosylated. Mild alkali treatment of the complexes yielded a disaccharide-linked glycopeptide. The disaccharide was liberated from the glycopeptide by mild acid treatment and identified as N-acetylmannosaminyl(beta 1 leads to 4)N-acetylglucosamine. On the other hand, the same disaccharide linked to the teichoic acid chain was obtained by direct heating of the cell walls at pH 2.5. These results lead to a conclusion that in the cell walls of this strain the glycerol teichoic acid chain is attached to the glycan chain of peptidoglycan through this disaccharide unit. The disaccharide is linked at its reducing and nonreducing ends to the glycan chain and the teichoic acid chain, respectively, through phosphodiester bridges.

Structural and biosynthetic studies on linkage region between poly(galactosylglycerol phosphate) and peptidoglycan in Bacillus coagulans

The HF treatment of teichoic acid-glycopeptide complexes isolated from lysozyme digests of Bacillus coagulans AHU 1366 cell walls gave a disaccharide, glucosyl beta (1 leads to 4)N-acetylglucosamine, along with dephosphorylated repeating units of the teichoic acid chain, galactosyl alpha (1 leads to 2) glycerol. Mild alkali treatment of the complexes yielded the disaccharide linked to glycopeptide, whereas direct heating of the cell walls at pH 2.5 yielded the same disaccharide linked to teichoic acid. The Smith degradation of the complexes revealed that the galactose residue is a component of backbone chain. Thus it is concluded that this disaccharide is involved in the linkage region between poly(galactosylglycerol phosphate) and peptidoglycan in cell walls. Membrane-catalyzed synthesis of this disaccharide on a lipid followed by transfer of glycerol phosphate from CDP-glycerol to the disaccharide-linked lipid in the absence or in the presence of UDP-galactose also supports this conclusion.

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.

The biosynthesis and linkage of teichuronic acid to peptidoglycan in Bacillus licheniformis

Membrane and wall-membrane preparations of Bacillus licheniformis 94 will, if supplied with the appropriate precursors, synthesize teichuronic acid and link it to peptidoglycan although teichuronic acid is absent from walls of this organism. B. licheniformis 94 lacks phosphoglucomutase activity and therefore cannot synthesize the precursor UDPglucuronic acid. The initial reaction of teichuronic acid biosynthesis is catalysed by a translocase and results in the formation of polyprenyl-diphospho-N-acetylgalactosamine and the release of UMP. This reaction is not inhibited by tunicamycin. The disaccharide repeating unit of the polymer is then formed by the transfer of glucuronic acid from UDPglucuronic acid with the release of UDP. Polymerization of the repeating units occurs by incorporation of new units at the reducing terminus of the growing teichuronic acid chain and the release of polyprenyl diphosphate. The subsequent dephosphorylation of the lipid diphosphate for reuse in the biosynthesis cycle is inhibited by bacitracin. Linkage to peptidoglycan occurs by the formation of a phosphodiester bond between the reducing N-acetylgalactosamine terminus of the teichuronic acid chain and a 6-hydroxyl group of a muramic acid residue in the glycan of peptidoglycan. Wall-membrane preparations synthesizing teichuronic acid, poly(glycerol phosphate) teichoic acid and peptidoglycan link the teichuronic and teichoic acids to different glycan chains.

Distribution of mannosamine and mannosaminuronic acid among cell walls of Bacillus species

The distribution of mannosamine, mannosaminuronic acid, and the enzymes responsible for the formation of these saccharides was studied in nine species (18 strains) of Bacillus. Whereas UDP-N-acetylglucosamine 2-epimerase activity was detected in all of the strains examined, UDP-N-acetylmannosamine dehydrogenase, as well as the activity incorporating N-acetylmannosaminuronic acid residues from UDP-N-acetylmannosaminuronic acid into polymer, was found only in four strains of B. megaterium and one strain each of B. subtilis and B. polymyxa. The cell walls prepared from the six above-named strains were shown to contain mannosaminuronic acid in amounts of 135 to 245 nmol/mg. In contrast, mannosamine had a wide distribution. The cell walls from two strains of B. cereus and one strain each of B. circulans, B. polymyxa, B. sphaericus, and B. cereus subsp. mycoides contained mannosamine in amounts of 370 to 470 nmol/mg. In addition, the cell walls from five strains of B. subtilis, two strains of B. megaterium, and one strain each of B. cereus. B. coagulans, and B. licheniformis also contained this amino sugar in amounts as small as 10 to 35 nmol/mg. On the basis of analytical data, it is suggested that the mannosamine present in small amounts may be a common constituent of linkage units between peptidoglycan and other cell wall components such as glycerol teichoic acid.

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.