Selective extraction of polymers from cell walls of gram-positive bacteria

Alzheimer disease

Alzheimer disease (AD) is biologically defined by the presence of β-amyloid-containing plaques and tau-containing neurofibrillary tangles. AD is a genetic and sporadic neurodegenerative disease that causes an amnestic cognitive impairment in its prototypical presentation and non-amnestic cognitive impairment in its less common variants. AD is a common cause of cognitive impairment acquired in midlife and late-life but its clinical impact is modified by other neurodegenerative and cerebrovascular conditions. This Primer conceives of AD biology as the brain disorder that results from a complex interplay of loss of synaptic homeostasis and dysfunction in the highly interrelated endosomal/lysosomal clearance pathways in which the precursors, aggregated species and post-translationally modified products of Aβ and tau play important roles. Therapeutic endeavours are still struggling to find targets within this framework that substantially change the clinical course in persons with AD.

Two Glycosyl 1-Phosphate Polymers and Teichulosonic Acid from Glutamicibacter protophormiae VKM Ac-2104T Cell Wall

Two glycosyl 1-phosphate polymers containing monoglycosyl 1-phosphate, -6)-α-D-Glcp-(1-P-, and diglycosyl 1-phosphate, -6)-α-D-GalpNAc-(1→6)-α-D-GlcpNAc-(1-P-, in the repeating unit were identified in the cell wall of Glutamicibacter protophormiae VKM Ac-2104^T (formerly, Arthrobacter protophormiae). The structures of these polymers were described for the first time in prokaryotes. Teichulosonic acid, the third identified polymer, with 3-deoxy-D-glycero-α-D-galacto-non-2-ulopyranosonic acid (Kdn) and β-D-glucopyranose residues in the main chain, →6)-β-D-Glcp-(1→8)-α-Kdn-(2→, has been previously detected in a number of actinobacteria. The structures of these glycopolymers were established based on the results of chemical analysis and one-dimensional ¹H, ¹³C, and ³¹P NMR spectroscopy using two-dimensional homonuclear (¹H,¹H COZY, TOCSY, ROESY) and heteronuclear (¹H,¹³C HSQC, HSQC-TOCSY, HMBC, and ¹H,³¹P HMBC) techniques.

Identification of Streptomyces coelicolor M145 genomic region involved in biosynthesis of teichulosonic acid-cell wall glycopolymer

The cell wall of the model actinomycete Streptomyces coelicolor M145 has recently been shown to contain the novel glycopolymer teichulosonic acid. The major building block of this polymer is 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (Kdn), suggesting initial clues about the genetic control of biosynthesis of this cell wall component. Here, through genome mining and gene knockouts, we demonstrate that the sco4879-sco4882 genomic region of S. coelicolor M145 is necessary for biosynthesis of teichulosonic acid. Specifically, mutants carrying individual knockouts of sco4879, sco4880 and sco4881 genes do not produce Kdn-containing glycopolymer and instead accumulate the minor cell wall component poly(diglycosyl 1-phosphate). Our studies provide evidence that this region is at least partly responsible for biosynthesis of Kdn, whereas flanking genes might control the other steps of teichulosonic acid formation.

Phosphate-containing cell wall polymers of bacilli

Anionic phosphate-containing cell wall polymers of bacilli are represented by teichoic acids and poly(glycosyl 1-phosphates). Different locations of phosphodiester bonds in the main chain of teichoic acids as well as the nature and combination of the constituent structural elements underlie their structural diversity. Currently, the structures of teichoic acids of bacilli can be classified into three types, viz. poly(polyol phosphates) with glycerol or ribitol as the polyol; poly(glycosylpolyol phosphates), mainly glycerol-containing polymers; and poly(acylglycosylglycerol phosphate), in which the components are covalently linked through glycosidic, phosphodiester, and amide bonds. In addition to teichoic acids, poly(glycosyl 1-phosphates) with mono- and disaccharide residues in the repeating units have been detected in cell walls of several Bacillus subtilis and Bacillus pumilus strains. The known structures of teichoic acids and poly(glycosyl 1-phosphates) of B. subtilis, B. atrophaeus, B. licheniformis, B. pumilus, B. stearothermophilus, B. coagulans, B. cereus as well as oligomers that link the polymers to peptidoglycan are surveyed. The reported data on the structures of phosphate-containing polymers of different strains of B. subtilis suggest heterogeneity of the species and may be of interest for the taxonomy of bacilli to allow differentiation of closely related organisms according to the "structures and composition of cell wall polymers" criterion.

Bacillus subtilis metabolism and energetics in carbon-limited and excess-carbon chemostat culture

The energetic efficiency of microbial growth is significantly reduced in cultures growing under glucose excess compared to cultures growing under glucose limitation, but the magnitude to which different energy-dissipating processes contribute to the reduced efficiency is currently not well understood. We introduce here a new concept for balancing the total cellular energy flux that is based on the conversion of energy and carbon fluxes into energy equivalents, and we apply this concept to glucose-, ammonia-, and phosphate-limited chemostat cultures of riboflavin-producing Bacillus subtilis. Based on [U-(13)C(6)]glucose-labeling experiments and metabolic flux analysis, the total energy flux in slow-growing, glucose-limited B. subtilis is almost exclusively partitioned in maintenance metabolism and biomass formation. In excess-glucose cultures, in contrast, uncoupling of anabolism and catabolism is primarily achieved by overflow metabolism, while two quantified futile enzyme cycles and metabolic shifts to energetically less efficient pathways are negligible. In most cultures, about 20% of the total energy flux could not be assigned to a particular energy-consuming process and thus are probably dissipated by processes such as ion leakage that are not being considered at present. In contrast to glucose- or ammonia-limited cultures, metabolic flux analysis revealed low tricarboxylic acid (TCA) cycle fluxes in phosphate-limited B. subtilis, which is consistent with CcpA-dependent catabolite repression of the cycle and/or transcriptional activation of genes involved in overflow metabolism in the presence of excess glucose. ATP-dependent control of in vivo enzyme activity appears to be irrelevant for the observed differences in TCA cycle fluxes.

Incorporation of [2-3H]glycerol into cell surface components of Bacillus subtilis 168 and thermosensitive mutants affected in wall teichoic acid synthesis: effect of tunicamycin

A method is described for measuring the synthesis of poly(glycerol phosphate) [poly(groP)], the major wall teichoic acid (WTA), lipoteichoic acid (LTA) and phospholipid (P-lipid), through fractionation of [2-3H]glycerol ([2-3H]gro)-labelled Bacillus subtilis cells. When cultures of certain temperature-sensitive mutants defective in one of several tag genes, encoding enzymes involved in WTA synthesis, were transferred to the restrictive temperature, the synthesis of WTA underwent a specific, immediate, block, while that of LTA or P-lipid proceeded unimpeded. These results, in addition to confirming the role of tag genes, demonstrated, reciprocally, the specificity of the fractionation procedure used to distinguish label in WTA from that in LTA or P-lipid. Results of analysis of other, less severely affected, tag-deficient mutants, as well as of another genetically unrelated mutant developing comparable morphological phenotypes in non-permissive conditions, are discussed in relation to a possible mechanism generating the latter phenotype. Fractionation of B. subtilis 168 cells labelled either with [2-3H]gro or with [1-14C]N-acetylglucosamine, to which tunicamycin was added at 0.5 microg ml(-1) (the MIC) revealed a specific and marked inhibition of poly(groP) as well as of poly(3-O-beta-D-glucopyranosyl-N-acetylgalactosamine 1-phosphate), the minor WTA. However, for 60 min at least, the syntheses of PG, LTA and P-lipid were barely affected.

Changes in wall teichoic acid during the rod-sphere transition of Bacillus subtilis 168

Wall teichoic acid (WTA) is essential for the growth of Bacillus subtilis 168. To clarify the function of this polymer, the WTAs of strains 168, 104 rodB1, and 113 tagF1 (rodC1) grown at 32 and 42 degrees C were characterized. At the restrictive temperature, the rodB1 and tagF1 (rodC1) mutants undergo a rod-to-sphere transition that is correlated with changes in the WTA content of the cell wall. The amount of WTA decreased 33% in strain 104 rodB1 and 84% in strain 113 tagF1 (rodC1) when they were grown at the restrictive temperature. The extent of alpha-D-glucosylation (0.84) was not affected by growth at the higher temperature in these strains. The degree of D-alanylation decreased from 0.22 to 0.10 in the rodB1 mutant but remained constant (0.12) in the tagF1 (rodC1) mutant at both temperatures. Under these conditions, the degree of D-alanylation in the parent strain decreased from 0.27 to 0.21. The chain lengths of WTA in strains 168 and 104 rodB1 grown at both temperatures were approximately 53 residues, with a range of 45 to 60. In contrast, although the chain length of WTA from the tagF1 (rodC1) mutant at 32 degrees C was similar to that of strains 168 and 104 rodB1, it was approximately eight residues at the restrictive temperature. The results suggested that the rodB1 mutant is partially deficient in completed poly(glycerophosphate) chains. The precise biochemical defect in this mutant remains to be determined. The results for strain 113 tagF1(rodC1) are consistent with the temperature-sensitive defect in the CDP-glycerol:poly(glycerophosphate) glycerophosphotransferase (H. M. Pooley, F.-X. Abellan, and D. Karamata, J. Bacteriol. 174:646-649, 1992).

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.

Morphological and cell wall alterations in thermosensitive DNA mutants of Bacillus subtilis

Incubation of thermosensitive dna mutants of Bacillus subtilis at the nonpermissive temperature results, at the cellular level, in the appearance of swellings. The study of one particular type of swelling, named "terminal balloon", reveals that the occurrence of the latter was correlated with completion of rounds of DNA replication. Morphological and autoradiographic observations reveal that (a) cell wall consists of two layers, (b) the outer layer splits at a fixed distance from the cell pole and allows the formation of a balloon contained within a single wall layer and (c) the bulk of active synthesis of cell wall is localized in the balloon area leading to the formation of a near spherical monolayer. Implications of these results for cell wall morphogenesis are discussed.

Control of teichoic acid synthesis in Bacillus licheniformis ATCC 9945

Analysis of cell walls of Bacillus licheniformis ATCC 9945 grown under phosphate limitation showed that teichoic acid could be replaced by teichuronic acid under these conditions. Teichuronic acid, however, was always present in the walls to some extent irrespective of the growth conditions. The enzymes involved in teichoic acid synthesis were investigated and the synthesis of these was shown to be repressed when the intracellular Pi level fell. CDP-glycerol pyrophosphorylase was studied in some detail and evidence is presented to show that the enzyme is inactivated under phosphate-limited conditions. The mechanism of inactivation is unknown but it has been shown that it does not require protein synthesis de novo.

Control of teichoic and teichuronic acid biosynthesis in Bacillus subtilis 168trp. Evidence for repression of enzyme synthesis and inhibition of enzyme activity

Phosphate starvation induced teichuronic acid synthesis in cells of Bacillus subtilis 168trp-which had previously been grown with excess phosphate. This induction was prevented when protein systhesis was inhibited immediately prior to phosphate starvation and under these conditions cells continued to form teichoic acid. The converse was true when phosphate was added to cells previously grown in a phosphate-limited chemostat. The increase in teichoic acid synthesis normally following phosphate addition was prevented by chloramphenicol or amino acid starvation and cells continued to make teichuronic acid. This suggestion that repression of enzyme synthesis is involved in controlling the type of wall polymer made was supported by the low levels of UDP-glucose dehydrogenase found in cells grown with excess phosphate and of CDP-glycerol pyrophosphorylase in phosphate-limited cells. The greater amounts of teichoic acid made under phosphate limitation and of teichuronic acid with excess phosphate when protein synthesis was also inhibited indicated that modulation of enzyme activity occurs. Glycerol starvation of a glycerol-requiring mutant did not derepress teichuronic acid synthesis, indicating that glycerol-containing imtermediates do not act as repressors.

Halococcus morrhuae: a sulfated heteropolysaccharide as the structural component of the bacterial cell wall

The qualitative and quantitative composition of purifed cell wall of Halococcus morrhuae CCM 859 was determined. Glucose, mannose, galactose; glucuronic and galacturonic acids; glucosamine, galactosamine, gulosaminuronic acid; acetate, glycine and sulfate are found as major constituents. The amino sugars are N-acetylated. It was not possible to fractionate the cell wall in chemically different polymers. Evidence is presented that the major cell wall polymer of this strain is a complex heterolgycan which seems, like the peptidoglycan of most bacteria, to be responsible for the rigidity and stability of the cell wall. In addition it could be proved that this heteroglycan is sulfated and therefore differs considerably from previously described bacterial cell wall polymers.

The structure of a polymer containing galactosamine from walls of Bacillus subtilis 168

Cell walls of Bacillus subtilis 168 contain a phosphorylated polysaccharide composed of N-acetylgalactosamine, glucose and phosphate. Controlled acid hydrolysis gives 3-O-beta-d-glucopyranosyl-N-acetylgalactosamine with a phosphomonoester group at the 6-position of glucose. It is likely that the polysaccharide consists of disaccharide units connected by phosphodiester residues joining the 1-position of N-acetylgalactosamine to the 6-position of glucose in the neighbouring unit.