Bacterial peptidoglycan polysaccharides in sterile human spleen induce proinflammatory cytokine production by human blood cells.
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Peptidoglycan (PG) is the major component of the cell wall of gram-positive bacteria. In vitro, PG isolated from conventional bacterial cultures can induce secretion of proinflammatory cytokines by human monocytes, indicating that PG may be involved in immune responses against infections by gram-positive bacteria. To investigate the biologic activity of PG in human tissues, an improved method was developed to isolate significant amounts of PG from sterile human spleen tissue. Biochemical analysis demonstrated that PG isolated from human spleen is largely intact. Human whole blood cell cultures were able to produce the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-1 and -6 after stimulation with PG isolated from human spleen. Cytokine induction was not sensitive to inhibition by polymyxin B, in contrast to lipopolysaccharide. Collectively, the data show that intact PG in sterile human tissue is biologically active and may induce local proinflammatory cytokine production. (+info)
Peptidoglycan hydrolase LytF plays a role in cell separation with CwlF during vegetative growth of Bacillus subtilis.
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Peptidoglycan hydrolase, LytF (CwlE), was determined to be identical to YhdD (deduced cell wall binding protein) by zymography after insertional inactivation of the yhdD gene. YhdD exhibits high sequence similarity with CwlF (PapQ, LytE) and p60 of Listeria monocytogenes. The N-terminal region of YhdD has a signal sequence followed by five tandem repeated regions containing polyserine residues. The C-terminal region corresponds to the catalytic domain, because a truncated protein without the N-terminal region retained cell wall hydrolase activity. The histidine-tagged LytF protein produced in Escherichia coli cells hydrolyzed the linkage of D-gamma-glutamyl-meso-diaminopimelic acid in murein peptides, indicating that it is a D,L-endopeptidase. Northern hybridization and primer extension analyses indicated that the lytF gene was transcribed by EsigmaD RNA polymerase. Disruption of lytF led to slightly filamentous cells, and a lytF cwlF double mutant exhibited extraordinary microfiber formation, which is similar to the cell morphology of the cwlF sigD mutant. (+info)
Analysis of peptidoglycan structure from vegetative cells of Bacillus subtilis 168 and role of PBP 5 in peptidoglycan maturation.
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The composition and fine structure of the vegetative cell wall peptidoglycan from Bacillus subtilis were determined by analysis of its constituent muropeptides. The structures of 39 muropeptides, representing 97% of the total peptidoglycan, were elucidated. About 99% analyzed muropeptides in B. subtilis vegetative cell peptidoglycan have the free carboxylic group of diaminopimelic acid amidated. Anhydromuropeptides and products missing a glucosamine at the nonreducing terminus account for 0.4 and 1.5%, respectively, of the total muropeptides. These two types of muropeptides are suggested to end glycan strands. An unexpected feature of B. subtilis muropeptides was the occurrence of a glycine residue in position 5 of the peptide side chain on monomers or oligomers, which account for 2.7% of the total muropeptides. This amount is, however, dependent on the composition of the growth media. Potential attachment sites for anionic polymers to peptidoglycan occur on dominant muropeptides and account for 2.1% of the total. B. subtilis peptidoglycan is incompletely digested by lysozyme due to de-N-acetylation of glucosamine, which occurs on 17.3% of muropeptides. The cross-linking index of the polymer changes with the growth phase. It is highest in late stationary phase, with a value of 33.2 or 44% per muramic acid residue, as determined by reverse-phase high-pressure liquid chromatography or gel filtration, respectively. Analysis of the muropeptide composition of a dacA (PBP 5) mutant shows a dramatic decrease of muropeptides with tripeptide side chains and an increase or appearance of muropeptides with pentapeptide side chains in monomers or oligomers. The total muropeptides with pentapeptide side chains accounts for almost 82% in the dacA mutant. This major low-molecular-weight PBP (DD-carboxypeptidase) is suggested to play a role in peptidoglycan maturation. (+info)
Expression of the Staphylococcus aureus UDP-N-acetylmuramoyl- L-alanyl-D-glutamate:L-lysine ligase in Escherichia coli and effects on peptidoglycan biosynthesis and cell growth.
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The monomer units in the Escherichia coli and Staphylococcus aureus cell wall peptidoglycans differ in the nature of the third amino acid in the L-alanyl-gamma-D-glutamyl-X-D-alanyl-D-alanine side chain, where X is meso-diaminopimelic acid or L-lysine, respectively. The murE gene from S. aureus encoding the UDP-N-acetylmuramoyl-L-alanyl-D-glutamate: L-lysine ligase was identified and cloned into plasmid vectors. Induction of its overexpression in E. coli rapidly results in abnormal morphological changes and subsequent cell lysis. A reduction of 28% in the peptidoglycan content was observed in induced cells, and analysis of the peptidoglycan composition and structure showed that ca. 50% of the meso-diaminopimelic acid residues were replaced by L-lysine. Lysine was detected in both monomer and dimer fragments, but the acceptor units from the latter contained exclusively meso-diaminopimelic acid, suggesting that no transpeptidation could occur between the epsilon-amino group of L-lysine and the alpha-carboxyl group of D-alanine. The overall cross-linking of the macromolecule was only slightly decreased. Detection and analysis of meso-diaminopimelic acid- and L-lysine-containing peptidoglycan precursors confirmed the presence of L-lysine in precursors containing amino acids added after the reaction catalyzed by the MurE ligase and provided additional information about the specificity of the enzymes involved in these latter processes. (+info)
Spore peptidoglycan structure in a cwlD dacB double mutant of Bacillus subtilis.
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Bacillus subtilis cwlD and dacB mutants produce spore peptidoglycan (PG) with increased cross-linking but with little change in spore core hydration compared to the wild type. A cwlD dacB double mutant produced spores with a two- to fourfold greater increase in PG cross-linking and novel muropeptides containing glycine residues but no significant changes in spore resistance or core hydration. (+info)
Modulation of the immune response by a synthetic adjuvant and analogs.
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N-Acetylmuramyl-L-alanyl-D-isoglutamine increases the humoral immune response of mice when given in aqueous media instead of the usual water-in-oil emulsions. Moreover, this compound is adjuvant active even by the oral route. In view of studying the relation between chemical structure and biological activity, several synthetic analogs were tested. The immune response could be modulated according to chemical modifications, and the synthetic analog with D- in place of L-alanine was shown to inhibit the immune response. (+info)
Biosynthesis of peptidoglycan in Pseudomonas aeruginosa. 1. The incorporation of peptidoglycan into the cell wall.
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Ether-treated cells of Pseudomonas aeruginosa catalyze the formation of crosslinked peptidoglycan from the two nucleotide precursors uridinediphospho-N-acetylglucosamine and uridinediphospho-N-acetylmuramyl-L-alanyl-D-gamma-glutamyl-meso-diaminopimelyl-D- alanyl-D-alanine. The main enzymatic reactions of biosynthesis were similar to those found in Escherichia coli. Part of the reaction products were soluble in 4% sodium dodecylsulfate whereas the other part was covalently bound to the preexisting cell wall peptidoglycan sacculus. The incorporation into cell wall is carried out by a transpeptidation reaction in which the nascent peptidoglycan functions mainly as the donor and the preexisting one as acceptor. The detergent-soluble peptidoglycan is composed of partially crosslinked peptidoglycan strands as well as low-molecular-weight peptidoglycan fragments. Pulse-chase biosynthesis experiments show that the detergent-soluble peptidoglycan is an intermediate that eventually becomes covalently bound to the wall. The DD-carboxypeptidase activity of P. aeruginosa is membrane-bound and does not hydrolyse C-terminal D-alanine residues from the L-lysine-containing nucleotide-precursor analogue. An LD-carboxypeptidase was also detected in P. aeruginosa. (+info)
Bacterial cell wall-induced arthritis: chemical composition and tissue distribution of four Lactobacillus strains.
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To study what determines the arthritogenicity of bacterial cell walls, cell wall-induced arthritis in the rat was applied, using four strains of Lactobacillus. Three of the strains used proved to induce chronic arthritis in the rat; all were Lactobacillus casei. The cell wall of Lactobacillus fermentum did not induce chronic arthritis. All arthritogenic bacterial cell walls had the same peptidoglycan structure, whereas that of L. fermentum was different. Likewise, all arthritogenic cell walls were resistant to lysozyme degradation, whereas the L. fermentum cell wall was lysozyme sensitive. Muramic acid was observed in the liver, spleen, and lymph nodes in considerably larger amounts after injection of an arthritogenic L. casei cell wall than following injection of a nonarthritogenic L. fermentum cell wall. The L. casei cell wall also persisted in the tissues longer than the L. fermentum cell wall. The present results, taken together with those published previously, underline the possibility that the chemical structure of peptidoglycan is important in determining the arthritogenicity of the bacterial cell wall. (+info)