Bacterial Cell Wall Recycling

Abstract

Cell wall recycling is a process whereby bacteria degrade their own wall during growth, recover released constituents by active transport and reutilise them either to rebuild the wall or to gain energy. Most knowledge about cell wall recycling comes from studies with the Gram‐negative bacterium Escherichia coli. Within one generation, this organism breaks down and efficiently recycles approximately 60% of the mature peptidoglycan of its side‐wall during cell elongation and approximately 30% of newly deposited septal peptidoglycan during cell division. The reason for the massive turnover of the peptidoglycan is still unclear, although many other bacteria, including Gram‐positives, have been reported to turnover their cell wall and release similar quantities of peptidoglycan fragments during growth and differentiation. Whether these fragments are also recycled is basically unknown. The presence of recycling genes on most bacterial genomes, however, suggests that cell wall recycling is a very common pathway of bacteria.

Key Concepts:

  • The peptidoglycan of the bacterial cell wall represents a single, giant, reticular macromolecule (i.e. the murein sacculus) that encases the entire bacterial cell.

  • The peptidoglycan cell wall has to be cleaved continuously during growth to allow cell expansion by insertion of new wall material.

  • Bacteria possess a huge and partially redundant set of cell wall lytic enzymes that potentially target every covalent bond connecting the amino acid and amino sugar building blocks within the peptidoglycan network (cell wall lytic complement).

  • Many bacteria release a great amount of cell wall material during bacterial growth (cell elongation and division). The reason for the massive turnover of approximately 50% of the existing peptidoglycan in one generation is still unclear.

  • Bacteria eventually recover cell wall turnover fragments. The pathways for the continuous recycling of peptidoglycan have been explored in great detail in Escherichia coli.

  • Cell wall recycling in Gram‐positive bacteria has been appreciated just recently and apparently differs from the E. coli paradigm as well as between Gram‐positive species.

  • Cell wall‐derived peptidoglycan fragments function as potent biological effectors. They are involved in sensing the cell wall and growth state, inducing expression of antibiotic resistance genes, and triggering cell differentiation and resuscitation of dormant cells.

Keywords: peptidoglycan recycling; cell wall turnover; muropeptide rescue; muropeptide signalling; β‐lactamase induction; murein tripeptide; N‐acetylmuramic acid (MurNAc); anhydromuramic acid; lysozyme; lytic transglycosylases

Figure 1.

The structure of peptidoglycan, the stabilising macromolecule of the bacterial cell wall and structural variations within bacteria. As the name indicates, the peptidoglycan is constructed of peptides (amino acids are boxed) and glycans (polysaccharide chains) that are interconnected. Glycan chains of variable length are composed of alternating, β‐1‐4 glycosidically linked amino sugars, N‐acetyl glucosamine (GlcNAc) and N‐acetylmuramic acid (MurNAc). These may be modified by partial O‐acetylation of the C6 hydroxyl groups (s. upper strand) or N‐deacetylation of the C2 acetamido groups (s. lower strand). The unique bacterial amino sugar MurNAc serves as the branching point within the peptidoglycan network, interconnecting the glycan chains via short peptide bridges that attached to the ether‐linked d‐lactic acid substituent. There is a great variability in the composition and structure of the stem peptides of the peptidoglycan but they usually contain amino acids of the d‐enantiomeric form (d‐alanine, d‐Ala and d‐glutamate, d‐Glu) and di‐basic amino acids (meso‐diaminopimelic acid, DAP, in E. coli and other Gram‐type negative bacteria as well as in Bacilli and Clostridiae; l‐lysin, l‐Lys, in most other Gram‐type positive bacteria, and in some cases l,l‐Dap or l‐ornithine). d‐ and l‐amino acids in the peptidoglycan network are connected in such a way that l‐d‐l‐d‐d‐peptides are formed, which are insensitive to ‘normal’ l‐l‐peptidases/proteases. Notably, the d‐Glu in these stem peptides is linked through an isopeptide bond via its γ‐carboxylic acid. Both, d‐Glu and DAP, may be amidated at their d‐α‐carboxylic acid. Most Gram‐positive bacteria connect two stem peptides via a linker unit, such as a pentaglycine bridge (Gly5) in Staphylococcus aureus, an l‐Ala‐l‐Ala bridge in Enterococcus faecalis, or a d‐aspartate, d‐Asp (eventually amidated at the α‐carboxylic acid) in Lactococcus lactis and Enterococcus faecium. Gram‐negative bacteria as well as Bacillus and Clostridium sp. use direct crosslinks, connecting the amino group of the d‐centre of DAP3 with the carboxylic acid of the forth amino acid (d‐Ala4) of another strand, generating a d‐d‐peptide bond (d,d‐crosslink). These crosslinks are formed concomitantly with the cleavage of a terminal d‐Ala4d‐Ala5 bond of a donor stem peptide by d,d‐transpeptidases and the release of d‐Ala5. Since these enzymes generally are susceptible to penicillin and other β‐lactamases, they are also named penicillin‐binding proteins (PBP) (cf. Table ). In the presence of sub‐lethal concentrations of penicillin, strains can be selected for that contain mainly l,d‐(DAP‐DAP) crosslinks. These are formed by penicillin‐insensitive ld‐transpeptidases, which connect the d‐amino group of DAP3 of one stem peptide with the l‐carboxylic acid group of DAP3 of a second (the donor). Enzymes of the latter specificity are also required to attach the peptidoglycan to the outer membrane in Gram‐negative bacteria via Braun's lipoprotein, linking the side‐chain amino group of the protein's C‐terminal lysine with DAP in the peptidoglycan. In Gram‐positive bacteria, the peptidoglycan network is modified by long‐chain polyol‐phosphate polymers (teichoic acids) that are either covalently attached to the C6 hydroxyl groups of MurNAc through phosphodiester bonds (wall teichoic acids, WTAs) or anchored in the cytoplasmic membrane and connected to peptidoglycan via ionic interactions (lipoteichoic acids, LTAs). Thus, cell wall synthesis involves the coordinated assembly – and in turn cell wall degradation the coordinated disassembly – of a thick peptidoglycan–teichoic acid complex in Gram‐positive bacteria as well as a thin peptidoglycan layer linked to an outer membrane in Gram‐negative bacteria.

Figure 2.

Schematic structure of the peptidoglycan network of E. coli and sites of cleavage by cell wall hydrolases, targeting either the glycan (blue) or the peptide part (red) of the peptidoglycan. The boxed part of the peptidoglycan network is the same shown in Figure in more chemical detail. For members of the respective enzyme groups see Table .

Figure 3.

Cleavage of the peptidoglycan by two distinct types of muramidases. Lysozyme‐like muramidases catalyse a hydrolysis reaction yielding products that carry MurNAc at their reducing ends, whereas the lytic transglycosylases catalyse an intramolecular transglycosylation reaction yielding anhMurNAc termini. GlcNAc‐anhMurNAc‐peptides are the major cell wall turnover products of E. coli and other Gram‐negative bacteria, whereas GlcNAc‐MurNAc‐peptides presumably are generated mostly in Gram‐positive bacteria.

Figure 4.

Peptidoglycan turnover and recycling in E. coli. In red, enzymes that act on the peptide, in blue, enzymes that act on the glycan (sugar) portion of the peptidoglycan. Enzymes shown in black are involved in peptidoglycan synthesis or general catabolic pathways. For details see text.

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References

Adin DM, Engle JT, Goldman WE, McFall‐Ngai MJ and Stabb EV (2009) Mutations in ampG and lytic transglycosylase genes affect the net release of peptidoglycan monomers from Vibrio fischeri. Journal of Bacteriology 191: 2012–2022.

Amoroso A, Boudet J, Berzigotti S et al. (2012) A peptidoglycan fragment triggers β‐lactam resistance in Bacillus licheniformis. PLoS Pathogens 8: e1002571.

Artola‐Recolons C, Carrasco‐Lopez C, Llarrull LI et al. (2011) High‐resolution crystal structure of MltE, an outer membrane‐anchored endolytic peptidoglycan lytic transglycosylase from E. coli. Biochemistry 50: 2384–2386.

Atilano ML, Pereira PM, Yates J et al. (2010) Teichoic acids are temporal and spatial regulators of peptidoglycan cross‐linking in Staphylococcus aureus. Proceedings of the National Academy of Sciences of the USA 107: 18991–18996.

Atrih A, Bacher G, Allmaier G, Williamson MP and Foster SJ (1999) Analysis of peptidoglycan structure from vegetative cells of Bacillus subtilis 168 and role of PBP 5 in peptidoglycan maturation. Journal of Bacteriology 181: 3956–3966.

Atrih A, Zollner P, Allmaier G, Williamson MP and Foster SJ (1998) Peptidoglycan structural dynamics during germination of Bacillus subtilis 168 endospores. Journal of Bacteriology 180: 4603–4612.

Bacik JP, Whitworth GE, Stubbs KA et al. (2011) Molecular basis of 1,6‐anhydro bond cleavage and phosphoryl transfer by Pseudomonas aeruginosa 1,6‐anhydro‐N‐acetylmuramic acid kinase. Journal of Biological Chemistry 286: 12283–12291.

Boothby D, Daneo‐Moore L, Higgins ML, Coyette J and Shockman GD (1973) Turnover of bacterial cell wall peptidoglycans. Journal of Biological Chemistry 248: 2161–2169.

Boudreau MA, Fisher JF and Mobashery SS (2012) Messenger functions of the bacterial cell wall‐derived muropeptides. Biochemistry 51: 2974–2990.

Chaloupka J, Rihova L and Kreckova P (1964) Degradation and turnover of bacterial cell wall mucopeptides in growing bacteria. Folia Microbiologica (Praha) 24: 9–15.

Chan YA, Hackett KT and Dillard JP (2012) The lytic transglycosylases of Neisseria gonorrhoeae. Microbial Drug Resistance in press.

Chen R, Guttenplan SB, Blair KM and Kearns DB (2009) Role of the sigma D‐dependent autolysins in Bacillus subtilis population heterogeneity. Journal of Bacteriology 191: 5775–5784.

Claverys JP and Havarstein LS (2007) Cannibalism and fratricide: mechanisms and raisons d'etre. Nature Review of Microbiology 5: 219–229.

Cloud‐Hansen KA, Peterson SB, Stabb EV et al. (2006) Breaching the great wall: peptidoglycan and microbial interactions. Nature Review of Microbiology 4: 710–716.

Dubrac S, Bisicchia P, Devine KM and Msadek T (2008) A matter of life and death: cell wall homeostasis and the WalKR (YycGF) essential signal transduction pathway. Molecular Microbiology 70: 1307–1322.

Eldholm V, Johnsborg O, Haugen K, Ohnstad HS and Havarstein LS (2009) Fratricide in Streptococcus pneumoniae: contributions and role of the cell wall hydrolases CbpD, LytA and LytC. Microbiology 155: 2223–2234.

Fabret C and Hoch JA (1998) A two‐component signal transduction system essential for growth of Bacillus subtilis: implications for anti‐infective therapy. Journal of Bacteriology 180: 6375–6383.

Fukushima T, Kitajima T, Yamaguchi H et al. (2008) Identification and characterization of novel cell wall hydrolase CwlT: a two‐domain autolysin exhibiting N‐acetylmuramidase and D,L‐endopeptidase activities. Journal of Biological Chemistry 283: 11117–11125.

Goodell EW (1985) Recycling of murein by E. coli. Journal of Bacteriology 163: 305–310.

Goodell EW and Schwarz U (1985) Release of cell wall peptides into culture medium by exponentially growing E. coli. Journal of Bacteriology 162: 391–397.

Hashimoto M, Ooiwa S and Sekiguchi J (2011) Synthetic lethality of the lytE cwlO genotype in Bacillus subtilis is caused by lack of D,L‐endopeptidase activity at the lateral cell wall. Journal of Bacteriology 194: 796–803.

Hayhurst EJ, Kailas L, Hobbs JK and Foster SJ (2008) Cell wall peptidoglycan architecture in Bacillus subtilis. Proceedings of the National Academy of Sciences of the USA 105: 14603–14608.

van Heijenoort J (2011) Peptidoglycan hydrolases of E. coli. Microbiology and Molecular Biology Reviews 75: 636–663.

Höltje J‐V (1996) A hypothetical holoenzyme involved in the replication of the murein sacculus of E. coli. Microbiology 142(part 8): 1911–1918.

Höltje JV (1998) Growth of the stress‐bearing and shape‐maintaining murein sacculus of E. coli. Microbiology and Molecular Biology Reviews 62: 181–203.

Jacobs C, Huang LJ, Bartowsky E, Normark S and Park JT (1994) Bacterial cell wall recycling provides cytosolic muropeptides as effectors for β‐lactamase induction. EMBO Journal 13: 4684–4694.

Jaeger T and Mayer C (2008a) N‐acetylmuramic acid 6‐phosphate lyases (MurNAc etherases): role in cell wall metabolism, distribution, structure, and mechanism. Cellular and Molecular Life Sciences 65: 928–939.

Jaeger T and Mayer C (2008b) The transcriptional factors MurR and catabolite activator protein regulate N‐acetylmuramic acid catabolism in E. coli. Journal of Bacteriology 190: 6598–6608.

Kusser W and Fiedler F (1983) Teichoicase from Bacillus subtilis Marburg. Journal of Bacteriology 155: 302–310.

Litzinger S, Duckworth A, Nitzsche K et al. (2010a) Muropeptide rescue in Bacillus subtilis involves sequential hydrolysis by beta‐N‐acetylglucosaminidase and N‐acetylmuramyl‐L‐alanine amidase. Journal of Bacteriology 192: 3132–3143.

Litzinger S, Fischer S, Polzer P et al. (2010b) Structural and kinetic analysis of Bacillus subtilis N‐acetylglucosaminidase reveals a unique Asp‐His dyad mechanism. Journal of Biological Chemistry 285: 35675–33584.

Litzinger S and Mayer C (2010) Chapter 1: the murein sacculus. In: König H, Claus H and Varma A (eds) Prokaryotic Cell Wall Compounds – Structure and Biochemistry, pp. 3–52. Heidelberg: Springer.

Mauck J, Chan L and Glaser L (1971) Turnover of the cell wall of Gram‐positive bacteria. Journal of Biological Chemistry 246: 1820–1817.

Mesnage S, Chau F, Dubost L and Arthur M (2008) Role of N‐acetylglucosaminidase and N‐acetylmuramidase activities in Enterococcus faecalis peptidoglycan metabolism. Journal of Biological Chemistry 283: 19845–19853.

Morlot C, Uehara T, Marquis KA, Bernhardt TG and Rudner DZ (2010) A highly coordinated cell wall degradation machine governs spore morphogenesis in Bacillus subtilis. Genes & Development 24: 411–422.

Nelson DE and Young KD (2001) Contributions of PBP 5 and DD‐carboxypeptidase penicillin binding proteins to maintenance of cell shape in E. coli. Journal of Bacteriology 183: 3055–3064.

Park JT and Uehara T (2008) How bacteria consume their own exoskeletons (turnover and recycling of cell wall peptidoglycan). Microbiological and Molecular Biology Reviews 72: 211–227.

Pfeiffer JM, Moynihan PJ, Clarke CA, Vandenende A and Clarke AJ (2012) Control of lytic transglycosylase activity within bacterial cell walls. In: Reid CW, Twine SM and Reith AN (eds) Bacterial Glycomics. Norfolk, UK: Caister Academic press.

Popham DL and Young KD (2003) Role of penicillin‐binding proteins in bacterial cell morphogenesis. Current Opinion in Microbiology 6: 594–599.

Popowska M (2004) Analysis of the peptidoglycan hydrolases of Listeria monocytogenes: multiple enzymes with multiple functions. Polish Journal of Microbiology 53: suppl. 29–34.

Priyadarshini R, Popham DL and Young KD (2006) Daughter cell separation by penicillin‐binding proteins and peptidoglycan amidases in E. coli. Journal of Bacteriology 188: 5345–5355.

Reith J and Mayer C (2011a) Characterization of a glucosamine/glucosaminide N‐acetyltransferase of Clostridium acetobutylicum. Journal of Bacteriology 193: 5393–5399.

Reith J and Mayer C (2011b) Peptidoglycan turnover and recycling in Gram‐positive bacteria. Applied Microbiology and Biotechnology 92: 1–11.

Romeis T, Vollmer W and Höltje JV (1993) Characterization of three different lytic transglycosylases in E. coli. FEMS Microbiology Letters 111: 141–146.

Scheurwater EM and Burrows LL (2011) Maintaining network security: how macromolecular structures cross the peptidoglycan layer. FEMS Microbiology Letters 318: 1–9.

Schirner K, Marles‐Wright J, Lewis RJ and Errington J (2009) Distinct and essential morphogenic functions for wall‐ and lipo‐teichoic acids in Bacillus subtilis. EMBO Journal 28: 830–842.

Shah IM and Dworkin J (2010) Induction and regulation of a secreted peptidoglycan hydrolase by a membrane Ser/Thr kinase that detects muropeptides. Molecular Microbiology 75: 1232–1243.

Shah IM, Laaberki MH, Popham DL and Dworkin J (2008) A eukaryotic‐like Ser/Thr kinase signals bacteria to exit dormancy in response to peptidoglycan fragments. Cell 135: 486–496.

Smith TJ, Blackman SA and Foster SJ (2000) Autolysins of Bacillus subtilis: multiple enzymes with multiple functions. Microbiology 146(Pt 2): 249–262.

Stapleton MR, Horsburgh MJ, Hayhurst EJ et al. (2007) Characterization of IsaA and SceD, two putative lytic transglycosylases of Staphylococcus aureus. Journal of Bacteriology 189: 7316–7325.

Sudiarta IP, Fukushima T and Sekiguchi J (2010) Bacillus subtilis CwlQ (previous YjbJ) is a bifunctional enzyme exhibiting muramidase and soluble‐lytic transglycosylase activities. Biochemical and Biophysical Research Communications 398: 606–612.

Suvorov M, Lee M, Hesek D, Boggess B and Mobashery S (2008) Lytic transglycosylase MltB of E. coli and its role in recycling of peptidoglycan strands of bacterial cell wall. Journal of American Chemical Society 130: 11878–11879.

Templin MF, Ursinus A and Höltje JV (1999) A defect in cell wall recycling triggers autolysis during the stationary growth phase of E. coli. EMBO Journal 18: 4108–4117.

Thunnissen AM, Rozeboom HJ, Kalk KH and Dijkstra BW (1995) Structure of the 70‐kDa soluble lytic transglycosylase complexed with bulgecin A. Implications for the enzymatic mechanism. Biochemistry 34: 12729–12737.

Typas A, Banzhaf M, Gross CA and Vollmer W (2012) From the regulation of peptidoglycan synthesis to bacterial growth and morphology. Nature Review of Microbiology 10: 123–136.

Uehara T and Park JT (2008a) Growth of E. coli: significance of peptidoglycan degradation during elongation and septation. Journal of Bacteriology 190: 3914–3922.

Uehara T and Park JT (2008b) Peptidoglycan recycling EcoSal‐Eschericia coli and Salmonella. In: Cellular and Molecular Biology, 3rd edn, Washington, DC: ASM Press, posted on October 15, 2008.

Uehara T, Suefuji K, Jaeger T, Mayer C and Park JT (2006) MurQ etherase is required by E. coli in order to metabolize anhydro‐N‐acetylmuramic acid obtained either from the environment or from its own cell wall. Journal of Bacteriology 188: 1660–1662.

Vollmer W, Joris B, Charlier P and Foster S (2008) Bacterial peptidoglycan (murein) hydrolases. FEMS Microbiology Review 32: 259–286.

Weidenmeier C and Peschel A (2008) Teichoic acids and releated cell‐wall glycopolymers in Gram‐positive physiology and host interactions. Nature Microbiology Review 6: 276–287.

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Mayer, Christoph(Jul 2012) Bacterial Cell Wall Recycling. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021974]