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Peptidoglycan

  1. Kevin D Young

Published Online: 17 OCT 2011

DOI: 10.1002/9780470015902.a0000702.pub2

eLS

eLS

How to Cite

Young, K. D. 2011. Peptidoglycan. eLS. .

Author Information

  1. University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA

Publication History

  1. Published Online: 17 OCT 2011

Abstract

Peptidoglycan is the rigid, but flexible, macromolecule that surrounds and protects individual bacterial cells. It supplies the foundation for bacterial cell walls, defines an organism's shape and anchors protein complexes and extracellular organelles to the cell surface, all while remaining porous enough to admit essential nutrients and large compounds. Peptidoglycan fragments trigger neighbouring microorganisms to grow or to modify their own walls, serve as maturation signals for vertebrate immune systems and may be used to manipulate the immune system for the benefit of pathogenic organisms. Because it is unique to bacteria, peptidoglycan is one of the most valuable targets to which antibiotics may be directed. Although the components of peptidoglycan are known and we have a basic understanding of its biosynthesis, there remains a great deal to learn about its three-dimensional organisation, its biological properties and activities, and how it expands and divides during bacterial growth.

Key Concepts:

  • Peptidoglycan is the basic component of the bacterial cell wall, which is the protective structure that surrounds and protects most bacteria.

  • Peptidoglycan is composed of numerous glycan (sugar-based) polymers that are covalently crosslinked to one another by short peptide side-chains, creating a single bag-like macromolecule called the sacculus.

  • Penicillin-binding proteins are responsible for the final stages of peptidoglycan synthesis, but additional proteins modify peptidoglycan in numerous ways in different bacteria.

  • Because of its complexity, the exact three-dimensional structure of peptidoglycan is not known, but it is thought to look like a net with pores 2–5 nm in diameter.

  • Large protein complexes and organelles are embedded in or are threaded through peptidoglycan, indicating that enzymes must degrade peptidoglycan in a limited way to create holes in which these structures may be assembled.

  • Bacteria can change the composition and perhaps the structure of their peptidoglycan, depending on growth conditions and in response to their environmental surroundings.

  • Peptidoglycan is constantly being broken down, recycled and renewed as bacteria grow and divide.

  • Bacteria use peptidoglycan fragments to signal or manipulate other microorganisms or even human and animal immune systems.

  • Because peptidoglycan is unique to bacteria, the enzymes that synthesise it are some of the most important targets for antibiotic therapy.

Keywords:

  • bacterial cell wall;
  • murein;
  • muropeptides;
  • penicillin;
  • penicillin-binding proteins;
  • secretion;
  • cell wall recycling