Analysis of peptidoglycan architecture in Gram positive bacteria

Lead Research Organisation: University of Sheffield
Department Name: Molecular Biology and Biotechnology


The outer cell wall of bacteria is essential to hold the cells together and gives them their characteristic shapes. Peptidoglycan is the structural material responsible for maintaining cellular integrity for most bacteria and its synthesis is the site of action of some of the most important antibiotics (such as penicillin). Peptidoglycan is made of strands of sugars linked together by strings of amino acids. The structure of peptidoglycan is dynamic to allow for cell growth, division and many other features. Surprisingly we do not know how the chemical structure of the peptidoglycan leads to its final architecture, which of course is necessary for its essential functions. The project will take an integrated approach to determine the length of the sugar strands in the peptidoglycan and how this is involved in the ability of the polymer to maintain its role. The project will address a fundamental area of microbiology.

Technical Summary

Bacterial cell wall peptidoglycan is essential for the maintenance of cellular viability and shape determination for most eubacteria. Peptidoglycan is a polymer of glycan strands cross-linked via peptide sidechains. It is a dynamic structure being synthesised, modified and hydrolysed to allow for cell growth, division and many other important cellular features. Even though we understand a lot about the chemical structure of peptidoglycan, how this translates to the final architecture (and thus its stress bearing properties) is largely unknown. Recently measurement of the crucial glycan strand length parameter (in Staphylococcus aureus and Escherichia coli) has suggested very short chains (mostly <30 disaccharides). However our results from B. subtilis have surprisingly revealed a wide range of strand lengths including some very long indeed (>500 disaccharides). The project will analyse the role of glycan strand length and its dynamics in B. subtilis, S. aureus and other Gram positive organisms. A range of complementary approaches will determine how peptidoglycan structural parameters lead to the architecture, which is responsible for cellular morphology and integrity.


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Description 1. Determination of glycan strand length in Bacillus subtilis peptidoglycan: Our biochemical studies revealed that the glycan strands could not be resolved by conventional HPLC analysis. A novel AFM approach was developed to visualize them for the first time. This showed glycan of up to 5 microns (twice the length of the cell).
2. Use of Atomic Force Microscopy to determine the architecture of the peptidoglycan of B. subtilis: The above chain length analysis alluded to a complex peptidoglycan architecture. Using AFM and isolated peptidoglycan sacculi we were for the first time able to show the architecture of this essential polymer. This revealed a totally novel and unexpected architecture, overturning the textbook, and all previous, models of the architecture of this polymer.
3. Development of a new model for peptidoglycan architecture: A new model based on our results was developed and published (Hayhurst et al. (2008) PNAS 105, 14603-14608).
Exploitation Route Action of antibiotics
Sectors Pharmaceuticals and Medical Biotechnology

Description Bacterial cell wall architecture and dynamics
Amount £503,877 (GBP)
Funding ID BB/H011005/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 03/2010 
End 03/2014