Different walls for rods and balls: the diversity of peptidoglycan

Peptidoglycan performs the essential role of resisting turgor in the cell walls of most bacteria. It determines cell shape, and its biosynthesis is the target for many important antibiotics. The fundamental chemical building blocks of peptidoglycan are conserved: repeating disaccharides cross-linked by peptides. However, these blocks come in many varieties and can be assembled in different ways. So beyond the fundamental similarity, prodigious chemical, organizational and architectural diversity is revealed. Here, we track the evolution of our current understanding of peptidoglycan and underpinning technical and methodological developments. The origin and function of chemical diversity is discussed with respect to some well-studied example species. We then explore how this chemistry is manifested in elegant and complex peptidoglycan organization and how this is interpreted in different and sometimes controversial architectural models. We contend that emerging technology brings about the possibility of achieving a complete understanding of peptidoglycan chemistry, through architecture, to the way in which diverse species and populations of cells meet the challenges of maintaining viability and growth within their environmental niches, by exploiting the bioengineering versatility of peptidoglycan.

Peptidoglycan architecture in B. subtilis, S. aureus and E. coli.

A. Metrics of peptidoglycan for comparison. Ranges are lowest and highest values identified in the literature (Vollmer and Seligman, 2010; Wheeler et al., 2011). In S. aureus and E. coli these are average values, in B. subtilis they are a representative of the overall range.

B. AFM gallery of sacculi comprising images comprising multiple sacculi per field, and key architectural details specific to each species (Hayhurst et al., 2008; Turner et al., 2010; 2013).

C. Interpretive diagrams drawn from yellow rectangles marked in ‘B’.

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