Abstract
The bacterial cell wall is a multicomponent structure that provides structural support and protection. In monoderm species, the cell wall is made up predominantly of peptidoglycan, teichoic acids and capsular glycans. Filamentous monoderm Actinobacteria incorporate new cell-wall material at their tips. Here we use cryo-electron tomography to reveal the architecture of the actinobacterial cell wall of Streptomyces coelicolor. Our data shows a density difference between the apex and subapical regions. Removal of teichoic acids results in a patchy cell wall and distinct lamellae. Knock-down of tagO expression using CRISPR-dCas9 interference leads to growth retardation, presumably because build-in of teichoic acids had become rate-limiting. Absence of extracellular glycans produced by MatAB and CslA proteins results in a thinner wall lacking lamellae and patches. We propose that the Streptomyces cell wall is composed of layers of peptidoglycan and extracellular polymers that are structurally supported by teichoic acids.
Highlights
The bacterial cell wall is a multicomponent structure that provides structural support and protection
Tomograms of some of the sacculi displayed extensive folding perpendicular to the long axis of the hyphae. These folds are similar in orientation compared to the shears and tears previously observed in sacculi preps of B. subtilis[43], likewise supporting a circumferential orientation of the glycan strands in the cell wall (Supplementary Fig. 1)[43]
In this work, we show that the cell envelope of the polar growing bacterium S. coelicolor is a complex structure composed of PG and extracellular glycans that are structurally linked by teichoic acids
Summary
The bacterial cell wall is a multicomponent structure that provides structural support and protection. In many unicellular rod-shaped bacteria, such as in the model organisms Escherichia coli and Bacillus subtilis, the cell wall expands by the incorporation of new PG along the length of the cell[12,13] This lateral elongation is guided by highly curved MreB filaments along the cell circumference[14,15,16,17]. The inner lamella is composed of PG, and the glycans produced by the CslA and MatAB proteins form a discrete outer lamella, which is tethered to the inner layer via teichoic acids. These findings warrant a revised model for the cell-wall architecture in a polar growing bacterium
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