Formation of functional, non-amyloidogenic fibres by recombinant Bacillus subtilis TasA.

Elliot Erskine,Louise C Serpell,Tetyana Sukhodub,Chris Earl,Rachel M C Gillespie,Nicola R Stanley‐Wall,Cait E Macphee,Marieke Schor,Keith M Bromley,Lauren Clark,Paul K Fyfe,Ryan J Morris

doi:10.1111/mmi.13985

Elliot Erskine, Louise C Serpell + Show 10 more

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https://doi.org/10.1111/mmi.13985

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Abstract

SummaryBacterial biofilms are communities of microbial cells encased within a self‐produced polymeric matrix. In the Bacillus subtilis biofilm matrix, the extracellular fibres of TasA are essential. Here, a recombinant expression system allows interrogation of TasA, revealing that monomeric and fibre forms of TasA have identical secondary structure, suggesting that fibrous TasA is a linear assembly of globular units. Recombinant TasA fibres form spontaneously, and share the biological activity of TasA fibres extracted from B. subtilis, whereas a TasA variant restricted to a monomeric form is inactive and subjected to extracellular proteolysis. The biophysical properties of both native and recombinant TasA fibres indicate that they are not functional amyloid‐like fibres. A gel formed by TasA fibres can recover after physical shear force, suggesting that the biofilm matrix is not static and that these properties may enable B. subtilis to remodel its local environment in response to external cues. Using recombinant fibres formed by TasA orthologues we uncover species variability in the ability of heterologous fibres to cross‐complement the B. subtilis tasA deletion. These findings are indicative of specificity in the biophysical requirements of the TasA fibres across different species and/or reflect the precise molecular interactions needed for biofilm matrix assembly.

Highlights

Biofilms are communities of microbial cells that underpin diverse processes including sewage bioremediation, plant growth promotion, chronic infections and industrial biofouling (Costerton et al, 1987)
Bacterial biofilms are communities of microbial cells encased within a self-produced polymeric matrix
A recombinant expression system allows interrogation of TasA, revealing that monomeric and fibre forms of TasA have identical secondary structure, suggesting that fibrous TasA is a linear assembly of globular units

Summary

Introduction

Biofilms are communities of microbial cells that underpin diverse processes including sewage bioremediation, plant growth promotion, chronic infections and industrial biofouling (Costerton et al, 1987). The microbial cells resident in the biofilm are encased within a self-produced extracellular polymeric matrix that commonly comprises lipids, proteins, extracellular DNA and exopolysaccharides (Flemming and Wingender, 2010; Hobley et al, 2015). This matrix fulfils a variety of functions for the community, from providing structural rigidity and protection from the external environment, to supporting signal transduction and nutrient adsorption (Flemming and Wingender, 2010; Dragoš and Kovács, 2017; Vidakovic et al, 2018). The second component is the protein BslA that is responsible for the non-wetting nature of the biofilm (Kobayashi and Iwano 2012; Hobley et al, 2013; Bromley et al, 2015) and for biofilm architecture, independently of its

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Conclusion