Abstract
Many bacteria in nature exist in multicellular communities termed biofilms, where cells are embedded in an extracellular matrix that provides rigidity to the biofilm and protects cells from chemical and mechanical stresses. In the Gram-positive model bacterium Bacillus subtilis, TasA is the major protein component of the biofilm matrix, where it has been reported to form functional amyloid fibres contributing to biofilm structure and stability. Here, we present electron cryomicroscopy structures of TasA fibres, which show that, rather than forming amyloid fibrils, TasA monomers assemble into fibres through donor-strand exchange, with each subunit donating a β-strand to complete the fold of the next subunit along the fibre. Combining electron cryotomography, atomic force microscopy, and mutational studies, we show how TasA fibres congregate in three dimensions to form abundant fibre bundles that are essential for B. subtilis biofilm formation. Our study explains the previously observed biochemical properties of TasA and shows how a bacterial extracellular globular protein can assemble from monomers into β-sheet-rich fibres, and how such fibres assemble into bundles in biofilms.
| Original language | American English |
|---|---|
| Article number | 7082 |
| Journal | Nature Communications |
| Volume | 13 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2022 |
Bibliographical note
Funding Information:The authors would like to thank Sjors Scheres and Jan Löwe for helpful discussions and are grateful to Sigal Ben-Yehuda and to Bing Zhou for insightful discussions and for their generous help with strain construction. We are thankful for technical support by Shraddha Nayak at the Visual Aids department of the MRC Laboratory of Molecular Biology. L.C. and M.G. are grateful to Tsafi Danieli and Noa Dekel for fruitful discussions. T.A.M.B. is a recipient of a Sir Henry Dale Fellowship, jointly funded by the Wellcome Trust and the Royal Society (202231/Z/16/Z). T.A.M.B. would like to thank the Vallee Research Foundation, the Leverhulme Trust and the Lister Institute of Preventative Medicine for support. J.B. is supported by a Medical Research Council graduate studentship (grant numbers MR/K501256/1 and MR/N013468/1). M.G. acknowledges the support of the Neubauer Foundation for the PhD fellowship. L.C. and T.A.M.B. thank the support of the HUJI-UK-Spine joint seed funding.
Funding Information:
The authors would like to thank Sjors Scheres and Jan Löwe for helpful discussions and are grateful to Sigal Ben-Yehuda and to Bing Zhou for insightful discussions and for their generous help with strain construction. We are thankful for technical support by Shraddha Nayak at the Visual Aids department of the MRC Laboratory of Molecular Biology. L.C. and M.G. are grateful to Tsafi Danieli and Noa Dekel for fruitful discussions. T.A.M.B. is a recipient of a Sir Henry Dale Fellowship, jointly funded by the Wellcome Trust and the Royal Society (202231/Z/16/Z). T.A.M.B. would like to thank the Vallee Research Foundation, the Leverhulme Trust and the Lister Institute of Preventative Medicine for support. J.B. is supported by a Medical Research Council graduate studentship (grant numbers MR/K501256/1 and MR/N013468/1). M.G. acknowledges the support of the Neubauer Foundation for the PhD fellowship. L.C. and T.A.M.B. thank the support of the HUJI-UK-Spine joint seed funding.
Publisher Copyright:
© 2022, The Author(s).