The structure and function of TasA in the Bacillus subtilis biofilm matrix

Abstract

Biofilms are communities of microorganisms attached to a surface and encompassed within a self-produced extracellular matrix. The matrix functions to shield the interior cells from biotic and abiotic stresses and to retain nutrients and signalling molecules. The multiple functions of the biofilm matrix are mediated by the constituent parts which may include a combination of complex polysaccharides, lipids, nucleic acids and proteins. Some of the proteins found within the matrix are polymeric, with examples including the flagellum, pilus and amyloid-fibres. There is a growing list of proteins in the matrix that are categorised as “amyloid-like”, including the Enterobacteriacae Curli, Staphylococcus aureus Bap, Pseudomonas Fap and Bacillus subtilis TasA protein fibres that give structure to the respective biofilms. However, the categorisation of ‘amyloid-like’ to fibre-forming proteins of the biofilm matrix requires careful consideration. This thesis presents evidence that the B. subtilis TasA fibres are not amyloid in form. Through the comparison of the biochemistry and structure of a functional TasA fibre to the canonical amyloid fibre, we propose a linear assembly of TasA monomers within the fibre. The ongoing collaboration of molecular microbiology at the University of Dundee and protein biophysics at the University of Edinburgh throughout this project has also led to the discovery and characterisation of TasA surface activity and preliminary investigations of the molecular mechanism imparting surface activity are also presented.

Date of Award	2019
Original language	English
Awarding Institution	University of Dundee
Supervisor	Nicola Stanley-Wall (Supervisor)