Oral Presentation Lorne Infection and Immunity 2020

Understanding and preventing pathogenic bacteria from colonising host surfaces (#5)

Jason Paxman 1 , Alvin Lo 2 , Martina Jones 3 , Jeff Hou 3 , Tony Wang 1 , Lilian Hor 1 , Santosh Panjikar 4 , Mark Schembri 5 , Begoña Heras 1
  1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
  2. Division of Infection and Immunity, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia
  3. Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, QLD, Australia
  4. Macromolecular Crystallography, Australian Synchrotron, Clayton, VIC, Australia
  5. Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia

Introduction:

Bacteria utilise a wide variety of surface adhesins to interact with and colonise host surfaces and other materials, which are a critical step in bacterial infections along with the contamination of food and medical devices. Similarly adhesins are also responsible for the formation of persistent biofilms, a leading cause of bacterial resistance to antibiotics and chronic infections. The largest group of these adhesins are the non-fimbrial autotransporter adhesins, whereby until our research almost nothing was known about their structures and molecular mechanisms of action.

Aims:

We sought to uncover the structures, mode of action, regulation and roles in bacterial pathogenesis of autotransporter adhesins, and then to use this information to develop antibody based inhibitors against these virulence factors.

Methodology:

We combined a multidisciplinary approach of X-ray crystallography with biophysical, biochemical, cellular and microbiology methods.

Results:

Our 8 new crystal structures of the autotransporter adhesins show that these proteins form long >500 residue β-helices that incorporate different features to allow binding to their targets.  So far we have found these adhesins fall into 2 mechanistic groups (i) those such as UpaB from Uropathogenic E. coli that through structural modifications directly bind host surfaces1 and (ii) those such as Antigen 43 from widespread pathogenic E. coli strains that promote bacterial biofilm formation by self-interactions between neighbouring bacteria2. Remarkably, our new research shows that some adhesins such as Entertoxigenic E. coli TibA, can actually switch between these functions by novel post-translational modifications. 

Conclusions:

We are now finally uncovering for the first time the roles, mechanisms and structures of this large and uncharacterised group of bacterial proteins.  We can now appreciate in molecular detail how these adhesins interact to promote colonisation and biofilm formation. Importantly, we have used these findings to develop and patent an antibody based inhibitor that prevents biofilm formation3.

  1. [1] Paxman JJ, Lo A, Sullivan MJ, Panjikar S, Kuiper M, Whitten AE, Wang G, Luan CH, Moriel DG, Tan L, Peters KM, Gee C, Ulett GC, Schembri MA and Heras B. (2019). Unique structural features of a bacterial autotransporter adhesin suggest mechanisms for interaction with host macromolecules. Nat. Commun. 2019 Apr 29;10(1):1967
  2. [2] Heras B, Totsika M, Peters KM, Paxman JJ, Gee CL, Jarrott RJ, Perugini MA, Whitten AE and Schembri MA (2014) The antigen 43 structure reveals a molecular Velcro-like mechanism of autotransporter-mediated bacterial clumping. Proc Natl Acad Sci USA 111, 457-462.
  3. [3] Heras B, Paxman J.J. Schembri M, Lo A, Jones M, & Hou J. (2018) Australian Government Patent, Compositions and methods for reducing bacterial aggregation 2018903096.