Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Bacterial colonisation and biofilms, how adhesins work at the molecular level - and how to block them (#117)

Jason J Paxman 1 , Alvin Lo 2 , Lilian Hor 1 , Santosh Panjikar 3 , Tony Wang 1 , Matthew J Sullivan 4 , Michael Kuiper 5 , Glen C Ulett 4 , Mark Schembri 2 , Begoña Heras 1
  1. Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
  2. Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
  3. Macromolecular Crystallography, Australian Synchrotron, Clayton, VIC, Australia
  4. School of Medical Science and Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
  5. Molecular & Materials Modelling group Data61, CSIRO, Docklands, Melbourne, VIC, 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 inhibitors against these virulence factors.

Methodology:

We combined a multidisciplinary approach of using 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 novel structural modifications forms two distinct host binding sites to directly adhere to 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 for the first time that the function of some adhesins such as entertoxigenic E. coli TibA, can be switched post-translationally by a novel form glycosylation. 

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 Australia's first inhibitor that targets medical biofilms3.

  1. Paxman JJ, et al., (2019) Unique structural features reveal the dual binding mechanism of an autotransporter adhesion, Nat Commun 10(1):1967.
  2. Heras B, ..Paxman JJ, et al., (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. Heras B, Paxman J.J. et al., (2019) Compositions and methods for reducing bacterial aggregation, International Patent (PCT/AU2019/050893).