Bacteria at Surfaces

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Fig. 1. Biofilm life cycle.
The Bacteria at Surfaces group focuses on understanding, predicting and controlling material-bacteria interactions for health-related applications. Especially, we combine interdisciplinary knowledge in the pursuit of understanding how bacteria adhere to surfaces, and how the adhesion can be controlled. Among our core strengths are the broad expertise, ranging from microbiology to biomaterials, and the long-term experience in working with industry and finding solutions to biofilm problems.

 

The key research aspects of the Bacteria at Surfaces group include:

  • Studying basic mechanisms in bacterial adhesion and biofilm formation

  • Developing antibacterial and anti-adhesive surfaces to prevent/reduce biofilm formation

  • Designing new approaches to prevent/treat biofilm infections
     

Predictive in vitro biofilm models

Many models have been developed to study biofilms including simple in vitro and complex in vivo ones. Even though these models have progressively provided knowledge and information on biofilm formation, we are still far from a complete understanding on how various factors influence the interactions between the biofilms and the medical devices. The Bacteria at Surfaces group is interested in the development and improvement of clinically relevant in vitro biofilm models under specific in vivo conditions such as flow rate, nutrient content, mixed biofilm, and co-existence of human and bacterial cells, aiming for more reliable assessment of antimicrobial surfaces.

Interaction of bacterial cells and surfaces

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Fig. 2. Scanning electron microscopy (SEM) image of a ureteral stent surface covered with a dense mass of crystalline biofilm.
Upon sensing and interacting with surfaces, bacteria trigger a variety of changes in gene expression, including the genes essential for cell-cell communication, motility and surface attachment. Although changes in these phenotypes have been observed, the mechanisms used by bacterial cells for sensing and responding to surfaces are still not well understood. To develop novel classes of materials that inhibit or reduce bacterial adhesion or proliferation, a better understanding of these mechanisms is necessary. The Bacteria at Surfaces group is interested in studying the underlining mechanisms of surface sensing at the molecular level and the consequent impact on cell adhesion.

 

Bacterial strains and methods for studying bacteria-surface interactions

The Bacteria at Surfaces group works with different bacterial strains such as Gram negative and Gram positive species, multi-resistant pathogens, biosafety level I and II bacterial species.

We study biofilms in microtiter plates, flow chambers, as well as in bioreactor systems under static or dynamic conditions. Bacterial adhesion and biofilms on surfaces are analyzed by different methods such as Crystal violet assays, Fluorescence assays, Microscopy (CLSM, SEM), Real-time quantitative PCR.

 

Selected collaboration projects
  • Collaboration with Hospital St. Gallen (2015-2016): Biofilms on ureteral stents - Development of an in vitro simulation model towards exploring novel stent surfaces and materials
  • CTI project (2015-2017): Metal-ion doped TiN layers to reduce hospital acquired infections
  • CTI project (2014-2016): Endodontic cleaning and disinfection solution
  • CTI project (2014-2016): Development of novel non-biocidal textile coatings reducing sweat odor accumulation
  • CTI project (2014-2015): Biofilm removal from and effective cleaning of medical devices by means of innovative enzymatic detergents
  • CTI project (2011-2013): Development of novel non-biocidal textile coatings reducing bacterial adhesion