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A semi high-throughput method for real-time monitoring of curli producing Salmonella biofilms on air-solid interfaces

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  • Ferdinand X. Choong, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Smilla Huzell, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Ming Rosenberg, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Johannes A. Eckert, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Madhu Nagaraj
  • ,
  • Tianqi Zhang, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Keira Melican, Karolinska Institutet, Royal Institute of Technology
  • ,
  • Daniel E. Otzen
  • Agneta Richter-Dahlfors, Karolinska Institutet, Royal Institute of Technology

Biofilms enable bacteria to colonize numerous ecological niches. Bacteria within a biofilm are protected by the extracellular matrix (ECM), of which the fibril-forming amyloid protein curli and polysaccharide cellulose are major components in members of Salmonella, Eschericha and Mycobacterium genus. A shortage of real-time detection methods has limited our understanding of how ECM production contributes to biofilm formation and pathogenicity. Here we present optotracing as a new semi-high throughput method for dynamic monitoring of Salmonella biofilm growth on air-solid interfaces. We show how an optotracer with binding-induced fluorescence acts as a dynamic fluorescent reporter of curli expression during biofilm formation on agar. Using spectrophotometry and microscopic imaging of fluorescence, we analyse in real-time the development of the curli architecture in relation to bacterial cells. With exceptional spatial and temporal precision, this revealed a well-structured, non-uniform distribution of curli organised in distally projecting radial channel patterns. Dynamic monitoring of the biofilm also showed defined regions undergoing different growth phases. ECM structures were found to assemble in regions of late exponential growth phase, suggesting that ECM forms on site after bacteria colonize the surface. As the optotracer biofilm method expedites screening of curli production, providing exceptional spatial-temporal understanding of the surface-associated biofilm lifestyle, this method adds a new technique to further our understanding of bacterial biofilms.

Original languageEnglish
Article number100060
Publication statusPublished - Dec 2021

Bibliographical note

Publisher Copyright:
© 2021 The Authors

    Research areas

  • Biofilm, Curli, Morphotyping, Optotracing, Real-time monitoring, Salmonella

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