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Curli fibers mediate internalization of Escherichia coli by eukaryotic cells
U Gophna1, M Barlev, R Seijffers
1Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel.
Abstract:
Curli fibers are adhesive surface fibers expressed by Escherichia coli and Salmonella enterica that bind several host extracellular matrix and contact phase proteins and were assumed to have a role in pathogenesis. The results presented here suggest that one such role is internalization into host cells. An E. coli K-12 strain transformed with a low-copy vector containing the gene cluster encoding curli fibers (csg operon) was internalized by several lines of eukaryotic cells. The internalization could be correlated with a high level of curli fiber expression and was abolished by disruption of the csg operon. The ability to be internalized by eukaryotic cells could be conferred even by the curli fiber gene cluster of a noninvasive K-12 strain, but the homologous csg cluster from a virulent septicemic E. coli isolate mediated a higher level of internalization. The finding that curli fibers promote bacterial internalization indicates a new role for curli fibers in pathogenesis.
Insights
Curli fibers, surface proteins of Escherichia coli and Salmonella enterica, promote bacterial entry into host cells. This discovery reveals a new mechanism by which these bacteria can cause disease.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Cell Biology
Background:
- Curli fibers are adhesive surface proteins produced by Escherichia coli and Salmonella enterica.
- These fibers bind host extracellular matrix and contact phase proteins, suggesting a role in pathogenesis.
Purpose of the Study:
- To investigate the role of curli fibers in the interaction between bacteria and host cells.
- To determine if curli fibers mediate the internalization of bacteria into eukaryotic cells.
Main Methods:
- Transformed an E. coli K-12 strain with the csg operon for curli fiber production.
- Exposed the transformed E. coli to various eukaryotic cell lines.
- Analyzed bacterial internalization levels based on curli fiber expression and gene operon disruption.
Main Results:
- E. coli expressing curli fibers were internalized by eukaryotic cells.
- Internalization correlated with high curli fiber expression and was abolished by csg operon disruption.
- The csg operon from a virulent E. coli strain mediated higher internalization levels.
Conclusions:
- Curli fibers play a significant role in promoting bacterial internalization into host cells.
- This internalization mechanism represents a novel aspect of curli-mediated pathogenesis.
- Curli fibers contribute to the infectious potential of E. coli and Salmonella.