The role of the liquid crystalline state in the bundling of Salmonella enterica serovar Typhimurium flagella

Abstract

Salmonella bacteria owe their motility to the rotation of bundled protein filaments known as flagella. While the method by which flagella impart motility is known, there is a scarcity of data elucidating the critical process of flagellum bundling itself. This work hypothesises the process of flagellum bundling to be an energetically driven phenomenon in which a physical state transition drives the formation of the flagellum bundle at the surface of a Salmonella cell. In vitro analysis of intact flagella, detached and purified from Salmonella enterica serovar Typhimurium cells, with cross-polarised light microscopy demonstrates a transition from an isotropic to mesophasic suspension at physiologically relevant concentrations. We believe the state transition of flagellum suspensions to the liquid crystalline state directs the formation of the flagellum bundle and thus plays a role in Salmonella motility that, until this point, has been sparsely investigated.

Keywords:

• flagella
• liquid crystal
• motility
• Salmonella
• flagellum bundle

Acknowledgements

The authors acknowledge Zvonimir Dogic of Brandeis University and Keiichi Namba of Osaka University for generously providing S. enterica serovar Typhimurium strains SJW1103, SJW1655 and SJW2869. We would also like to thank Oleg Lavrentovich for critical review of this manuscript and the Miami University Center for Advanced Microscopy and Imaging.

Funding

This work was supported by the Kent State Graduate Student Senate under a research grant and the National Science Foundation [NSF DMR0645461], both awarded to SEF.