The Influence of Morphology on the Swimming Behavior of Helicobacter Pylori

Speaker: Joseph Hardcastle

When: April 30, 2015 (Thu), 11:00AM to 12:00PM (add to my calendar)
Location: PRB 365

This event is part of the Departmental Seminars.

Dissertation Committee: Rama Bansil, Steve Ahlen, Shyamsunder Erramilli, Kirill Korolev, Pankaj Mehta

Abstract:

Bacterial motility plays a key role in a bacterium’s ability to successful colonize a host environment. However, the role of cell morphology and its link to motility is not well understood. Helicobacter Pylori, the bacterium that causes stomach ulcers and cancer, is a prime example of this. This bacterium has a helical cell shape that has long been believed to provide an advantage in penetrating the viscous mucus layer protecting the stomach lining, its niche environment. To explore this we have performed live cell bacteria tracking using optical microscopy of helical cells and mutants that have a straight rod shape. Analysis of bacterial swimming trajectories indicates that H. Pylori uses a run-reverse swimming behavior, with bacteria swimming in straight trajectories, runs, interrupted by reversals events, during which they reverse their swimming direction by ~180o. This run-reverse behavior when bacteria swim in mucin solutions, with reversals decreasing and stops increasing. Comparing the swimming of bacteria with different cell shapes shows shape plays little role in altering swimming behavior, but can result in increased swimming speeds. To obtain further insight we modeled bacterial swimming using several different hydrodynamic models. Experimental and modeling results agree that a helical cell shape can increase swimming speeds by ~10% depending on cell body parameters. Lastly, we explore how changing the number of flagella impacts swimming speed. We find that modulating flagella number results in larger changes in swimming speed than altering cell shape, with increasing number of flagella resulting in increasing swimming speeds. Taken together our results show that the helical cell shape of H. Pylori does play a role in bacterial swimming, however compared to other factors, such as flagella number, this effect seems to be small. This poses an interesting question as to whether cell shape may play another role in bacterial colonization which is yet unknown.

Hardcastle