\textit{Helicobacter pylori} displays spiral trajectories while swimming like a cork-screw in solutions.

\textit{Helicobacter pylori} is a helical shaped bacterium that causes gastritis, ulcers and gastric cancer in humans and other animals. In order to colonize the harsh acidic environment of the stomach \textit{H. pylori} has evolved a unique biochemical mechanism to go across the viscoelastic gel-like gastric mucus layer. Many studies have been conducted on the swimming of \textit{H. pylori} in viscous media. However a yet unanswered question is if the helical cell shape influences bacterial swimming dynamics or confers any advantage when swimming in viscous solution. We will present measurements of \textit{H. pylori} trajectories displaying corkscrew motion while swimming in solution obtained by tracking single cells using 2-dimensional phase contrast imaging at high magnification and fast frame rates and simultaneously imaging their shape. We observe a linear relationship between swimming speed and rotation rate. The experimental trajectories show good agreement with trajectories calculated using a regularized Stokeslet method to model the low Reynolds number swimming behavior.