Microrheology of Mucin: Tracking Particles and Helicobacter Pylori Bacteria

The gastric ulcer and cancer causing bacteria, Helicobacter Pylori have uniquely adapted to swim across the viscoelastic mucus gel that lines the stomach epithelial surface and colonize in the harsh acidic environment of the stomach. In this paper we first briefly review results of bacteria tracking and oscillatory shear rheology studies to suggest how the bacteria get across the viscoelastic mucus gel by using a chemical mechanism to raise the pH from acidic to neutral which also triggers a gel to sol transition of mucin. We then present new microrheology studies to show that the bacterium influences the Brownian motion of spherical tracer particles in culture broth solution and in solutions of gastric mucin. The elastic and viscous moduli obtained by tracking particles in the mucin solutions are found to decrease in the presence of bacteria. We also examined the Brownian motion of the bacteria themselves and find that motile bacteria display super-diffusive anomalous Brownian motion while the immotile bacteria exhibit regular diffusive Brownian motion.