Mucin is the major glycoprotein that is responsible for the viscoelastic properties of mucus gel that lines the stomachepithelial surface. The rheology of mucin is influenced by infection with the gastric ulcer and cancer causing bacteria,Helicobacter Pylori which swim across the mucus lining and colonize in the harsh acidic environment of the stomach. In thistalk we present results on microrheology obtained by tracking spherical tracer particles in culture broth solution and in solutionsof pig gastric mucin. The elastic and viscous moduli obtained by tracking particles in the mucin solutions are found to decreasein the presence of bacteria. We also examined the Brownian motion of the bacteria themselves and found that both motile andimmotile bacteria can be used to probe the local rheology of mucin solutions and gels. We observed that in mucin solutionsmotile bacteria display super-diffusive anomalous Brownian motion implying that bacteria reduce the effective viscosity of themucin solution. In contrast, the immotile bacteria exhibit regular diffusive Brownian motion. Results at different pH will bepresented.