MSE PhD Prospectus Defense of Clover Su

  • Starts: 1:00 pm on Wednesday, December 13, 2017
  • Ends: 3:00 pm on Wednesday, December 13, 2017
A Study of Bacterial Motility in Viscoelastic Media and the Chemotactic Responses of Helicobacter Pylori in Various Chemo-Gradients

ABSTRACT Helicobacter pylori is a bacterium that colonizes the human stomach and can cause gastric ulcers and cancer. While extensive studies have been published on the motility of H. pylori in various media, the majority of the studies were carried out in homogeneous environments and there is no publication on the motility of H. pylori in human mucins. The gastric mucosa where H. pylori lives exhibits various chemo-gradients, including a pH gradient varying from 2 to 7 across the mucus layer. The first part of the proposal presents the results on the microrheology and a live cell tracking study of the motility of H. pylori in healthy and tumor human mucins, Brucella broth, and purified porcine gastric mucin (PGM). The viscosity of human mucins was shown to be location and composition-dependent, with the gland mucin being more viscous than the surface mucin. The tumor mucin showed the lowest viscosity in comparison and its microrheology most influenced by the active bacterial motions. H. pylori exhibits broader swimming speed distribution and less reversal in human mucins as compared to PGM or Brucella broth. The second part of the proposal presents preliminary results on the influence of pH to the motility of H. pylori in Brucella broth and outlines a study of H. pylori chemotaxis to be carried out in various gradients utilizing microfluidic devices. H. pylori exhibited faster swimming speed at higher acidity in homogeneous environments over pH 3 to 6.3 and became immotile or died in a pH below 3. In response to the presence of a pH gradient, H. pylori travelled in directed trajectories at lower pH and more swimmers were observed at higher pH. The bacteria can detect the boundary between the regions of neutral and low pH, and were observed to reverse and move away from the low pH region. *Supported by NSF PHY 1410798

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