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BEGIN:VEVENT
DTSTAMP:20261018T231847Z
LAST-MODIFIED:20181116T152507Z
DTSTART:20181207T160000Z
DTEND:20181207T170000Z
UID:event2034@bu.edu
URL:http://physics.bu.edu/internal/events/show/2034
SUMMARY:INFLUENCE OF ACID ON MOTILITY AND CHEMOTACTIC RESPONSE OF HELICOBAC
	TER PYLORI IN GASTRIC MUCIN 
DESCRIPTION:Featuring Ting-Yi (Clover) Su\n\nPart of the PhD Final Oral Exa
	ms.\n\nDespite the highly acidic environment of the human stomach\, Helicob
	acter pylori inhabits the gastric mucosa of half of the world population. W
	hile a fraction of the infected individuals develop gastric diseases\, the 
	presence of H. pylori has also been linked to benefits such as protection a
	gainst allergies. The pathogenic and beneficial aspects of the bacteria req
	uire intricate balance in its motility\, colonization and interaction with 
	the host. In this dissertation I focus on understanding the factors that in
	fluence motility. The first part of this dissertation presents a comparison
	 of the microrheology and the bacterial motility in healthy and tumor human
	 gastric mucins. Active bacteria motion led to shear-thinning of the mucin 
	solution and decreased its viscosity. The tumor mucin showed the lowest vis
	cosity and its microrheology was most affected by bacterial motion. The sec
	ond part of the dissertation elucidates the interplay between acidity and g
	astric mucin microrheology on motility. H. pylori motility shows a non-mono
	tonic pH dependence\, with the median of speed distribution peaking at pH4 
	in aqueous broth\, below which the flagella motors fail due to high externa
	l proton concentration and bacteria become immotile below pH3. In contrast\
	, in mucin the viscosity dominates motility; the median speed peaks at pH5 
	related to the approaching sol-gel transition around pH4. Additionally\, th
	e cell rotation increases monotonically with decreasing pH in mucin\, imply
	ing that bacteria sense mechanical stress and increase rotation in an attem
	pt to escape from mucin gel. The last part of the thesis examines chemotaxi
	s of H. pylori in presence of a linear pH gradient in broth using single-ch
	annel microfluidics. The chemotaxis of H. pylori was most prominent at pH3-
	4.5; below pH3 the bacteria is immotile and above pH4.5 the bacteria resume
	 random swimming directions. Individual\, directed trajectories suggest tha
	t bacteria slow down upon reaching pH5. Lastly\, a microfluidic assay was d
	eveloped to explore the viscous fingering of gastric acid in mucin. With pr
	oper injection pressure\, single acid channels can be created in mucin solu
	tions. Microrheology analysis reveals that mucin gels and swells in the vic
	inity of the acid channel\, which squeezes the acid in forming a thin finge
	r pattern.\n\n\nCommittee Members\, Dept Affiliations\nProfessor Rama Bansi
	l\, Physics and MSE\nProfessor Maria (Masha) Kamenetska\, Physics and Chemi
	stry\nProfessor Kirill Korolev\, Physics\nProfessor James Bird\, MSE and ME
	\nProfessor Basu\, MSE and ME
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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