TEXAS TECH UNIVERSITY
Department of Mechanical Engineering
Mechanics of surface-attached bacterial systems on single-cell and multi-cellular
lengthscales
Dr. Vernita Gordon, Assistant Professor
Department of Physics, The University of Texas at Austin
Abstract: Biofilms are communities of interacting bacteria that are bound to each other and a surface by a
matrix of extracellular polymers. In a mechanical sense, biofilms can be thought of as a mixture of colloids
(bacteria) and polymer (extracellular matrix polymers). Biofilms initiate when non-biofilm bacteria attach to a
surface, sense the presence of the surface, and change their gene expression accordingly. The biofilm matrix
protects the biofilm by both mechanical and chemical means. Multiple types of matrix polymers can be
produced by a single bacterial strain - the reasons for this redundancy are not well-understood. In this talk, I will
present evidence from our lab suggesting that different polymers may confer distinct mechanical benefits. On the
single-cell level, these benefits may help bacteria form biofilms more efficiently, by responding more strongly to
the presence of a surface.
We characterize this using a combination of AFM force measurements and
fluorescence microscopy of bacteria that express a fluorescent protein to report gene activity. On the multicellular level characterizing the mature biofilm, different matrix polymers can toughen the biofilm either by
increasing its elastic modulus or by increasing its ductility. Decades-long biofilm infections in the lungs of
Cystic Fibrosis patients evolve in the patient's lung and change their patterns of polymer expression - these are
reflected in changes in the biofilm's viscoelastic mechanics. Mechanical changes may contribute to the ability of
biofilms to evade the human host's immune system. We characterize this using bulk rheology in a conventional
rheometer that has been lightly modified to allow measurements of these aqueous, biological systems.
Bio: Vernita Gordon has been an assistant professor of physics at The University of
Texas at Austin since 2010. She got her B.Sc. in Physics and Math from Vanderbilt
University in 1997, her Ph.D. in Physics from Harvard University in 2003, and postdoced
at University of Edinburgh and University of Illinois. She enjoys using physics to
understand disease-causing biological systems and think of new approaches to ameliorate
disease.
Monday, Jan 26 2015
Livermore Center 101 | 2:00 – 3:00 pm
Coordinator: Dr. Chang-Dong Yeo (changdong.yeo@ttu.edu)