Linda Turner Stern
Rowland Institute at Harvard
100 Edwin H. Land Blvd.
Cambridge, MA 02142
Phone: 617-497-4606, Fax: 617-497-4627
I am interested in the motility of micro-organisms, especialy how bacteria swim (move as individuals in a liquid) and swarm (move in coordinated packs across a surface). During both behaviors the bacterial flagellar filament propels the bacterium. This filament is composed of many copies of a single protein, called flagellin, arranged in a spiralling path on a cylindrical surface. The overall shape of the filament is helical. Remarkably, this rigid helical propellor changes shape, undergoing polymorphic transformations, as the bacterium swims and swarms. I enjoy thinking about the relationship between applied motor torque, transformation, hydrodynamics, and behavior. I use fluorescent labeling and video microscopy (both high speed and color imaging) to understand the role of the flagellum in cell behavior.
Recently I completed a study on how filaments grow, see below image. It is intriguing how the flagellum is assembled, and to think about what limits the filament length. See and Fabienne Chevance's work for more on flagellar biogenesis.
A study of flagellar growth revealed that filament growth is independent of length. Cells of Escherichia coli strains carrying flagellin serine-to-cysteine substitutions were grown, labeled with a green Alexa Fluor maleimide dye, grown a second time, and labeled with a red Alexa Fluor maleimide dye. Regions of overlap between green and red images appeared yellow. Distributions of segment lengths were broad, but on average, the lengths of red segments did not depend upon the lengths of the green segments from which they grew. (See J. Bacteriol. 194 (10), 2437-24421 (2012))
Turner, L., Stern, A.S. and Berg, H.C. Growth of flagellar filaments is independent of filament length. J. Bacteriol. 194 (10), 2437-24421 (2012).
Yuan, J., Fahrner, K. A., Turner, L. and Berg, H. C. Asymmetry in the clockwise and counter-clockwise rotation of the bacterial flagellar motor. Proc. Natl. Acad. Sci. USA 107, 12846-12949 (2010).
Turner, L., Zhang, R., Darnton, N.C., and Berg, H.C. Visualization of flagella during bacterial swarming. J. Bacteriol. 192, 3259-3267 (2010).
Darnton, N.C., Turner, L, Rojevsky, S., and Berg, H.C. Dynamics of bacterial swarming. Biophys J. 28, 2082-2090 (2010).
Zhang, R., Turner, L. and Berg, H.C. The upper surface of an Escherichia coli swarm is stationary. Proc. Natl. Acad. Sci. USA 107: 288-290 (2010).
Hulme, S.E., DiLuzio, W.R., Shevkoplyas, S.S., Turner, L., Mayer, M., Berg, H.C. and Whitesides, G.W. Using ratchets and sorters to fractionate motile cells of Escherichia coli by length. Lab on a Chip xxx, 1-8 (2008)
Berke, A.P., Turner, L., Berg, H.C. and Lauga, E. Hydrodynamic attraction of swimming microorganisms by surfaces. Phys. Rev. Lett. 101, 038102 (2008)
Blair, K., Turner, L., Winkelman, J., Berg, H.C. and Kearns, D.B. A molecular clutch disables flagella in the Bacillus subtilis biofilm. Science 320, 1636-1638 (2008).
Chen, B.G., Turner, L. and Berg, H.C. The wetting agent required for swarming in Salmonella enterica serovar Typhimurium is not a surfactant. J Bacteriol. 189, 8750-8753 (2007).
Darnton, N., Turner, L., Rojevsky, S. and Berg, H.C. On torque and tumbling in swimming Escherichia coli. J. Bacteriol. 189, 1756-1764 (2007).
Yi, D.K., Kim, M.J., Turner, L., Breuer, K.S. and Kim, D. Colloid lithography-induced polydimethylsiloxane microstructures and their application to cell patterning. Biotechnol. Lett. 28, 169-173 (2006).
DiLuzio, W.R., Turner, L, Mayer, M., Garstecki, P., Weibel, D.B., Berg, H.C. and Whitesides, G.M. Escherichia coli
swim on the right-hand side. Nature 435, 1271-4 (2005).
Darnton, N., Turner, L., Breuer, K. and Berg H.C. Moving fluid with bacterial carpets. Biophys J. 86, 1863-70 (2004).
Turner, L., Ryu, W.S. and Berg, H.C. Real-time imaging of fluorescent flagellar filaments. J. Bacteriol. 182, 2793-2801 (2000).
Turner, L., Samuel, A.D.T., Stern, A.S. and Berg, H.C. Temperature dependence of switching of the bacterial flagellar motor by the protein CheY13DK106YW. Biophys. J. 77, 597-603 (1999).
Scharf, B.E., Fahrner, K.A., Turner, L. and Berg, H.C. Control of direction of flagellar rotation in bacterial chemotaxis. Proc. Natl. Acad. Sci. USA 95, 201-206 (1998).
Turner, L., Caplan, S.R. and Berg, H.C. Temperature-induced switching of the bacterial flagellar motor. Biophys. J. 71, 2227-2233 (1996).
Berry, R.M., Turner, L. and Berg, H.C. Mechanical limits of bacterial flagellar motors probed by electrorotation. Biophys. J. 69, 280-286 (1995).
Berg, H.C. and Turner, L. Cells of Escherichia coli swim either end forward. Proc. Natl. Acad. Sci. USA 92, 477-479 (1995).
Berg, H.C. and Turner, L. Torque generated by the flagellar motor of Escherichia coli. Biophys. J. 65, 2201-2216 (1993).
Berg, H.C. and Turner, L. Selection of motile nonchemotactic mutants of Escherichia coli by field-flow fractionation. Proc. Natl. Acad. Sci. USA 88, 8145-8148 (1991).
Berg, H.C. and Turner, L. Chemotaxis of bacteria in glass capillary arrays. Biophys. J. 58, 919-930 (1990).
Berg, H.C. and Turner, L. Movement of microorganisms in viscous environments. Nature 278, 349-351 (1979).
Other Professional Activities
Symposium Organizer, Material Research Society, Symposium AA: Molecular Motors,
Nanomachines and Engineered Systems, San Francisco, CA, April 17-21, 2006
Invited speaker, Frontiers in the Interaction between Physics and Biology, Spring 2004, Brown
University, Providence, RI
Contributor, National Nanotechnology Initiative, Workshop on NanoBiotechnology,
Oct. 2003 Arlington, VA
Invited speaker, American Society for Microbiology, Conference on Bio-, Micro-, and Nanosystems,
July 2003, NYC, NY