Howard Berg

Harvard University

Motile Behavior of E. coli: Navigation by a Single-celled Nervous System

12:00 pm, Tuesday 06 October 2015

Location: Oxford Martin School, Old Indian Institute, 34 Broad Street, Oxford

Abstract: Much is known about the motile behavior of the bacterium Escherichia coli. Early work on tracking E. coli and learning about its biased random walk was followed by the realization that bacterial flagella rotate rather than wave or beat. Flagellar rotation is controlled by chemoreceptors at the cell surface. Receptor methylation is required for adaptation on the second time scale, which enables cells to make temporal comparisons and swim up spatial gradients of attractants. Without methylation, one still observes partial adaptation, on the minute time scale, as motors remodel and shift their operating points. Motors also adapt to changes in viscous load. When the load suddenly increases, additional force-generating units are added one by one; thus, the flagellum is a mechanosensor as well as a device for generating thrust. Flagellar filaments grow at their distal ends at a rate that does not to depend upon initial lengths. Single-file diffusion appears to be adequate to get flagellin subunits from the base to the tip.

Biography: Howard Berg is the Herchel Smith Professor of Physics and Professor of Molecular and Cellular Biology at Harvard University. He was a chemist (B.S., Caltech); a medical student (two years at Harvard Medical School); and then a graduate student in physics and Junior Fellow at Harvard. Berg now thinks of himself “as a neurobiologist, but one who has had the courage to deal only with the simplest single-celled nervous systems.” He is a member of the US National Academy of Sciences and the American Philosophical Society.

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