Bulletin of the American Physical Society
2017 Annual Meeting of the Far West Section
Friday–Saturday, November 3–4, 2017; Merced, California
Session A1: Friday Plenary |
Hide Abstracts |
Chair: Hendrik Ohldag, SLAC National Accelerator Laboratory Room: COB2 130 |
Friday, November 3, 2017 10:30AM - 11:15AM |
A1.00001: Our Galactic Center: A Unique Laboratory for the Physics & Astrophysics of Black Hole Invited Speaker: Andrea Ghez The proximity of our Galaxy's center presents a unique opportunity to study a galactic nucleus with orders of magnitude higher spatial resolution than can be brought to bear on any other galaxy. After more than a decade of diffraction-limited imaging on large ground-based telescopes, the case for a supermassive black hole at the Galactic center has gone from a possibility to a certainty, thanks to measurements of individual stellar orbits. The rapidity with which these stars move on small-scale orbits indicates a source of tremendous gravity and provides the best evidence that supermassive black holes, which confront and challenge our knowledge of fundamental physics, do exist in the Universe. This work was made possible through the use of speckle imaging techniques, which corrects for the blurring effects of the earth's atmosphere in post-processing and allowed the first diffraction-limited images to be produced with these large ground-based telescopes. Further progress in high-angular resolution imaging techniques on large, ground- based telescopes has resulted the more sophisticated technology of adaptive optics, which corrects for these effects in real time. This has increased the power of imaging by an order of magnitude and permitted spectroscopic study at high resolution on these telescopes for the first time. With adaptive optics, high resolution studies of the Galactic center have shown that what happens near a supermassive back hole is quite different than what theoretical models have predicted, which changes many of our notions on how galaxies form and evolve over time. By continuing to push on the cutting-edge of high-resolution technology, we will be able to capture the orbital motions of stars with sufficient precision to test Einstein’s General theory of Relativity as well as theories of galaxy formation and evolution - all in regimes that have never been probed before. [Preview Abstract] |
Friday, November 3, 2017 11:15AM - 12:00PM |
A1.00002: The Physics of Bacterial Growth and Form Invited Speaker: Kerwyn Huang Cells typically maintain characteristic shapes, but the mechanisms of self-organization for robust morphological maintenance remain unclear in most systems. In this talk, I will describe how we have interrogated this complex question at multiple length scales using a combination of molecular and cellular mechanochemical simulations and novel imaging techniques. Precise regulation of rod-like shape in Escherichia coli cells requires the MreB actin-like cytoskeleton, but the mechanism by which MreB maintains rod-like shape is unknown. We have used time-lapse and 3D imaging coupled with computational analysis to map the growth, geometry, and cytoskeletal organization of single bacterial cells at subcellular resolution. Our results demonstrate that feedback between cell geometry and MreB localization maintains rod-like cell shape by targeting cell wall growth to regions of negative cell wall curvature. Pulse-chase labeling indicates that growth is heterogeneous and correlates spatially and temporally with MreB localization, whereas MreB inhibition results in more homogeneous growth, including growth in polar regions previously thought to be inert. Biophysical simulations establish that curvature feedback on the localization of cell wall growth is an effective mechanism for cell straightening and suggest that surface deformations caused by cell wall insertion could direct circumferential motion of MreB. Molecular dynamics simulations show that MreB filaments have tunable curvature and twisting that can explain the cell wall patterning observed in experiments. We also demonstrate that the bitopic protein RodZ regulates the biophysical properties of MreB and alters the spatial organization of new cell wall growth in Escherichia coli. We find that the relative expression of MreB and RodZ change in a manner commensurate with variations in growth rate and cell width. We present molecular dynamics simulations and quantitative microscopy demonstrating that RodZ alters the curvature sensitivity of MreB, and cell shape as a consequence. Finally, we identify MreB mutants that mimic the molecular properties of RodZ binding, and that rescue cell shape in the absence of RodZ . Together, our results describe how E. coli alters its cell width by differentially regulating RodZ and MreB to alter the patterning of cell wall insertion. Our findings indicate the potential for rich regulatory landscape of MreB molecular biophysics that can drive changes in cell shape across bacteria. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700