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CATEGORIES:PhD Defense
DESCRIPTION:Title: Physical structures and properties of the Gram-negative 
 cell envelope\n\nAbstract: The bacterial cell envelope is essential for mai
 ntaining cell integrity while supporting growth and division. In Gram-negat
 ive bacteria\, it consists of three distinct layers: the cytoplasmic membra
 ne (CM)\, a rigid peptidoglycan cell wall (CW)\, and an asymmetric outer me
 mbrane (OM). Although the cell relies on the envelope for viability\, shape
  maintenance\, and mechanical integrity\, the physical structures and prope
 rties underlying these functions remain largely understudied\, limiting the
  development of strategies to destabilize the bacterial envelope. This thes
 is employs a biophysical approach to investigate two important envelope str
 uctures\, revealing a mechanical role for MreB filaments as potential linke
 rs between the CM and the CW\, and identifying molecular interactions that 
 control OM fluidity.\n\nThe bacterial actin homolog MreB is crucial for cel
 l shape determination in many rod-shaped bacteria. Using microfluidics to a
 pply oscillatory hyperosmotic shocks\, we found that MreB mechanically coup
 les the CM to the CW\, thereby combining the two layers for improved load-b
 earing capacity. The MreB-mediated linkage\, especially at the cell poles\,
  is sufficient to resist plasmolysis\, indicating that MreB is the major me
 chanical connection between the two layers.\n\nThe OM is a versatile layer 
 that protects the cell with its selective permeability and mechanical stiff
 ness. Unlike most lipid bilayers such as the fluid CM\, the OM exhibits ext
 remely limited lateral diffusion\, resulting in spatial heterogeneity. Usin
 g fluorescence recovery after photobleaching assay alongside genetic and ch
 emical perturbations\, we identified key molecular interactions affecting O
 M fluidity\, including increased phospholipids in the outer leaflet that fl
 uidize the OM. Increased OM fluidity was found to be associated with shorte
 r cells through altered divisome dynamics\, linking envelope properties to 
 the regulation of bacterial cell body plan.\n\nPlease contact Madelyn Berns
 tein for the Zoom link
DTEND:20250428T220000Z
DTSTAMP:20260412T191229Z
DTSTART:20250428T210000Z
GEO:37.431924;-122.1767
LOCATION:Beckman Center\, Munzer Auditorium
SEQUENCE:0
SUMMARY:PhD Dissertation Defense: Jiawei Sun
UID:tag:localist.com\,2008:EventInstance_49420058761257
URL:https://events.stanford.edu/event/phd-dissertation-defense-jiawei-sun
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