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Single-Cell Biophysics: Measurement, Modulation, and Modeling
Monday Speaker Abstracts
26
Intrinsic and Extrinsic Noise in an Organelle Size Control System
Wallace Marshall
University of California, San Francisco, CA, USA
No Abstract
Cell-size Determination by the Bacterial Actin Cytoskeleton
Kerwyn C. Huang
.
Stanford, Stanford, CA, USA.
Changes in bacterial cell size are associated with critical changes in fitness and growth rate at the
single-cell level; at the population level, these changes affect biofilm formation and virulence.
To explore the relationships among genotype, structural phenotype, and bacterial physiology, we
constructed a library of
Escherichia coli
mutants with a range of cell sizes and used
fluorescence-activated cell sorting to identify subtle changes in cell shape, allowing us to query
the effect of cell shape on several physiological behaviors, growth rate, DNA content, and drug
sensitivity. The quantitative relationships revealed by this strategy highlight the complex and
dynamic links between bacterial morphology and physiology. In
E. coli
, the actin-like protein
MreB localizes in a curvature-dependent manner and spatially coordinates cell-wall insertion to
maintain cell shape across changing environments, although the molecular mechanism by which
cell width is regulated remains unknown. I will show that the bitopic protein RodZ regulates the
biophysical properties of MreB and alters the spatial organization of
E. coli
cell-wall growth.
The relative expression levels of MreB and RodZ changed in a manner commensurate with
variations in growth rate and cell width. We carried out molecular dynamics simulations and
single-cell analyses to determine that RodZ alters the curvature-based localization of MreB, and
therefore cell shape. Together, our results show that E. coli controls its shape and dimensions by
differentially regulating RodZ and MreB to alter the patterning of cell-wall insertion,
highlighting the rich regulatory landscape of cytoskeletal molecular biophysics.