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Award Details

Biophysical mechanisms driving spatial organization in bacterial cells

Research Details
Competition Year: 2017 Fiscal Year: 2017-2018
Project Lead Name: Weber, Stephanie Institution: McGill University
Department: Biology - Biology Province: Québec
Award Amount: $45,000 Installment: 1 - 5
Program: Discovery Grants Program - Individual Selection Committee: Genes, Cells and Molecules
Research Subject: Bacteriology Area of Application: Advancement of knowledge
Co-Researchers: No Co-Researcher Partners: No Partners
Award Summary

Living cells are divided into functional compartments called organelles. In eukaryotes, membranes create a diffusion barrier between organelles and the cytoplasm, such that each compartment maintains a distinct biochemical composition that is tailored for its particular function. The biophysical mechanisms underlying the structure and function of membrane-bound organelles are well understood. However, cells also contain organelles that are not enclosed by membranes. For example, stress granules, P bodies and the nucleolus belong to a class of membraneless organelles called "cellular bodies". These bodies consist of local concentrations of proteins and nucleic acids that rapidly exchange with the surrounding cytoplasm or nucleoplasm. Recent evidence suggests that cellular bodies assemble by liquid-liquid phase separation, during which soluble molecules condense from the cytoplasm (or nucleoplasm) to form concentrated liquid-like organelles. My postdoctoral work on the nucleolus, a large cellular body responsible for ribosome biogenesis, was instrumental in defining phase separation as a new mechanism for intracellular organization.

Here, I propose to investigate these concepts in a new biological context: bacteria. Since prokaryotes typically lack membrane-bound organelles, phase separation could provide an alternate mechanism for spatial and functional organization in this domain of life. My lab will explore this idea using transcription foci in E. coli. Transcription foci are clusters of RNA polymerase that appear to be structural and functional analogs of the nucleolus. Therefore, I hypothesize that TF are cellular bodies that (i) assemble by phase separation and (ii) function to accelerate ribosome biogenesis.

To test this hypothesis, we will combine live-cell fluorescence microscopy, quantitative image analysis and physical modeling. The discovery of cellular bodies in prokaryotes will establish a new paradigm for intracellular organization and demonstrate the universality of phase separation as an organizing principle that extends across the entire tree of life.