Project Details
Projekt
Heterogeneity in Colicin E2 expression of Escherichia coli
Subject Area
Metabolism, Biochemistry and Genetics of Microorganisms
Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
Term
from 2012 to 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 217673565
Bacteria possess several mechanisms enabling them to respond to changing and unfavorable environmental conditions or to outcompete other bacteria. One particular mechanism is the production and the release of toxins such as bacteriocins. Current research focuses on production, release and uptake of these toxins by bacteria. However, little is known about the quantitative aspects of the underlying gene regulatory processes. In the first funding period, we quantitatively studied the expression dynamics of the Colicin E2 operon in E. coli on a single cell level using fluorescence time-lapse microscopy. We were able to show that heterogeneous timing is characteristic for Colicin E2 expression at low concentrations of the exogeneous stressor Mitomycin C (MitC), while high concentrations of the exogenous stressor lead to a synchronized stress response of all cells. In the next funding period, we aim to understand the molecular mechanisms underlying Colicin gene expression during SOS response. Extending our previous analysis we are in particular interested how gene expression responds to time-varying environmental conditions. Our approach will be modular: Upon studying cea and cel expression in a broad set of mutant strains we will address the regulatory mechanisms in the various modules of the Colicin E2 system separately and in combination. Due to the complexity of the system it will be essential to closely integrate experimental and theoretical analysis in order to disentangle the relative role of and the interplay between the regulatory elements at the transcriptional and the post-transcriptional level. The experimental analysis will provide large ensembles of time traces for fluorescence reporters of the cea and cel genes for the different mutant strains whose statistical properties will be compared in detail with the results obtained from stochastic simulations of corresponding mathematical models. This will allow us to arrive at a detailed molecular understanding in a bottom-up fashion. These analyses will then lead to a molecular understanding of how the different modules regulating Colicin E2 expression are activated in dependence on given environmental conditions. In particular, this should give us a deeper insight into what causes the observed heterogeneous timing at low stress levels, and how the transition towards a synchronized response of the whole cell population is regulated. Finally, we want to study how phenotypic heterogeneity is passed on within growing bacterial microcolonies. Here, we want to understand if either a Colicin-dependent feedback acting on neighboring Colicin producing cells, or cell density (quorum sensing) affect the fraction of cells expressing Colicin E2. These experiments shall enable us to better understand the biological significance of heterogeneous Colicin E2 expression and how it is sustained within growing microcolonies.
DFG Programme
Priority Programmes
