Semester 2, Week 6: Prof John Mackenzie, University of Strathclyde

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Title: Dissecting the Role of Phenotypic Variation in Cell Population Growth and Collective Self-Generated Chemotaxis

Abstract:

Phenotypic variation is a ubiquitous feature of biological cell populations, even in genetically identical cells growing in uniform environments. Such variability can have profound consequences for population-level behaviour, particularly under stress, yet it is often neglected in classical modelling frameworks.

In the first part of this talk, I consider mathematical models of bacterial population growth that explicitly incorporate non-heritable variation in individual cell growth rates. I examine how phenotypic heterogeneity and environmental selection shape population growth and the dynamics of phenotypic subpopulations. We derive theoretical results for population growth rates and compare them with predictions from homogeneous models, identifying regimes in which variability qualitatively alters population outcomes. I also address the inverse problem of inferring distributions of generation times and phenotypic abundances from data, showing that competing model assumptions can be robustly distinguished.

In the second part of the talk, I turn to self-generated chemotaxis, a collective process in which cells modify their chemical environment to guide movement. Using a hybrid discrete–continuum model that couples stochastic cell motion with a continuum description of the chemoattractant, I investigate how phenotypic variation in motility, sensing, and chemical degradation affects the robustness of collective migration. Simulations and inference results highlight which sources of variability are most influential. The results and tools developed have broader implications for collective behaviour in cell biology, ecology, and evolution.

Location/Time: Maths Lecture Theatre B