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This paper provides a theoretical framework to understand the effect of single cell growth and division on evolutionary dynamics via population dynamic studies. It connects processes of single cell scale to population dynamics. By first developing a comprehensive model incorporating Stochastic Differential Equations for evolution of rare mutations in an evolving population and linking this model to single cell scale using population growth dynamics equations, the authors develop a predictive theory of microbial evolution. In particular, they provide a theory for predicting conditions for genetic drift and fixation probabilities of mutants in a large population. Their work is exceptional as it focuses on division rate fluctuations without assuming age distribution to be in a steady state or discrete age classes. They also demonstrate that such approximations aren’t valid for physiologically relevant models of microbial growth. By generalization of continuous time Moran processes, derived for physiological models of growth, division and cell age control, the authors derive Fokker-Plank equations for the genotype frequencies. This is then used to predict equations and conditions for fixation probabilities and genetic drift under Neutral and Adaptive evolution strategies. Generally classical theory predicts linear increase in fitness with time by relying on selection coefficient, however, their model shows the insufficiency of this coefficient because of non-linear fitness trajectories in long-term evolutionary dynamics. 

The paper is comprehensive in theory however, it lacks experimental support and validation.

Competing interests

The author declares that they have no competing interests.