Abstract
Microbial populations show striking diversity in cell growth morphology and lifecycle; however, our understanding of how these factors influence the growth rate of cell populations remains limited. We use theory and simulations to predict the impact of asymmetric cell division, cell size regulation and single-cell stochasticity on the population growth rate. Our model predicts that coarse-grained noise in the single-cell growth rate λ decreases the population growth rate, as previously seen for symmetrically dividing cells. However, for a given noise in λ we find that dividing asymmetrically can enhance the population growth rate for cells with strong size control (between a "sizer" and an "adder"). To reconcile this finding with the abundance of symmetrically dividing organisms in nature, we propose that additional constraints on cell growth and division must be present which are not included in our model, and we explore the effects of selected extensions thereof. Further, we find that within our model, epigenetically inherited generation times may arise due to size control in asymmetrically dividing cells, providing a possible explanation for recent experimental observations in budding yeast. Taken together, our findings provide insight into the complex effects generated by non-canonical growth morphologies.
Highlights
Recent years have expanded our understanding of heterogeneity at the single cell level, with clonal populations displaying variability in a range of physiological parameters, including cell generation times, cell size and gene expression [1–5]
We show that cell division asymmetry can have a strong impact on the population growth rate
This simplification does not hold in the case of correlated generation times, which have been observed in a range of organisms [4, 5, 13,14,15], meaning the full tree distribution is required for Eq 1 to hold
Summary
Recent years have expanded our understanding of heterogeneity at the single cell level, with clonal populations displaying variability in a range of physiological parameters, including cell generation times (the time between cell birth and division), cell size and gene expression [1–5]. Studies incorporating cell size control predict that the single cell exponential growth rate λ sets ΛP, with ΛP = λ exactly in the absence of noise in their single cell growth rate [6]. This can be readily shown by requiring that the cell size distribution reaches steady state with a constant average size hVi, since hVi(t) = ∑i Vi(t)/N(t) / exp[(λ − ΛP)t] = constant , where Vi is the volume of each cell i in the population and N(t) is the population number at time t.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
