From single-cell variability to population growth

TL;DR

This paper develops a biologically relevant model linking single-cell growth variability and correlations to population growth rate, challenging previous assumptions of uncorrelated generation times.

Contribution

It introduces a new model incorporating correlated exponential growth and fluctuating growth rates, improving understanding of population dynamics.

Findings

Population growth rate depends only on single-cell growth rate distribution.

Correlations in growth rates significantly influence population growth.

Model aligns better with observed cell size control mechanisms.

Abstract

Single-cell experiments have revealed cell-to-cell variability in generation times and growth rates for genetically identical cells. Theoretical models relating the fluctuating generation times of single cells to the population growth rate are usually based on the assumption that the generation times of mother and daughter cells are uncorrelated. This assumption, however, is inconsistent with the exponential growth of cell volume in time observed for many cell types. Here we develop a more general and biologically relevant model in which cells grow exponentially and generation times are correlated in a manner which controls cell size. In addition to the fluctuating generation times, we also allow the single-cell growth rates to fluctuate and account for their correlations across the lineage tree. Surprisingly, we find that the population growth rate only depends on the distribution of single-cell growth rates and their correlations.