SoftBio Theory Seminar - What dominates fluctuations of cellular growth rate?

Many cells exhibit exponential growth not only in population size but also at the single-cell level. However, single-cell growth rates fluctuate over time. We distinguish between two conceptually distinct sources of growth rate fluctuations: intrinsic continuous fluctuations resulting from intracellular processes, and fluctuations that originate at division events, which we refer to as kicks. We use a simple model to describe single-cell growth and identify the signatures of continuous noise and division kicks. To infer the true biological behavior accurately, it is crucial to account for measurement noise in experiments. We derive analytical expressions for the statistics of meaningful observables, taking into account continuous fluctuations, division kicks, and measurement noise. Importantly, we find that ignoring measurement noise can lead to incorrect biological conclusions. Our results provide insights into how different sources of growth rate variability and measurement errors influence observed cell size dynamics, with implications for interpreting experimental data in cellular biology.