Abstract

Biology is dominated by transport problems involving fluid flows, from the transport of nutrients and locomotion to flows around plants and the circulatory system of animals. In this talk, I will discuss three instances of flows arising inside living cells.   First I will present our work modelling natural cytoplasmic streaming. The Drosophila embryo, an elongated multi-nucleated cell, is a classical model system for eukaryotic development and morphogenesis. We use mathematical modelling to characterise recent experiments showing that cytoplasmic flows, driven by cortical contractions along the walls of the embryo, enable the uniform spreading of nuclei along the anterior-posterior axis. By fitting the cortical contractions in our model to measurements, we reveal that experimental cortical flows enable near-optimal axial spreading of nuclei (https://doi.org/10.1098/rsif.2023.0428).    I will next discuss our work on artificial cytoplasmic streaming. Recent experiments have generated artificially induced intracellular flows using focused light localised in a small region of the cell to create a thermo-viscous flow globally inside the cell. I will present a theoretical model of the fluid flow induced by the focused light which shows excellent agreement with experimental results (https://doi.org/10.1103/PhysRevFluids.8.034202) .    Finally, I will address the recent controversial issue of convection flows inside cells. Recent computations have predicted that a temperature differential of ~1K between nucleus and cell membrane could be strong enough to drive significant intracellular material transport. Using numerical computations and theoretical calculations I will provide robust estimates for this cytoplasmic natural convection, which will demonstrate that these are much weaker than previously predicted and have a negligible contribution toward enhancing the diffusion-dominated mass transfer of cellular material.