Abstract

Unraveling the motion of microorganisms in dilute and porous media is important for our understanding of both the molecular basis of their swim gait and their survival strategies in microbial habitats. First, I will show that by using renewal processes to analyze experimental measurements of wild-type {\it E. Coli}, we can provide a quantitative spatiotemporal characterization of their run-and-tumble dynamics in bulk [1,2]. We further demonstrate quantitatively how the persistence length of an engineered strain can be controlled by a chemical inducer and characterize a transition from perpetual tumbling to smooth swimming. Second, I will address how this run-and-tumble gait evolves towards a hop-and-trap motility pattern of agents moving in a porous environment [3]. Using computer simulations, we discover a geometric criterion for their optimal spreading, which emerges when their persistence lengths are comparable to the longest straight path available in the porous medium. Our criterion provides a fundamental principle for optimal transport in densely-packed biological and environmental settings, which could be tested experimentally by using engineered cells and may provide insights into microbial adaption mechanisms.

[1] C Kurzthaler, Y Zhao et al. Phys. Rev. Lett. 132 (2024)

[2] Y Zhao, C Kurzthaler et al. Phys. Rev. E 109 (2024)

[3] C Kurzthaler et al. Nat. Commun. 12, 7088 (2021)