Prof. Dr. Marco Mazza (Loughborough U, MPG Göttingen): Emergent probability fluxes in confined microbial navigation: finding order from chaos
In recent years, biological motile cells like bacteria and microalgae have attracted considerable interest not only among biologists but also in the physics community and related fields. Understanding their motion has immense biological and ecological implications. The possibility to harness their motion to power microdevices is a topic of exceptional importance for modern microtechnology. When the motion of a motile cell is observed closely, it appears erratic, and yet the combination of nonequilibrium forces and surfaces can produce striking examples of organization in microbial systems. While our current understanding is based on very simple environments, it remains elusive how, and, at which length scale self-organization emerges in complex geometries. Combining experiments, analytical and numerical calculations [1,2] we study the motion of motile cells under controlled lab conditions and demonstrate that intricate patterns can be observed even at the level of a single cell exploring an isolated habitat. We can explain how curvature guides the motion of the cell. We theoretically predict a universal relation between probability fluxes and global geometric properties that is directly confirmed by experiments . Our results represent a general description of the structure of such nonequilibrium fluxes down at the single cell level. This might open the possibility of designing devices that are able to guide the motion of such microbial cells.  J. Cammann et al., Proc. Natl. Acad. Sci. 118, e2024752118 (2021).  T. Ostapenko et al., Phys. Rev. Lett. 120, 068002 (2018).