Phases of active matter composed of multicellular magnetotactic bacteria near a hard surface
Phys. Rev. Fluids 7, 053102 – Published 27 May, 2022
DOI: https://doi.org/10.1103/PhysRevFluids.7.053102
Abstract
We investigate the motion of multicellular magnetotactic bacteria (MMB) near a hard surface. Directing MMB towards a flat surface causes them to accumulate about the wall as an active gas. MMB are exponentially distributed about the surface with a penetration depth determined by the typical distance an MMB swims before it aligns with the ambient field. Increasing the magnetic field past a critical value, at which the penetration depth is of order the size of an MMB, causes the active gas to condense into a two-dimensional active fluid. Measurements of MMB motion in this phase reveal that contact with the surface enhances rotational diffusion by a factor of 8 and that velocity fluctuations are Laplace distributed. The fluid undergoes a percolation transition at a critical magnetic field. Supercritical active fluids exhibit dynamic voids, which limit the relaxation of density fluctuations. We describe the possible ecological significance of these results.
