Physics

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Abstract

Microbial locomotion is well understood when cells use either a small number of flagella or a high density of cilia. However many microbes live in an intermediate regime where coordination strategies such as flagellar bundles and metachronal waves are not possible. The mechanisms by which such organisms coordinate the motion of their swimming appendages are not well understood. Here, we study the only known obligatory multicellular bacterium, which are of the genus Magnetoglobus. Cells of this genus live exclusively in spherical communities called consortia, which are composed of a monolayer of tens of cells. Approximately a thousand of flagella project outward from the surface of each consortium, enabling swimming at speeds up to 190 μm/s. We reconstruct the velocity field around the swimming Magnetoglobus consortia using microparticle image velocimetry. The measured flow field is that of a nearly neutral squirmer and the observed subtle fore–aft asymmetry indicates propulsion dominated by a localized active region near the forward pole, producing a weak puller-type signature. The fore-aft asymmetry of the flow decays monotonically with increasing swimming speed. This relationship is described well by a phenomenological model in which flagella near one pole entrain the rotation of flagella within a certain correlation length which varies across individuals. These results provide the first measured flow field around a magnetotactic bacterium and provides a quantitative description of how hundreds to thousands of bacterial flagella can be coordinated on the surface of an individual.

Publication Date

Summer 6-5-2026

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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