Rotating Bacteria on Solid Surfaces without Tethering

Abstract

Bacterial motion is strongly affected by the presence of a surface. One of the hallmarks of swimming near a surface is a defined curvature of bacterial trajectories, underlining the importance of counter rotations of the cell body and flagellum for locomotion of the microorganism. We find that there is another mode of bacterial motion on solid surfaces, i.e., self trapping due to fluid flows created by a rotating flagellum perpendicular to the surface. For a rod-like bacterium, such as Escherichia coli, this creates a peculiar situation in that the bacterium appears to swim along a minor axis of the cell body and is pressed against the surface. Although a full hydrodynamic theory is still lacking to explain the self-trapping phenomenon, the effect is intriguing and can be exploited to study a variety of biophysical phenomena of swimming bacteria. In particular, we showed that self-trapped E. coli cells display a chemotaxis response that is identical to the classical rotation assay in which antibodies are used to physically ''glue'' a flagellum to the surface.

Transition to bound states for bacteria swimming near surfaces

“…Finally, we note that the surface-binding phenomena have been observed with at least two different bacterial species, namely, E. coli [34,35] and Serratia marcescens [36], both 10 times smaller than T. majus cells but possessing an elongated sphero-cylindrical cell body. Furthermore, in the case of Serratia marcescens, the cells became bound to an air-liquid interface in the same way as T. majus cells, suggesting that the surface binding mechanism described here is not just restricted to solid surfaces.…”

Asymmetric random walks reveal that the chemotaxis network modulates flagellar rotational bias in Helicobacter pylori

“…This is problematic as the cell can appear to be tethered but instead it pivots about its non-flagellated pole on a surface while the free rotation of the invisible filament causes the cell to rotate. This can lead to the mischaracterization of the direction of flagellar rotation, and therefore the rotational bias ( Dominick and Wu, 2018 ; Lele et al, 2016 ; Chawla et al, 2020 ). Alternately, the signaling output has been determined via Förster resonance energy transfer-based measurements of in vivo enzymatic reactions ( Sourjik et al, 2007 ).…”

Accurate delivery of chemicals to a small target using a pressure-driven valved micropipette

“…We used a mutant XLWU100 that was created from RP437, a widely used strain for chemotaxis studies. To create XLWU100, we knocked out iC on the bacterial chromosome using P1 transduction [8]. A mutant expressing sticky iC was supplied by the plasmid pDF313, which was transformed into XLWU100 [9].…”