Asymmetric random walks reveal that the chemotaxis network modulates flagellar rotational bias in <i>Helicobacter pylori</i>.

Abstract

The canonical chemotaxis network modulates the bias for a particular direction of rotation in the bacterial flagellar motor to help the cell migrate toward favorable chemical environments. How the chemotaxis network in <i>Helicobacter pylori</i> modulates flagellar functions is unknown, which limits our understanding of chemotaxis in this species. Here, we determined that <i>H. pylori</i> swim faster (slower) whenever their flagella rotate counterclockwise (clockwise) by analyzing their hydrodynamic interactions with bounding surfaces. This asymmetry in swimming helped quantify the rotational bias. Upon exposure to a chemo-attractant, the bias decreased and the cells tended to swim exclusively in the faster mode. In the absence of a key chemotaxis protein, CheY, the bias was zero. The relationship between the reversal frequency and the rotational bias was unimodal. Thus, <i>H. pylori</i>'s chemotaxis network appears to modulate the probability of clockwise rotation in otherwise counterclockwise-rotating flagella, similar to the canonical network.