The Function of the Na ⁺ -Driven Flagellum of Vibrio cholerae Is Determined by Osmolality and pH

Abstract

bVibrio cholerae is motile by its polar flagellum, which is driven by a Na ؉ -conducting motor. The stators of the motor, composed of four PomA and two PomB subunits, provide access for Na ؉ to the torque-generating unit of the motor. To characterize the Na ؉ pathway formed by the PomAB complex, we studied the influence of chloride salts (chaotropic, Na ؉ , and K ؉ ) and pH on the motility of V. cholerae. Motility decreased at elevated pH but increased if a chaotropic chloride salt was added, which rules out a direct Na ؉ and H ؉ competition in the process of binding to the conserved PomB D23 residue. Cells expressing the PomB S26A/T or D42N variants lost motility at low Na ؉ concentrations but regained motility in the presence of 170 mM chloride. Both PomA and PomB were modified by N,N=-dicyclohexylcarbodiimide (DCCD), indicating the presence of protonated carboxyl groups in the hydrophobic regions of the two proteins. Na ؉ did not protect PomA and PomB from this modification. Our study shows that both osmolality and pH have an influence on the function of the flagellum from V. cholerae. We propose that D23, S26, and D42 of PomB are part of an ion-conducting pathway formed by the PomAB stator complex.

Roles of the Sodium-Translocating NADH:Quinone Oxidoreductase (Na+-NQR) on Vibrio cholerae Metabolism, Motility and Osmotic Stress Resistance

“…The endogenous Na + content of the medium was 11 mM as determined by atomic absorption spectroscopy [17]. If indicated, D,L-lactate (33 mM final concentration) was added from a stock solution adjusted to pH 6.5 with KOH.…”

Response of Vibrio cholerae to the Catecholamine Hormones Epinephrine and Norepinephrine

“…V. cholerae O395, devoid of the qseC-like gene, exhibited reduced motility on serum-SAPI compared to the reference strain, but motility was still enhanced by E or NE, suggesting the presence of additional systems for catecholate sensing, like QseE, BasS, or CpxA (37). Expression levels of the pomB gene coding for a structural component of the flagellar stator complex (38) and the qseC-like gene were increased when V. cholerae was exposed to E or NE. This indicates an NE-or E-triggered signal transduction chain in V. cholerae, which might be related to the QseC-dependent signaling cascades described for S. enterica (4) and E. coli (29,39).…”

The Ecological Coherence of Temperature and Salinity Tolerance Interaction and Pigmentation in a Non-marine Vibrio Isolated from Salar de Atacama

“…was also affected by the presence of NaCl ( Figure 4 ) and, perhaps, specifically by chloride ions (data not shown). Halang et al (2013) reported that in V. cholerae chloride ions act as chaotropic agents and enhance cell motility. For instance, the nano-machine flagellum is composed of several subunits, MotA and MotB in H + -dependent, or PomA and PomB in Na + -dependent flagella (Halang et al, 2013).…”

“…Halang et al (2013) reported that in V. cholerae chloride ions act as chaotropic agents and enhance cell motility. For instance, the nano-machine flagellum is composed of several subunits, MotA and MotB in H + -dependent, or PomA and PomB in Na + -dependent flagella (Halang et al, 2013). Chloride ions disrupt hydrogen bonds between water molecules that interact with PomB protein, specifically with D23 and S26 residues.…”