ZomB is essential for flagellar motor reversals in Shewanella putrefaciens and Vibrio parahaemolyticus

Abstract

The ability of most bacterial flagellar motors to reverse the direction of rotation is crucial for efficient chemotaxis. In Escherichia coli, motor reversals are mediated by binding of phosphorylated chemotaxis protein CheY to components of the flagellar rotor, FliM and FliN, which induces a conformational switch of the flagellar C-ring. Here, we show that for Shewanella putrefaciens, Vibrio parahaemolyticus and likely a number of other species an additional transmembrane protein, ZomB, is critically required for motor reversals as mutants lacking ZomB exclusively exhibit straightforward swimming also upon full phosphorylation or overproduction of CheY. ZomB is recruited to the cell poles by and is destabilized in the absence of the polar landmark protein HubP. ZomB also co-localizes to and may thus interact with the flagellar motor. The ΔzomB phenotype was suppressed by mutations in the very C-terminal region of FliM. We propose that the flagellar motors of Shewanella, Vibrio and numerous other species harboring orthologs to ZomB are locked in counterclockwise rotation and may require interaction with ZomB to enable the conformational switch required for motor reversals. Regulation of ZomB activity or abundance may provide these species with an additional means to modulate chemotaxis efficiency.

The GGDEF Domain of the Phosphodiesterase PdeB in Shewanella putrefaciens Mediates Recruitment by the Polar Landmark Protein HubP

“…The double deletion had an additive effect, indicating that both proteins mediate different aspects of swimming. In contrast, for cells equipped with the lateral flagellar system only (ΔflaA 2 B 2 strain), which is not addressed by the chemotaxis system or ZomB (19,43) and for which, so far, no direct effect mediated by HubP is reported, no such additive effect was observed. The absence of HubP also reduced spreading to about 70% of that of the wild type and did not further reduce spreading by ΔpdeB mutants (both at about 50% of that of wild-type cells), indicating that for the lateral flagellar system, PdeB is epistatic to HubP.…”

“…The phosphodiesterase PdeB affects swimming of S. putrefaciens CN-32. Earlier transposon mutagenesis and screening for defects in swimming motility (19) identified Sputcn32_3405 as a positive determinant for spreading in soft agar. This gene encodes a potential ortholog of S. oneidensis MR-1 PdeB (42) as the two proteins share the same domain organization and have 79% identity and 87% similarity at the amino acid level for the complete protein.…”

“…HubP has been demonstrated to also directly or indirectly affect flagellum-mediated motility in S. putrefaciens, e.g., by recruitment of the chemotaxis cluster and stabilizing the motor-affecting protein ZomB (11,19) and likely other, yet unidentified, factors. To determine if HubP and PdeB swimming phenotypes are additive, we determined flagellum-mediated spreading in mutants lacking HubP, PdeB, or both (Fig.…”

“…We therefore hypothesized that other client proteins affecting flagellar functions might be directly or indirectly recruited by HubP. Accordingly, we recently identified another client protein, ZomB, which is crucial for inducing directional switches of the flagellar motor, that directly interacts with HubP and is to be destabilized in its absence (19).…”

Polar landmark protein HubP recruits flagella assembly protein FapA under glucose limitation in Vibrio vulnificus

“…Thus, we assumed that the motility defect of the hubP Δ(1777‐1951) mutant is unlikely to be associated with ParC. Another factor, ZomB, interacts directly with HubP in S. putrefaciens and V. parahaemolyticus , and its polar targeting and function are dependent on HubP (Brenzinger et al , ). However, little is known about which part of HubP is actually involved in the interaction with ZomB.…”