The global regulators ArcA and CytR collaboratively modulate Vibrio cholerae motility

Abstract

Background Vibrio cholerae, a Gram-negative bacterium, is highly motile owing to the presence of a single polar flagellum. The global anaerobiosis response regulator, ArcA regulates the expression of virulence factors and enhance biofilm formation in V. cholerae. However, the function of ArcA for the motility of V. cholerae is yet to be elucidated. CytR, which represses nucleoside uptake and catabolism, is known to play a chief role in V. cholerae pathogenesis and flagellar synthesis but the mechanism that CytR influences motility is unclear. Results In this study, we found that the ΔarcA mutant strain exhibited higher motility than the WT strain due to ArcA directly repressed flrA expression. We further discovered that CytR directly enhanced fliK expression, which explained why the ΔcytR mutant strain was retarded in motility. On the other hand, cytR was a direct ArcA target and cytR expression was directly repressed by ArcA. As expected, cytR expression was down-regulated. Conclusions Overall, ArcA plays a critical role in V. cholerae motility by regulating flrA expression directly and fliK indirectly in the manner of cytR.

The regulatory network comprising ArcAB‐RpoS‐RssB influences motility in Vibrio cholerae

“…For example, over 1100 E. coli genes are regulated directly or indirectly by ArcA (Salmon et al, 2005). ArcA also acts as a global regulator in V. cholerae, affecting virulence, biofilm formation and motility (Li et al, 2022;Sengupta et al, 2003;Xi et al, 2020;Zhou et al, 2021).…”

“…The arcA-knockout mutant exhibited a hypomotile phenotype under nutrient-poor conditions. Due to the derepression of rpoS transcription in the arcA-knockout mutant (see above) and previous experiments byLi et al (2022), showing an increase in the motility phenotype of the ΔarcA mutant, caused by the repression of flrA transcription by ArcA, a hypermotile phenotype was expected. FlrA is the master regulator of flagella biosynthesis and part of the Class I flagella transcription hierarchy.…”

“…The discrepancy to the study of Li and colleagues may be attributed to several factors as follows: firstly, derepressed rpoS transcription may not automatically lead to more RpoS protein in the cell, which subsequently induces the transcription of motilityand chemotaxis-related genes. Secondly,Li et al (2022) used different conditions, namely LB medium-based swarming agar plates, from the conditions used by us to determine motility behaviour.…”

Nocturnal Acidification: A Coordinating Cue in the Euprymna scolopes–Vibrio fischeri Symbiosis

“…Such loss of flagellar gene expression has been observed among diverse bacteria that are tightly packed in tissues (similar to the condition of the light organ at night, when V. fischeri symbionts are at high cell density) [ 95 ]. Flagellar gene expression is known to be repressed by several of the regulators of quorum-sensing and luminescence production (LitR represses flagellin genes, as does AinS [ 96 ]), as well as environmental stress response regulators (in V. cholera , ArcA represses flagellar gene expression and represses CytR (the negative regulator of competence, which is repressed by free environmental DNA and nucleosides) [ 97 ]). Somewhat surprisingly, symbiont transcriptome data has revealed that expression of flagellar structural genes is upregulated several hours before venting at dawn [ 85 , 95 ].…”

RpoN is required for the motility and contributes to the killing ability of Plesiomonas shigelloides

“…The procedures of the lux reporter assay were described in a previous study [ 84 ]. The amplification products of the respective promoter regions were digested and cloned into the XhoI-BamHI site, upstream of the lux genes, in the plasmid pMS402.…”