Identification and Characterization of VC1123, a Novel Gene Required for Colonization in Vibrio cholerae

Xiuping Fu¹Xinyu Wen²Yuanyuan Yang¹Weili Liang¹Bo Pang¹XU LI²Baowei Diao¹Jie Li¹Jingyun Zhang^1*Biao Kan^1*

• ¹National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
• ²School of Light Industry Science and Engineering, Beijing Technology and Business University, Beijng, China

A novel lineage of serogroup O1 El Tor Vibrio cholerae, genetically distinct from the seventh-pandemic strain, has recently emerged in China and been linked to diarrheal outbreaks. To identify potential virulence-associated determinants, we compared the transcriptomes of two new-lineage isolates—VC6050 (ctxAB⁺) and VC6055 (ctxAB⁻)—alongside the seventh-pandemic strain N16961 (ctxAB⁺), following growth in virulence-inducing (AKI) and non-inducing (LB) media. Focusing specifically on the comparison between the toxigenic new-lineage strain VC6050 and the classical pandemic strain N16961 under AKI conditions, VC6050 displayed more pronounced repression of chemotaxis-and biofilm-related genes than N16961. We hypothesize that this enhanced downregulation may reflect an evolved strategy to minimize host immune detection or phage predation. Among genes highly expressed across all three strains in AKI, VC1123 was selected for functional characterization. Targeted deletion of VC1123 in N16961 resulted in a markedly enhanced colonization capacity in the neonatal mouse intestine, which was fully restored upon genetic complementation. To dissect the molecular basis of this enhanced colonization phenotype, we performed comparative RNA-seq on wild-type and ΔVC1123 strains grown in LB medium. Deletion of VC1123 led to marked upregulation of the outer membrane porin gene ompU and concomitant downregulation of ompT, without altering expression of the master regulators toxR or toxS. Given that OmpU and OmpT—classically controlled by the ToxR/ToxS system—exert opposing effects on intestinal fitness (OmpU enhances bile resistance, adhesion, and survival; OmpT compromises gut colonization), these transcriptional shifts provide a plausible explanation for the observed phenotype. Collectively, our findings indicate that VC1123 constrains intestinal colonization in V. cholerae, likely by modulating ompU and ompT expression via a ToxR/ToxS-independent pathway. This work uncovers a previously under-explored layer of virulence control mediated by a conserved gene of unknown function.