Fur Represses Vibrio cholerae Biofilm Formation via Direct Regulation of vieSAB, cdgD, vpsU, and vpsA-K Transcription

• Published in: Frontiers in microbiology 2020-10, Vol.11, p.587159-587159
• Main Authors: Gao, He, Ma, Lizhi, Qin, Qin, Qiu, Yue, Zhang, Jingyun, Li, Jie, Lou, Jing, Diao, Baowei, Zhao, Hongqun, Shi, Qiannan, Zhang, Yiquan, Kan, Biao
• Format: Article
• Language: English
• Subjects: biofilm; c-di-GMP; Fur; Microbiology; Vibrio cholerae; vps
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2020.587159

Attached Vibrio cholerae biofilms are essential for environmental persistence and infectivity. The vps loci ( vpsU , vpsA -K, and vpsL-Q ) are required for mature biofilm formation and are responsible for the synthesis of exopolysaccharide. Transcription of vps genes is activated by the signaling molecule bis-(3′–5′)-cyclic di-GMP (c-di-GMP), whose metabolism is controlled by the proteins containing the GGDEF and/or EAL domains. The ferric uptake regulator (Fur) plays key roles in the transcription of many genes involved in iron metabolism and non-iron functions. However, roles for Fur in Vibrio biofilm production have not been documented. In this study, phenotypic assays demonstrated that Fur, independent of iron, decreases in vivo c-di-GMP levels and inhibits in vitro biofilm formation by Vibrio cholerae . The Fur box-like sequences were detected within the promoter-proximal DNA regions of vpsU , vpsA-K , vieSAB , and cdgD , suggesting that transcription of these genes may be under the direct control of Fur. Indeed, the results of luminescence, quantitative PCR (qPCR), electrophoretic mobility shift assay (EMSA), and DNase I footprinting assays demonstrated Fur to bind to the promoter-proximal DNA regions of vpsU , vpsA-K , and cdgD to repress their transcription. In contrast, Fur activates the transcription of vieSAB in a direct manner. The cdgD and vieSAB encode proteins with GGDEF and EAL domains, respectively. Thus, data presented here highlight a new physiological role for Fur wherein it acts as a repressor of V. cholerae biofilm formation mediated by decreasing the production of exopolysaccharide and the intracellular levels of c-di-GMP.