Open AccessVpsR Directly Activates Transcription of Multiple Biofilm Genes in Vibrio cholerae
Author(s) -
Meng-Lun Hsieh,
Christopher M. Waters,
Deborah M. Hinton
Publication year - 2020
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00234-20
Subject(s) - vibrio cholerae , biology , biofilm , operon , transcription (linguistics) , rna polymerase , activator (genetics) , rna polymerase ii , microbiology and biotechnology , gene , biogenesis , cholera toxin , promoter , rna , genetics , bacteria , gene expression , mutant , linguistics , philosophy
Vibrio cholerae biofilm biogenesis, which is important for survival, dissemination, and persistence, requires multiple genes in the Vibrio polysaccharides ( vps ) operons I and II as well as the cluster of ribomatrix ( rbm ) genes. Transcriptional control of these genes is a complex process that requires several activators/repressors and the ubiquitous signaling molecule, cyclic di-GMP (c-di-GMP). Previously, we demonstrated that VpsR directly activates RNA polymerase containing σ 70 (σ 70 -RNAP) at the vpsL promoter (P vpsL ), which precedes the vps -II operon, in a c-di-GMP-dependent manner by stimulating formation of the transcriptionally active, open complex. Using in vitro transcription, electrophoretic mobility shift assays, and DNase I footprinting, we show here that VpsR also directly activates σ 70 -RNAP transcription from other promoters within the biofilm formation cluster, including P vpsU , at the beginning of the vps -I operon, P rbmA , at the start of the rbm cluster, and P rbmF , which lies upstream of the divergent rbmF and rbmE genes. In this capacity, we find that VpsR is able to behave both as a class II activator, which functions immediately adjacent/overlapping the core promoter sequence (P vpsL and P vpsU ), and as a class I activator, which functions farther upstream (P rbmA and P rbmF ). Because these promoters vary in VpsR-DNA binding affinity in the absence and presence of c-di-GMP, we speculate that VpsR's mechanism of activation is dependent on both the concentration of VpsR and the level of c-di-GMP to increase transcription, resulting in finely tuned regulation. IMPORTANCE Vibrio cholerae , the bacterial pathogen that is responsible for the disease cholera, uses biofilms to aid in survival, dissemination, and persistence. VpsR, which directly senses the second messenger c-di-GMP, is a major regulator of this process. Together with c-di-GMP, VpsR directly activates transcription by RNA polymerase containing σ 70 from the vpsL biofilm biogenesis promoter. Using biochemical methods, we demonstrate for the first time that VpsR/c-di-GMP directly activates σ 70 -RNA polymerase at the first genes of the vps and ribomatrix operons. In this regard, it functions as either a class I or class II activator. Our results broaden the mechanism of c-di-GMP-dependent transcription activation and the specific role of VpsR in biofilm formation.