Dataset Information

The bile response repressor BreR regulates expression of the Vibrio cholerae breAB efflux system operon.

ABSTRACT: Enteric pathogens have developed several resistance mechanisms to survive the antimicrobial action of bile. We investigated the transcriptional profile of Vibrio cholerae O1 El Tor strain C6706 under virulence gene-inducing conditions in the presence and absence of bile. Microarray analysis revealed that the expression of 119 genes was affected by bile. The mRNA levels of genes encoding proteins involved in transport were increased in the presence of bile, whereas the mRNA levels of genes encoding proteins involved in pathogenesis and chemotaxis were decreased. This study identified genes encoding transcriptional regulators from the TetR family (vexR and breR) and multidrug efflux pumps from the resistance-nodulation-cell division superfamily (vexB and vexD [herein renamed breB]) that were induced in response to bile. Further analysis regarding vexAB and breAB expression in the presence of various antimicrobial compounds established that vexAB was induced in the presence of bile, sodium dodecyl sulfate, or novobiocin and that the induction of breAB was specific to bile. BreR is a direct repressor of the breAB promoter and is able to regulate its own expression, as demonstrated by transcriptional and electrophoretic mobility shift assays (EMSA). The expression of breR and breAB is induced in the presence of the bile salts cholate, deoxycholate, and chenodeoxycholate, and EMSA showed that deoxycholate is able to abolish the formation of BreR-P(breR) complexes. We propose that deoxycholate is able to interact with BreR and induce a conformational change that interferes with the DNA binding ability of BreR, resulting in breAB and breR expression. These results provide new insight into a transcriptional regulator and a transport system that likely play essential roles in the ability of V. cholerae to resist the action of bile in the host.

SUBMITTER: Cerda-Maira FA

PROVIDER: S-EPMC2576662 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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The bile response repressor BreR regulates expression of the Vibrio cholerae breAB efflux system operon.

Cerda-Maira Francisca A FA Ringelberg Carol S CS Taylor Ronald K RK

Journal of bacteriology 20080905 22

Enteric pathogens have developed several resistance mechanisms to survive the antimicrobial action of bile. We investigated the transcriptional profile of Vibrio cholerae O1 El Tor strain C6706 under virulence gene-inducing conditions in the presence and absence of bile. Microarray analysis revealed that the expression of 119 genes was affected by bile. The mRNA levels of genes encoding proteins involved in transport were increased in the presence of bile, whereas the mRNA levels of genes encodi ...[more]

PMID: 18776020

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Project description:Enteric pathogens have developed several resistance mechanisms to survive the antimicrobial action of bile. We investigated the transcriptional profile of Vibrio cholerae O1 El Tor strain C6706 under virulence gene inducing conditions, in the presence and absence of bile. Microarray analysis revealed that the expression of 119 genes was affected by bile. The mRNA levels of genes encoding proteins involved in transport was increased in the presence of bile, whereas mRNA levels of genes encoding proteins involved in pathogenesis and chemotaxis was decreased. This study identified genes encoding transcriptional regulators from the TetR family (vexR and breR) and multidrug efflux pumps from the RND superfamily (vexB and vexD [here renamed breB]) that were induced in response to bile. Further analysis regarding vexAB and breAB expression in the presence of various antimicrobial compounds established that vexAB was induced in the presence of bile, SDS or novobiocin, whereas induction of breAB was specific to bile. BreR is a direct repressor of the breAB promoter and is able to autoregulate its own expression, as demonstrated by transcriptional and electrophoretic mobility shift assays (EMSA). Expression of breR and breAB is induced in the presence of the bile salts cholate, deoxycholate or chenodeoxycholate and EMSA showed that deoxycholate is able to abolish formation of BreR-PbreR complexes. We propose that deoxycholate is able to interact with BreR and induce a conformational change that will interfere with its DNA binding ability resulting in breAB and breR expression. These results provide new insight into a transcriptional regulator and a transport system that likely play an essential role in the ability of Vibrio cholerae to resist the action of bile in the host. Keywords: Vibrio cholerae response to bile Three independent experiments were performed for the microarray analysis. From each experiment, RNA was obtained from four different time points and was prepared for hybridization, therefore, a total of 3 slides were analyzed per time point. The growth conditions were as follows; C6706 str2 was grown 15 h in LB medium at 30 degrees C with aeration. The cultures were then diluted 100-fold into AKI medium with, or without, 0.4% crude bile (high bile concentration) and were grown at 37degrees C for 3.5 h stationary followed by 2 h with aeration to induce virulence gene expression. Then the cultures were diluted 100-fold into AKI medium with, or without, 0.02% crude bile (low bile concentration) and were grown at 37 degrees C for 2 h stationary. Samples were obtained from 4 different time points: 2, 4, and 5.5 h from the high bile cultures, and at 2 h from the low bile cultures.

Dataset Information

The bile response repressor BreR regulates expression of the Vibrio cholerae breAB efflux system operon.

Publications

The bile response repressor BreR regulates expression of the Vibrio cholerae breAB efflux system operon.

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