Unknown,Transcriptomics,Genomics,Proteomics

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Next generation sequencing based transcriptomic analysis of bile stress response in Bifidobacterium longum BBMN68

ABSTRACT: Bifidobacterium longum is one of the natural inhabitants in human gastrointestinal tract. In order to colonize and exert particular functions in the gut, it has to be tolerant to the physiological concentrations of bile salts. In this work, we used RNA-Seq transcriptomics based on the Next-Generation Sequencing to investigate the global response to bile in B. longum BBMN68, a potential probiotic strain isolated from a healthy centenarian. In the presence of 0.75 g liter-1 ox-bile, the transcription of 236 genes were regulated (M-bM-^IM-% 3-fold, p < 0.001). Function analysis and Gene Ontology suggested that the bile stress response of B. longum BBMN68 covers almost all biological processes, including bile stress resistance, general stress response, central metabolic process, transmembrane transport, gene expression, cell proliferation and interaction with the host. Remarkably, 3 two-component systems and 11 transcription factors were up- or down-regulated by bile, and target genes of the regulators were identified by bacterial one-hybrid system and bioinformatics methods, resulting in a putative regulatory network that controls bile stress response in B. longum for the first time. This study significantly develops our understanding on bile stress response and brings new insight to the regulatory mechanism in bifidobateria. Whole mRNA profiles of B. longum BBMN68 growing in the absence (CK) and presence (OG) of ox-bile were generated using AB SOLiD technology and differentially expressed genes were anylyzed.

ORGANISM(S): Bifidobacterium longum

SUBMITTER: Haoran An

PROVIDER: E-GEOD-46446 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

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Next generation sequencing based transcriptomic analysis of bile stress response in Bifidobacterium longum BBMN68

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