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Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance.

ABSTRACT: Bifidobacteria are normal inhabitants of the human gut. Some strains of this genus are considered health promoting or probiotic, being included in numerous food products. In order to exert their health benefits, these bacteria must overcome biological barriers, including bile salts, to colonize and survive in specific parts of the intestinal tract. The role of multidrug resistance (MDR) transporters in bile resistance of probiotic bacteria and the effect of bile on probiotic gene expression are not fully understood. In the present study, the effect of subinhibitory concentrations of bile on the expression levels of predicted MDR genes from three different bifidobacterial strains, belonging to Bifidobacterium longum subsp. longum, Bifidobacterium breve, and Bifidobacterium animalis subsp. lactis, was tested. In this way, two putative MDR genes whose expression was induced by bile, BL0920 from B. longum and its homolog, Bbr0838, from B. breve, were identified. The expression of the BL0920 gene in Escherichia coli was shown to confer resistance to bile, likely to be mediated by active efflux from the cells. To the best of our knowledge, this represents the first identified bifidobacterial bile efflux pump whose expression is induced by bile.

SUBMITTER: Gueimonde M

PROVIDER: S-EPMC2681658 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance.

Gueimonde Miguel M Garrigues Christel C van Sinderen Douwe D de los Reyes-Gavilán Clara G CG Margolles Abelardo A

Applied and environmental microbiology 20090320 10

Bifidobacteria are normal inhabitants of the human gut. Some strains of this genus are considered health promoting or probiotic, being included in numerous food products. In order to exert their health benefits, these bacteria must overcome biological barriers, including bile salts, to colonize and survive in specific parts of the intestinal tract. The role of multidrug resistance (MDR) transporters in bile resistance of probiotic bacteria and the effect of bile on probiotic gene expression are ...[more]

PMID: 19304838

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Project description:Bacterial promoters consist of core sequence motifs termed -35 and -10 boxes. The consensus motifs are TTGACA and TATAAT, respectively, which were identified from leading investigations on Escherichia coli However, the consensus sequences are not likely to fit genetically divergent bacteria. The sigma factor of the genus Bifidobacterium has a characteristic polar domain in the N terminus, suggesting the possibility of specific promoter recognition. We reevaluated the structure of Bifidobacterium longum NCC2705 promoters and compared them to other bacteria. Transcriptional start sites (TSSs) of the B. longum NCC2705 strain were identified using transcriptome sequencing (RNA-Seq) analysis to extract promoter regions. Conserved motifs of a bifidobacterial promoter were determined using regions upstream of TSSs and a hidden Markov model. As a result, consensus motifs of the -35 and -10 boxes were TTGTGC and TACAAT, respectively. To assess each base of both motifs, we constructed 37 plasmids based on pKO403-TPCTcon, including the hup promoter connected with a chloramphenicol acetyltransferase as a reporter gene. This reporter assay showed two optimal motifs of the -35 and -10 boxes, namely, TTGNNN and TANNNT, respectively. We further analyzed spacer lengths between the -35 and -10 boxes via a bioinformatics approach. The spacer lengths predominant in bacteria have been generally reported to be approximately 17 bp. In contrast, the predominant spacer lengths in the genus Bifidobacterium and related species were 11 bp, in addition to 17 bp. A reporter assay to assess the spacer lengths indicated that the 11-bp spacer length produced unusually high activity.IMPORTANCE The structures of sigma factors vary among bacterial strains, indicating that recognition rules may also vary. Therefore, we investigated the promoter structure of Bifidobacterium longum NCC2705 using a bioinformatics approach and wet analyses. The most frequent and optimal motifs were similar to other bacterial consensus motifs. The optimal spacer length between the two boxes was reported to be 17 bp. It is widely applied to a bioinformatics approach for other bacteria. Unexpectedly, conserved spacer lengths were 11 bp as well as 17 bp in the genus Bifidobacterium Moreover, the sigma factor of the genus Bifidobacterium has a characteristic domain in the N terminus which may contribute to the additional functions. Hence, it would be valuable to reevaluate the promoter in other organisms.

Dataset Information

Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance.

Publications

Bile-inducible efflux transporter from Bifidobacterium longum NCC2705, conferring bile resistance.

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