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Diverse pathways for salicin utilization in Shigella sonnei and Escherichia coli carrying an impaired bgl operon

Desai, Stuti K and Nandimath, Krithi and Mahadevan, S (2010) Diverse pathways for salicin utilization in Shigella sonnei and Escherichia coli carrying an impaired bgl operon. In: Archives of Microbiology, 192 (10). pp. 821-833.

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Utilization of the aryl-beta-glucosides salicin or arbutin in most wild-type strains of E. coli is achieved by a single-step mutational activation of the bgl operon. Shigella sonnei, a branch of the diverse E. coli strain tree, requires two sequential mutational steps for achieving salicin utilization as the bglB gene, encoding the phospho-beta-glucosidase B, harbors an inactivating insertion. We show that in a natural isolate of S. sonnei, transcriptional activation of the gene SSO1595, encoding a phospho-beta-glucosidase, enables salicin utilization with the permease function being provided by the activated bgl operon. SSO1595 is absent in most commensal strains of E. coli, but is present in extra-intestinal pathogens as bgcA, a component of the bgc operon that enables beta-glucoside utilization at low temperature. Salicin utilization in an E. coli bglB laboratory strain also requires a two-step activation process leading to expression of BglF, the PTS-associated permease encoded by the bgl operon and AscB, the phospho-beta-glucosidase B encoded by the silent asc operon. BglF function is needed since AscF is unable to transport beta-glucosides as it lacks the IIA domain involved in phopho-relay. Activation of the asc operon in the Sal(+) mutant is by a promoter-up mutation and the activated operon is subject to induction. The pathway to achieve salicin utilization is therefore diverse in these two evolutionarily related organisms; however, both show cooperation between two silent genetic systems to achieve a new metabolic capability under selection.

Item Type: Journal Article
Publication: Archives of Microbiology
Publisher: Springer
Additional Information: Copyright of this article belongs to Springer.
Keywords: Silent genes; Beta-glucosides; Transcriptional activation.
Department/Centre: Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited: 27 Oct 2010 06:48
Last Modified: 27 Oct 2010 06:48
URI: http://eprints.iisc.ac.in/id/eprint/33455

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