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

Stuti K. Desai, Krithi Nandimath, S. Mahadevan

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Utilization of the aryl-β-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-β-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-β- 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 β-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-β-glucosidase B encoded by the silent asc operon. BglF function is needed since AscF is unable to transport β-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.

Original languageEnglish (US)
Pages (from-to)821-833
Number of pages13
JournalArchives of Microbiology
Issue number10
StatePublished - Oct 2010
Externally publishedYes


  • Beta-glucosides
  • Silent genes
  • Transcriptional activation

ASJC Scopus subject areas

  • Microbiology
  • Biochemistry
  • Molecular Biology
  • Genetics


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