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Applied and Environmental Microbiology, April 2009, p. 2284-2293, Vol. 75, No. 8
0099-2240/09/$08.00+0     doi:10.1128/AEM.02621-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Characterization of a β-Glucoside Operon (bgc) Prevalent in Septicemic and Uropathogenic Escherichia coli Strains{triangledown} ,{dagger}

Girish Neelakanta,{ddagger} T. Sabari Sankar, and Karin Schnetz*

Institute for Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany

Received 17 November 2008/ Accepted 10 February 2009

Escherichia coli strains, in general, do not ferment cellobiose and aryl-β-D-glucosidic sugars, although "cryptic" β-D-glucoside systems have been characterized. Here we describe an additional cryptic operon (bgc) for the utilization of cellobiose and the aryl-β-D-glucosides arbutin and salicin at low temperature. The bgc operon was identified by the characterization of β-glucoside-positive mutants of an E. coli septicemia strain (i484) in which the well-studied bgl (aryl-β-D-glucoside) operon was deleted. These bgc* mutants appeared after 5 days of incubation on salicin indicator plates at 28°C. The bgc operon codes for proteins homologous to β-glucoside/cellobiose-specific phosphoenolpyruvate-dependent phosphotransfer system permease subunits IIB (BgcE), IIC (BgcF), and IIA (BgcI); a porin (BgcH); and a phospho-β-D-glucosidase (BgcA). Next to the bgc operon maps the divergent bgcR gene, which encodes a GntR-type transcriptional regulator. Expression of the bgc operon is dependent on the cyclic-AMP-dependent regulator protein CRP and positively controlled by BgcR. In the bgc* mutants, a single nucleotide exchange enhances the activity of the bgc promoter, rendering it BgcR independent. Typing of a representative collection of E. coli demonstrated the prevalence of bgc in strains of phylogenetic group B2, representing mainly extraintestinal pathogens, while it is rare among commensal E. coli strains. The bgc locus is also present in the closely related species Escherichia albertii. Further, bioinformatic analyses demonstrated that homologs of the bgc genes exist in the enterobacterial Klebsiella, Enterobacter, and Citrobacter spp. and also in gram-positive bacteria, indicative of horizontal gene transfer events.

* Corresponding author. Mailing address: Institute for Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany. Phone: 49-221-4703815. Fax: 49-221-4705185. E-mail: schnetz{at}uni-koeln.de

{triangledown} Published ahead of print on 20 February 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

{ddagger} Present address: Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06520.

Applied and Environmental Microbiology, April 2009, p. 2284-2293, Vol. 75, No. 8
0099-2240/09/$08.00+0     doi:10.1128/AEM.02621-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Ishida, Y., Kori, A., Ishihama, A. (2009). Participation of Regulator AscG of the {beta}-Glucoside Utilization Operon in Regulation of the Propionate Catabolism Operon. J. Bacteriol. 191: 6136-6144 [Abstract] [Full Text]  


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