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Journal of Bacteriology, April 2009, p. 2257-2265, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01624-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Novel Integrative Conjugative Element Mediates Genetic Transfer from Group G Streptococcus to Other β-Hemolytic Streptococci{triangledown}

Mark R. Davies,1,2,3,{dagger} Josephine Shera,1 Gary H. Van Domselaar,4,5 Kadaba S. Sriprakash,1,2,3,6 and David J. McMillan1,2,6*

Bacterial Pathogenesis Laboratory, The Queensland Institute of Medical Research, Brisbane 4029, Queensland, Australia,1 The Australian Centre for International Tropical Health and Nutrition, The Queensland Institute of Medical Research, Brisbane 4029, Queensland, Australia,2 Cooperative Research Centre for Vaccine Technology, The Queensland Institute of Medical Research, Brisbane 4029, Queensland, Australia,3 National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba R3E 3R2, Canada,4 Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada,5 Griffith Medical Research College, Herston, Queensland, Australia6

Received 14 November 2008/ Accepted 13 January 2009

Lateral gene transfer is a significant contributor to the ongoing evolution of many bacterial pathogens, including β-hemolytic streptococci. Here we provide the first characterization of a novel integrative conjugative element (ICE), ICESde3396, from Streptococcus dysgalactiae subsp. equisimilis (group G streptococcus [GGS]), a bacterium commonly found in the throat and skin of humans. ICESde3396 is 64 kb in size and encodes 66 putative open reading frames. ICESde3396 shares 38 open reading frames with a putative ICE from Streptococcus agalactiae (group B streptococcus [GBS]), ICESa2603. In addition to genes involves in conjugal processes, ICESde3396 also carries genes predicted to be involved in virulence and resistance to various metals. A major feature of ICESde3396 differentiating it from ICESa2603 is the presence of an 18-kb internal recombinogenic region containing four unique gene clusters, which appear to have been acquired from streptococcal and nonstreptococcal bacterial species. The four clusters include two cadmium resistance operons, an arsenic resistance operon, and genes with orthologues in a group A streptococcus (GAS) prophage. Streptococci that naturally harbor ICESde3396 have increased resistance to cadmium and arsenate, indicating the functionality of genes present in the 18-kb recombinogenic region. By marking ICESde3396 with a kanamycin resistance gene, we demonstrate that the ICE is transferable to other GGS isolates as well as GBS and GAS. To investigate the presence of the ICE in clinical streptococcal isolates, we screened 69 isolates (30 GGS, 19 GBS, and 20 GAS isolates) for the presence of three separate regions of ICESde3396. Eleven isolates possessed all three regions, suggesting they harbored ICESde3396-like elements. Another four isolates possessed ICESa2603-like elements. We propose that ICESde3396 is a mobile genetic element that is capable of acquiring DNA from multiple bacterial sources and is a vehicle for dissemination of this DNA through the wider β-hemolytic streptococcal population.

* Corresponding author. Mailing address: Bacterial Pathogenesis Laboratory, Queensland Institute of Medical Research, Brisbane, Qld 4006, Australia. Phone: 61-7-38453698. Fax: 61-7-38453507. E-mail: david.mcmillan{at}qimr.edu.au

{triangledown} Published ahead of print on 23 January 2009.

{dagger} Present address: Centre for Immunology and Infection, Department of Biology, University of York and Hull York Medical School, YO10 5YW, United Kingdom.

Journal of Bacteriology, April 2009, p. 2257-2265, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01624-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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