Evolutionary Origin and Emergence of a Highly Successful Clone of Serotype M1 Group A Streptococcus Involved Multiple Horizontal Gene Transfer Events.
Sumby, Paul 1,2; Porcella, Steve F. 1; Madrigal, Andres G. 1,a; Barbian, Kent D. 1; Virtaneva, Kimmo 1; Ricklefs, Stacy M. 1; Sturdevant, Daniel E. 1; Graham, Morag R. 1,a; Vuopio-Varkila, Jaana 3; Hoe, Nancy P. 1; Musser, James M. 1,2
[Article] Journal of Infectious Diseases. 192(5):771-782, September 1, 2005.

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: To better understand the molecular events involved in the origin of new pathogenic bacteria, we studied the evolution of a highly virulent clone of serotype M1 group A Streptococcus (GAS). Genomic, DNA-DNA microarray, and single-nucleotide polymorphism analyses indicated that this clone evolved through a series of horizontal gene transfer events that involved (1) the acquisition of prophages encoding streptococcal pyrogenic exotoxin A and extracellular DNases and (2) the reciprocal recombination of a 36-kb chromosomal region encoding the extracellular toxins NAD -glycohydrolase (NADase) and streptolysin O (SLO). These gene transfer events were associated with significantly increased production of SLO and NADase. Virtual identity in the 36-kb region present in contemporary serotype M1 and M12 isolates suggests that a serotype M12 strain served as the donor of this region. Multiple horizontal gene transfer events were a crucial factor in the evolutionary origin and emergence of a very abundant contemporary clone of serotype M1 GAS

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