Research Article  Contribution of Exogenous Genetic Elements to
the Group A Streptococcus Metagenome    • Stephen B. Beres,
• James M. Musser mail      To whom correspondence should be
addressed. E-mail:     • Published: August 29, 2007   • DOI:
10.1371/journal.pone.0000800   • Published in PLOS ONE
Variation in gene content among strains of a bacterial species
contributes to biomedically relevant differences in phenotypes
such as virulence and antimicrobial resistance. Group A
Streptococcus (GAS) causes a diverse array of human infections
and sequelae, and exhibits a complex pathogenic behavior. To
enhance our understanding of genotype-phenotype relationships in
this important pathogen, we determined the complete genome
sequences of four GAS strains expressing M protein serotypes
(M2, M4, and 2 M12) that commonly cause noninvasive and invasive
infections. These sequences were compared with eight previously
determined GAS genomes and regions of variably present gene
content were assessed. Consistent wit