AUTHOR=Salvadori Gabriela , Junges Roger , Morrison Donald A. , Petersen Fernanda C. 

TITLE=Competence in Streptococcus pneumoniae and Close Commensal Relatives: Mechanisms and Implications

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2019.00094

DOI=10.3389/fcimb.2019.00094

ISSN=2235-2988

ABSTRACT=<p>The mitis group of streptococci comprises species that are common colonizers of the naso-oral-pharyngeal tract of humans. <italic>Streptococcus pneumoniae</italic> and <italic>Streptococcus mitis</italic> are close relatives and share ~60–80% of orthologous genes, but still present striking differences in pathogenic potential toward the human host. <italic>S. mitis</italic> has long been recognized as a reservoir of antibiotic resistance genes for <italic>S. pneumoniae</italic>, as well as a source for capsule polysaccharide variation, leading to resistance and vaccine escape. Both species share the ability to become naturally competent, and in this context, competence-associated killing mechanisms such as fratricide are thought to play an important role in interspecies gene exchange. Here, we explore the general mechanism of natural genetic transformation in the two species and touch upon the fundamental clinical and evolutionary implications of sharing similar competence, fratricide mechanisms, and a large fraction of their genomic DNA.</p>