Streptococcus is a diverse genus of bacteria containing over 50 species, some notable as clinically relevant pathogens. Species in the Group A classification, with S. pyogenes as a defining member, cause infections in the skin and throat, such as cellulitis, impetiigo, and strep throat. Infection by group B streptococcus, or S. agalactiae, during pregnancy can prematurely rupture prenatal membranes and cause infection in the newborn. S. pneumonia is a main cause of community acquired pneumonia and meningitis, as well as other pneumococcal infections. Streptococcus species are gram-positive, cocci, and have genomes ranging from 1.8 to 2.3 Mb.