The genus can be further branched into 40 species, which all have the abovementioned characteristics, but they differ in details. Most famous is S. pyogenes. Most Streptococci are pathogenic which means they can cause disease. Streptococcus pyogenes causes sore throat and scarlet fever, sometimes more dangerous diseases. Their nickname is 'flesh-eating bacteria', but this serious disease is not common.
Many people carry streptococci in their mouth and throat without complaints.
Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.