Nucleic acid hybridization and cell wall composition studies of pyogenic streptococci

DNA‐rRNA and DNA‐DNA hybridization studies indicate that the classical pyogenic streptococci can be divided into five homology clusters. Based on these studies the term pyogenic streptococci should be confined to the first cluster consisting of serological groups A, A‐variant, C, G (‘large’ colony, type II) and L. Streptococci of serological groups B and M form the second cluster. The third cluster is composed of streptococci of serological groups R and S and serological groups U, V and P are found in the fourth cluster. The fifth cluster comprises strains of Streptococcus anginosus S. intermedius, Streptococcus MG and serological groups G (‘minute’ colony, type I) and F (type I). Most of the test strains contain the peptidoglycan type Lys‐Ala1–3. Only streptococci of serogroups R and S reveal a directly cross‐linked peptidoglycan. Rhamnose was found as characteristic component of all cell wall polysaccharides. The impact of our results on the systematics of classical pyogenic streptococci will be discussed.