A taxonomic study of the genus Streptococcus.
thesisposted on 19.11.2015, 09:11 by Paul Dennis. Bridge
Two-hundred and two strains of streptococci and related organisms were used in a numerical taxonomy. Ten major phenons containing twenty-seven subphenons and one loosely linked subphenon were found using Gower's coefficient and UPGMA methods. The Simple Matching coefficient and the Pattern difference were also used and these gave findings in broad agreement with those from Gower's coefficient. Nine of the ten phenons contained streptococci, the tenth containing representatives of Leuconostoc and Gemella. Strains of Pediococcus appeared only distantly related to the streptococci, clustering as the loosely linked subphenon. Overlap statistics were performed on the subphenons and with few exceptions they proved distinct. An identification matrix was made from the taxonomy and tested. This matrix was also used to construct a further dendrogram, based solely on the sixty characters in the matrix. This dendrogram was similar to those seen earlier. A further identification matrix was constructed using both tests from this study and from the literature. Both of the matrices were tested for overlap, the matrix based solely on this study giving more distinct groups. Further work was undertaken on representative strains from the subphenons. This involved the determination of DNA base ratios, detection of esterases in polyacrylamide gels and the numerical analysis of protein traces in polyacrylamide gels. This further work failed to group any of the organisms at anything other than species level. However, the results did not directly contradict the numerical taxonomy, and the groups from this were retained. These groups consisted of eight species-groups. These were, enterococci, viridans, pyogenic, para-viridans, para-pyogenic, S. thermophilus, S. pneumoniae and lactic. The strains received as aerococci did not form a distinct cluster within the numerical taxonomy and did not appear different from the streptococci in the other work. They showed properties similar to both Streptococcus and Pediococcus and may be intermediate between the two genera.