Heterogeneity of plant-associated streptococci as characterized by phenotypic features and restriction analysis of PCR-amplified 16S rDNA.

Thirty-five strains of streptococci isolated from forage grasses were examined by restriction analysis of PCR-amplified 16S rDNA. Using a set of seven endonucleases, five 16S rDNA genotypes were obtained. The isolates could be identified as belonging to the species Enterococcus faecium, Ent. mundtii, Ent. faecalis, Ent. casseliflavus and Lactococcus lactis ssp. lactis, respectively. To assign the isolates to one of these species, digestion with the endonuclease HinfI was sufficient. Data obtained from whole-cell protein analysis were in accordance with the species identification. Additionally, three of the five species found were subdivided into two related subgroups. Both methods are suitable for a rapid and unequivocal identification of plant-associated streptococci. The phenotypic characters showed a high diversity and were in some cases contrary to the expected features usually given in genus and species descriptions. The results demonstrated the close relatedness of the determined species in contrast to their high phenotypic heterogeneity.