Determination of 16S rRNA Sequences of Streptococcus mitis and Streptococcus gordonii and Phylogenetic Relationships among Members of the Genus Streptococcus

Abstract

We determined the 16s rRNA sequences of the type strains of Streptococcus mitis and Streptococcus gordonii and calculated the phylogenetic distances between those organisms and other members of the genus Streptococcus. The viridans group streptococci were separated into five phylogenetic groups; we named these groups the anginosus group, the mitis group, the salivarius group, the bovis group, and the mutans group. S. rnitis and S. gordonii clustered in the mitis group together with Streptococcus pneumoniae, Streptococcus oralis, Streptococcus sunguis, and Streptococcusparasanguis at levels of sequence homology of more than 96%. Within this group, S. mitis, S. om&, and S. pneumoniae exhibited more than 9% sequence homology with each other, although the DNA-DNA similarity values for their total chromosome DNAs were less than 60%.In the past 10 years, several new members have been added to the viridans streptococcus group (3, 11, 18-20). Streptococcus oralis, Streptococcus parasanguis, and Streptococcus gordonii are the major new species that have been described. These organisms are often isolated from human clinical specimens and thus are clinically important species. However, workers at clinical laboratories have found that it is difficult to identify viridans group streptococci because of the lack of decisive phenotypic characteristics.Some of the confusion concerning identification of these bacteria came from the type strain of Streptococcus mitis, strain NCTC 3165. This type strain had traits different from the traits described for the species. Therefore, Coykendall et al. ( 5 ) proposed that S. rnitis NCTC 3165 should be rejected as the type strain, and in Opinion 66 (10) strain NCTC 12261 was designated the neotype strain of S. rnitis. The rejected type strain is now identified as an S. gordonii strain, and we have confirmed this identification by DNA-DNA hybridization (unpublished data). In a previous study, we developed quantitative microplate DNA-DNA hybridization methods to identify streptococci (6, 7) and found that many strains which were identified as S. mitis, S. oralis, and Streptococcus sanguis by phenotypic methods were misidentified. Another problem arose when we applied quantitative DNA-DNA hybridization methods to the identification of viridans group streptococci. Many strains identified biochemically as S. mitis were difficult to differentiate from S. oralis and Streptococcus pneurnoniae even by the hybridization method because clinical strains NJ- 0.01 FIG. 1. Phylogenetic relationships among 34Streptococcus species. Distances were calculated by the neighbor-joining (NJ) method. S. pleomorphus was located far from other species, so its distance is indicated with an ellipsis; its true distance from the junction was 0.16944.

GyrB Polymorphisms Accurately Assign Invasive Viridans Group Streptococcal Species

“…16S gene sequencing is the most widely used single-gene approach for determining bacterial species, but previous investigations have shown its limited utility for classifying VGS strains, particularly those of the S. mitis and S. oralis species (7,8,33). However, these are the two predominant VGS species isolated from oncology patients (2, 4-6).…”

“…The full-length 16S gene was sequenced using the universal primers 8F and 1492R, as previously described (29,33,34). The region of the 16S gene used for phylogenetic analyses and species identification was nucleotides 50 to 1457, due to ambiguous reads at the 5= and 3= ends for a small number of strains.…”

Genomic insights that advance the species definition for prokaryotes

“…DNA-DNA reassociation values between species were obtained from the literature (11,(14)(15)(16)(17)(18). When the sequenced strains were the same as the ones used in the DNA-DNA reassociation experiments, we directly compared the DNA-DNA reassociation values with the ANI of the sequenced genomes.…”

A Genome-Wide Profiling Strategy as an Aid for Searching Unique Identification Biomarkers for Streptococcus

“…The full length sequence of rrs of Streptococcus spp. : S. pneumoniae, S. pseudopneumoniae, S. mitis, and S. oralis show more than 99 % similarity leading to unsuccessful or misleading results [10]. Recent studies have elucidated certain latent but unique characteristics in rrs: (1) 30-50 nucleotides (nts) long signatures, and (2) restriction endonuclease (RE) digestion patterns [12][13][14][15][16].…”