Summary auto-generated
This study evaluated the 600 base pair hsp60 gene as a molecular marker for identifying and determining evolutionary relationships among Staphylococcus and Macrococcus species. Researchers PCR-amplified and sequenced partial hsp60 genes from 40 validly described Staphylococcus species or subspecies and four Macrococcus species, then constructed phylogenetic trees using neighbor-joining analysis. Results demonstrated excellent concordance with phylogenetic trees based on 16S rRNA gene sequences and current taxonomic classifications. The hsp60 gene effectively separated Macrococcus from Staphylococcus and revealed five major subdivisions within Staphylococcus corresponding to recognized groups: aureus, epidermidis, haemolyticus, saprophyticus, and intermedius groups. Notably, Macrococcus clustered near the cytochrome c oxidase-positive sciuri group of staphylococci, suggesting evolutionary relatedness. Pairwise sequence comparisons showed hsp60 sequences were more divergent and discriminatory than 16S rRNA sequences for species differentiation, with identity scores ranging from 74-98% among Staphylococcus species versus higher 16S rRNA percentages. The study concluded that hsp60 gene sequencing represents a useful alternative molecular tool for accurate taxonomic classification and phylogenetic analysis of these clinically important bacterial genera.
Key findings
- The partial hsp60 gene is more discriminatory than 16S rRNA sequences for species differentiation within Staphylococcus and Macrococcus, with sequence identity scores of 74-98% versus higher 16S rRNA percentages.
- Phylogenetic analysis of hsp60 sequences clearly separated the genus Macrococcus from Staphylococcus and showed Macrococcus clustering near the cytochrome c oxidase-positive sciuri group.
- The hsp60 gene phylogenetic tree correlated remarkably well with established taxonomy, revealing five major Staphylococcus subdivisions: aureus, epidermidis, haemolyticus, saprophyticus, and intermedius groups.
- Staphylococcus vitulinus and S. pulvereri showed 98% hsp60 and 99% 16S rRNA identity, supporting previous suggestions they may be the same species or subspecies.
- The hsp60 gene represents a reliable alternative to DNA-DNA hybridization and 16S rRNA sequencing for taxonomic classification and phylogenetic studies of Staphylococcus and Macrococcus species.
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Abstract
A 600 bp partial hsp60 gene sequence has been described previously as a novel genetic marker for species identification and phylogenetic studies within the genus Staphylococcus. In the present study, the 600 bp partial hsp60 gene sequences of 40 validly described Staphylococcus species and subspecies and four Macrococcus species were PCR-amplified and sequenced. Phylogenetic analysis revealed excellent concordance between the unrooted dendrograms based on partial hsp60 and 16S rRNA gene sequences. The genus Macrococcus is clearly separated from the genus Staphylococcus, but is closely related to the sciuri group, the only staphylococci that are cytochrome c oxidase-positive. The remaining Staphylococcus species clustered into five broad-based subdivisions, which corresponded to the aureus group, the epidermidis group, the haemolyticus group, the saprophyticus group and the intermedius group. These results agreed remarkably well with the current taxonomy of this diverse family, which is based on classical phenotypic and biochemical testing. Furthermore, pairwise sequence comparisons indicated that the hsp60 gene is more divergent and more discriminatory than the 16S rRNA gene for species differentiation among strains of the genera Staphylococcus and Macrococcus. It is concluded that the hsp60 gene may be an efficient alternative target for taxonomic and phylogenetic studies on members of these genera.