![]() ![]() The 16S rRNA is suitable for this purpose for several reasons. The gene is universally distributed, allowing the analysis of phylogenetic relationships among distant taxa. As a functionally indispensable part of the core gene set, the 16S rRNA gene is expected to be only weakly affected by horizontal gene transfer, which further supports its use for phylogenetic studies. Despite the above, 16S rRNA is still subject to variation, especially in certain variable regions. While the presence of variable regions allows sufficient diversification to provide a tool for classification, the presence of conserved regions enabled the design of suitable PCR primers or hybridization probes for various taxa at different taxonomic levels ranging from individual strains to whole phyla. ĭespite the wide use of 16S rRNA, there are several aspects that limit the interpretation of 16S rRNA-derived results. The most important is the fact that its copy numbers per genome vary from 1 up to 15 or more copies. Copy numbers seem to be taxon-specific to some extent, but variation among strains of the same species has also been recorded. ![]() The numbers of rRNA copies have been put into context with the life strategy of bacteria because the rRNA copy number of some taxa are correlated with their ability to respond to favorable growth conditions. Taxa with low copy numbers have been assumed to be more oligotrophic. ![]()
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