Using the 16S-23S rRNA operon sequence instead of the 16S rRNA sequence offers several advantages. Firstly, the 16S rRNA sequence, although widely used for microbial identification and taxonomy, has limitations in resolving closely related species. The 16S-23S rRNA operon, being a longer sequence, includes more genetic information, thus allowing for higher species resolution. Secondly, the internal transcribed spacer (ITS) regions between the 16S and 23S rRNA genes show higher variability at the species level, providing additional discriminatory power. These ITS regions are particularly useful for distinguishing closely related species. Lastly, the 16S-23S rRNA operon includes the entire set of ribosomal RNA genes, which are crucial for protein synthesis. Analyzing the full operon provides a more comprehensive view of microbial function and evolutionary relationships, enhancing our understanding of microbial diversity and evolution.
In the MIrROR v.1.0 database, the operon sequences were trimmed to exclude the primer regions defined by 16S-27F (5'-AGRRTTYGATYHTGGCCTCAG-3') and 23S-2241R (5'-ACCRCCCACGAGTTHRAACT-3'). However, the MIrROR v.2.0 database provides the entire 16S-23S operon sequence, including these primer sites. By providing the complete sequence, researchers can utilize the data for a variety of research purposes without being restricted to specific primer-defined regions and allows for more detailed and flexible experimental designs.
Additionally, the "Primer Match Finder" tool is available to help researchers determine if their primers are applicable to the sequences in the MIrROR database. This tool provides outputs such as the binding sites of the primers within the operon, the exact sequences that match the primers, and target species information. These outputs allow researchers to assess the suitability and effectiveness of their primers for their specific research needs, ensuring that they can design and validate their experiments with greater accuracy and confidence.
In MIrROR version 1.0, duplicate sequences from the same species were removed to streamline the database and reduce redundancy. However, MIrROR version 2.0 retains these duplicates. By maintaining sequences that were previously randomly deleted as "intraspecies identical sequences," MIrROR v.2.0 ensures it does not reduce the number of genomes it covers. While this approach increases the database size and resource demands, it allows researchers to select and analyze specific sequences that are most suitable for their studies.
Additionally, to ensure accurate taxonomic profiling, all redundant or similar sequences between different species have been removed, maintaining the integrity of cross-species comparisons. This comprehensive approach, which excludes interspecies redundancies while inclusively covering intraspecies duplicates, balances data richness and analytical precision, providing a robust resource for various research applications.