In addition to microbial identification by fatty acid methyl ester (FAME) analysis, the Sherlock Software can also be used to identify microbes based on 16S/28S rRNA gene sequencing. Sherlock DNA begins where the DNA sequencer leaves off: with a textual consensus sequence. The advantage of this approach is that Sherlock DNA can be used with any sequencer from any vendor.
16S identification is a static technique, giving a constant result regardless of growth conditions. Further, 16S is extremely reproducible, with only slight run-to-run variation. The 16S gene is sequenced because it is highly conserved at the species level. Thus, different strains of the same species will have identical or nearly identical results. While 16S is more reliable for some species-level identification, when one desires strain-level information as well, FAME could be a better choice. And for specific genera, one technique or the other may be found to yield better results.
For even more information about a sample, one can use the Sherlock Software to process both FAME and 16S identifications and correlate the results in a single "polyphasic" report. Given that FAME and 16S are orthogonal techniques (techniques that rely on independent information from the samples), when the two techniques agree, the overall confidence in the result is greatly improved.
The Sherlock DNA Analysis mode allows for samples to be compared directly to one another, and results can be diplayed in a number of forms. These forms include the familiar Neighbor Joining trees and Sequence Alignment tools. Further, MIDI has developed a new display type, the Accurate Root Neighbor Joining tree, which is specially designed for comparing an unknown sample to a group of known samples.
Key Features of Sherlock DNA include:
- Validated libraries for bacterial ID (500bp and full gene 16S).
- Validated libraries for fungi/yeast ID (500bp 28S).
- Full integration with MIDI's Sherlock Software.
- Combined reporting of DNA-FAME results.
- DNA analysis tools for direct comparison of DNA samples.
- Custom DNA library development tools.
- Any DNA sequencer vendor can be used.