16S – Proven Method of Identification
DNA sequencing provides a consistent, unambiguous data set that is reproducible from lab to lab. Genotypic ID is unlike phenotypic ID, which can be affected by differential expression of genes resulting in variable characteristics. The DNA sequence is stable and unchanging and is a tool for identification as well as a unique descriptor for the microorganism. Utilizing DNA sequences for tracking and trending, in some instances, can demonstrate that a single species of bacteria can be further divided into several subgroups.
In 1987, a review article by Carl Woese on bacterial evolution was published. Based on sequencing the small subunit of the ribosomal operon, it was demonstrated that all bacteria could be classified with a universal sequencing method. This was shown to be possible since the 16S rDNA is universally distributed among bacteria and contains species-specific variable regions. Additionally, the 16S rRNA gene has a mutation rate which is very close to the rate at which species diverge into new ones, making it ideal for species level identification.
Beginning in 1994, the publication of all new bacterial species 
required a full 16S gene sequence (approximately 1500 base pairs (bp)). For identification purposes, however, sequencing the first 500 bp is sufficient.
What is the 16S gene?
In bacteria, the small subunit of the ribosome (the organelle that is the site of protein synthesis in all living cells) contains the 16S rRNA which is transcribed from a ribosomal operon in the bacterial genome. The rRNA folds into an intricate 3D structure and is incorporated into a protein-RNA complex that is critical for the ribosomal function. The 16S gene is a multi-copy gene in most bacteria. When Accugenix extracts, amplifies and sequences the 500 bp target region, the resulting data represent a heterogeneous DNA population. Because there are multiple copies, some nucleotides may differ at the same position, resulting in polymorphic base calls. These are the result of evolutionary changes and can aid in species and even subspecies determination.
