16S rRNA gene sequencing is commonly used for identification and quantitation of microorganisms in complex biological mixtures, such as the human gut microbiome. The 16S rRNA gene is an excellent target gene for sequencing DNA in a heterogenous sample, as it is a highly conserved part of the transcriptional machinery. Universal PCR primers are used to amplify the conserved regions of 16S. Thus, it is possible to amplify the gene in a wide range of different microorganisms from a single sample. As the 16S rRNA gene consists of both conserved and variable regions, sequencing of the variable regions can be used to differentiate between different bacterial species.