16S rRNA

An essential gene sequence that can be PCR amplified from all bacteria. Mutations have accumulated very slowly in variable (less conserved) regions. Provides a useful taxonomic (phylogenetic) marker because sequence variation will generally vary amongst species, with no affect on fitness. A highly sensitive diagnostic marker to detect Operational Taxonomic Units (OTUs) in DNA extracted from environment samples. Can be quantitative: the number of sequence reads per OTU will indicate the abundance of different species in the environmental sample