27F

27F is a forward primer widely used in PCR to amplify the bacterial 16S rRNA gene. It targets a conserved region near the 5' end of the gene and is frequently paired with a reverse primer such as 1492R to generate amplicons for taxonomic identification and microbial ecology studies.

In typical workflows, the 27F/1492R pair yields near full-length 16S rRNA sequences, about 1,400 base pairs long. Shorter fragments are also common for high-throughput sequencing platforms, where the amplified region is chosen to balance read length with taxonomic resolution. The primer is valued for broad coverage across bacteria and archaea, enabling broad surveys of microbial communities while allowing downstream identification by sequencing.

Sequence and variants: The conventional 27F sequence is AGAGTTTGATCMTGGCTCAG, with degeneracies included to accommodate sequence variation (M = A/C). Some published forms use broader degeneracy, such as AGRGTTYGATYMTGGCTCAG, to improve universality across diverse taxa.

History and usage: 27F originated in the early 1990s as part of universal primer sets for 16S rRNA gene amplification and has since become a standard tool in microbiology, environmental microbiology, and clinical microbiology for microbial identification and community profiling.

Limitations: While effective across many taxa, 27F can introduce primer bias; mismatches to certain groups can reduce amplification efficiency, potentially underrepresenting those taxa in results. Primer choice and the target region influence observed diversity, so researchers may select alternative primers or regions for specific applications.