v1v2v3

v1v2v3 refers to the V1, V2, and V3 hypervariable regions of the bacterial 16S ribosomal RNA gene, commonly targeted together in amplicon sequencing to profile microbial communities. The 16S rRNA gene contains nine hypervariable regions (V1–V9) interspersed with conserved sequences, and different regions offer varying taxonomic resolution and primer bias. The V1-V3 segment spans roughly the first half of the gene, with amplicons typically about 500–550 base pairs in length, making it compatible with older sequencing platforms and with paired-end reads on modern platforms.

In standard workflows, primers flank the V1-V3 region, followed by PCR amplification, sequencing, and downstream processing. Reads are merged, quality-filtered, and clustered into operational taxonomic units (OTUs) or resolved into amplicon sequence variants (ASVs). Taxonomic assignment is performed by comparing sequences to reference databases such as SILVA, Greengenes, or RDP. The choice of region affects observed community composition; V1-V3 can offer higher resolution for certain taxa, but primer bias and differential amplification can skew abundance estimates, and cross-study comparability is limited when different regions or primer sets are used.

Applications include profiling bacterial communities in environmental samples, clinical specimens, and host-associated microbiomes. The v1v2v3 approach remains one option among others (such as V4, V3-V4) depending on the research question, available sequencing technology, and desired taxonomic resolution.