This QIIME 2 plugin normalizes sequences by 16S rRNA gene copy number (GCN) based on rrnDB database (version 5.7). The plugin matches the taxa of sequences with the rrnDB-5.7pantaxastats_NCBI.tsv file, starting from the lowest taxonomic rank. If a match is found, the mean of GCN for the taxon is assigned; if not, the plugin will try to match a higher rank until the highest rank is met. All the unassigned sequences are assumed to have one GCN.