Next-generation sequencing of 16S ribosomal RNA is widely used to survey microbial communities. Sequences are typically assigned to Operational Taxonomic Units (OTUs). Closed- and open-reference OTU assignment matches reads to a reference database at 97% identity (closed). then clusters unmatched reads using a de novo method (open). https://www.marcelovicente.com/product-category/vita-c-conditioner/