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.bekindtopets.com/special-pick-Best-Shot-UltraMAX-Pro-Clarifying-Shampoo-save-big/