Average Nucleotide Identity (ANI)
Average Nucleotide Identity (ANI)
Average Nucleotide Identity (ANI) is a measure of genomic similarity at the nucleotide level between two different genomes. NCBI uses ANI to evaluate the taxonomic identity of genome assemblies, primarily for prokaryotes. The results of ANI analysis can also be used to identify contaminated sequences in genome assemblies.
The report file prokaryote_ANI_contamination.txt provides information about assemblies assigned as contaminated by ANI thresholds. For more information about this file, see the README.
For more information on ANI, see our ANI Overview.
ANI criteria for assigning a genome as contaminated
- At least 5% of the genome assembly or 200 kb flagged as contaminant, whichever is smaller
- Contamination derived from an organism in a different taxonomic family, with rule exceptions in cases of known paraphyly or expected close relationships