Overall Genome Relatedness Indices: Interpretation and Defining New Taxonomic Ranks

DNA-DNA hybridization (DDH) has been used as the gold standard in prokaryote taxonomy, but it is labor-intensive and prone to experimental errors. The development of high-throughput DNA sequencing technologies has greatly reduced the cost of genome sequencing, resulting in increased availability of microbial genomes. Traditional taxonomic methods, such as DDH, are being challenged by the rapid development of genomic metrics. Overall genome relatedness indices (OGRIs) have been developed to replace DDH. The present chapter describes the OGRI that has been developed as well as their interpretation for defining new taxonomic ranks.