Fig. 2

Example division of the Campylobacter coli pangenome into unique, accessory, and core genomes. a Distribution of gene frequencies P(x), or the number of times a gene is observed in a genome, with peaks at very low (“unique”) and very high (“core”) frequencies. The corresponding cumulative distribution F(x) is shown below. b Log-log plots of the frequency distribution at very low and very high frequencies showing approximately linear trends, and the corresponding models of P(x) as the sum of two power functions and F(x) as the integral. N is the total number of genomes. c Division of the pangenome into unique, accessory, and core genomes based on the cumulative distribution fit. Frequency thresholds for unique and core genes are defined relative to the fitted inflection point