TABLE 1.

Pangenome analysis of E. coli, 1997-2018. Core genes are all genes shared among all strains belonging to the species E. coli as defined by the 16S rDNA sequence.

Reference	Number of E. coli strains sequenced	Number of core genes	Number of pan-genome genes
Blattner et al. (1997)	1	--	4,288
Perna et al. (2001)	2	4,029	5,416
Rasko et al. (2008)	17	2,200	>13,000a
Sun et al. (2016)	26	2,168	6,797
Her et al. (2018)	59	2,874	15,950
Kaas et al. (2012)	186	1,702	16,373
Yang et al. (2018)	491	867	43,415

^a Extrapolated.