All commonly used research strains of E. coli belong to group A and are derived mainly from Clifton's K-12 strain (λ⁺ F⁺; O16) and to a lesser degree from d'Herelle's Bacillus coli strain (B strain)(O7).
Todas as cepas de investigación de E. coli que se usan normalmente pertencen ao grupo A e derivan principalmente da cepa K-12 de Clifton (λ⁺ F⁺; O16) e en menor medida da cepa B (O7) de Bacillus coli de d'Herelle.