Table 1 E. coli strains and plasmids used in this study

E. coli REL606

E. coli str. B F⁻, tsx-467(Am), araA230, lon⁻, rpsL227(strR), hsdR⁻, [mal⁺](LamS)

Richard E. Lenski

E. coli BL21(DE3)

E. coli str. B F⁻ompT gal dcm lon hsdS_B(r_B⁻m_B⁻) λ(DE3 [lacI lacUV5-T7p07 ind1 sam7 nin5]) [malB⁺]_K-12(λ^S)

F. William Studier

 pHCE-IIB

Expression vector carrying the ampicillin resistance gene and a high-level constitutive expression promoter (HCE)

[31]

 pHCE-IIB-HpaB(R379)

pHCE-IIB carrying hpaB with arginine at the 379th position [equivalent to hpaB of E. coli BL21(DE3)]

This study

 pHCE-IIB-HpaB(C379)

pHCE-IIB carrying hpaB with cysteine at the 379th position (equivalent to hpaB of E. coli REL606)

This study

 pHCE-IIB-HpaB(G379)

pHCE-IIB carrying hpaB with glycine at the 379th position (R379G substitution)

This study

 pHCE-IIB-HpaB(S379)

pHCE-IIB carrying hpaB with serine at the 379th position (R379S substitution)

This study