An active p_axe promoter is required for axe-txe mediated stable plasmid maintenance.

Stability assays were conducted with derivatives of the stability probe vector, pFH450: pREGΔaxe-txe does not contain any accessory stability determinants (circles), pREG531 contains the axe-txe cassette (squares), and pREGpaxemut contains the axe-txe cassette with a mutated p_axe promoter (triangles). Assays were performed as outlined in Materials and Methods. Results are averages of at least five experiments for which the standard deviation did not exceed 15%.