Cu(II) and Zn(II) Enhance Antibiotic Resistance Gene Transformation by Regulating Type IV Pili-Mediated DNA Uptake

< 0.05). T4P sensitively responded to the two metals at concentrations as low as 0.5 μM within 2 h, preceding any detectable oxidative stress responses. At the initial phase of T4P-mediated uptake (DNA binding), Cu(II) enhanced extracellular ARGs adhesion by inducing DNA condensation and strengthening T4P-DNA binding via ionic bridging. During the latter phase (DNA pulling), Zn(II) functioned as a cofactor for T4P ATPase, stimulating pilus extension-retraction dynamics to facilitate DNA transformation. At higher concentrations (8 μM), the CpiR-CpiA regulatory axis serves as a molecular brake, curtailing T4P dynamics by derepressing the PilB-inhibitor CpiA and thereby attenuating transformation enhancement. These findings reveal that Cu and Zn interfere with different phases of T4P-mediated DNA uptake, highlighting a previously unrecognized mechanism by which metals accelerate ARG dissemination in the environment.