A Carotenoid- and Nuclease-Producing Bacterium Can Mitigate Enterococcus faecalis Transformation by Antibiotic Resistance Genes.

Dissemination of antibiotic resistance genes (ARGs) through natural transformation is facilitated by factors that stabilize extracellular DNA (eDNA) and that induce reactive oxygen species (ROS) that permeabilize receptor cells and upregulate transformation competence genes. In this study, we demonstrate that can mitigate this ARG dissemination pathway by removing both eDNA and ROS that make recipient cells more vulnerable to transformation. We used plasmid RP4 as source of extracellular ARGs (, , and ) and the opportunistic pathogen as receptor. The presence of significantly reduced the transformation frequency from 2.5 ± 0.7 × 10 to 7.4 ± 1.4 × 10 ( < 0.05). Based on quantification of intracellular ROS accumulation and superoxide dismutase (SOD) activity, and quantitative polymerase chain reaction (qPCR) and transcriptomic analyses, we propose two mechanisms by which mitigates transformation by ARGs: (a) residual antibiotics induce to synthesize liposoluble carotenoids that scavenge ROS and thus mitigate the susceptibility of for eDNA uptake, and (b) eDNA induces to synthesize extracellular nucleases that degrade eARGs. This mechanistic insight informs biological strategies (including bioaugmentation) to curtail the spread of ARGs through transformation.