SRA

The process of natural transformation allows for the stable uptake, integration and functional expression of extracellular DNA1. This mechanism of horizontal gene transfer has been widely linked to the acquisition of antibiotic resistance and virulence factors. However, despite its importance in the evolution of the microbial pangenomes2, the role of natural transformation in the environmental fate and persistence of antibiotic resistance genes (ARGs) has been widely overlooked. Here, we demonstrate the ability of bromoacetic acid (BAA) – a regulated drinking water disinfection byproduct (DBP) – to stimulate natural transformation rates in the model organism Acinetobacter baylyi ADP1. We demonstrate that transformation stimulation in response to BAA is concentration-dependent and is linked to the ability of this compound to generate DNA damage via oxidative stress. In presence of BAA, transcription of restriction endonucleases were downregulated, indicating that such components of the DNA damage response are associated to the increase of transformation, presumably, due to a prolonged cytoplasmic persistence of the foreign DNA within the recipient cell. Lastly, we show that an artificial DBP cocktail simulating the environmental concentrations of five water DBP classes, stimulates natural transformation by almost 2-fold. The results of this study suggest that environmental mutagens may play an important role in determining the fixation rates of extracellular ARGs in the environmental metagenome.