Abstract Background Zinc oxide (ZnO), including its nanoparticulate form (ZnONPs), is widely used in agriculture and accumulates in the environment, where it may impose sustained selective pressure on microbial communities. However, the impact of prolonged zinc exposure on horizontal gene transfer and conjugation dynamics in Enterococcus faecalis remains poorly understood. Results We exposed Enterococcus faecalis OG1RF:pCF10 (donor) and OG1SSp (recipient) to prolonged zinc exposure (20 serial pa