Antibiotic stress enhances viral lytic activity and soil nitrogen mineralization processes

Nitrogen mineralization, a critical ecosystem process driven by microbial activity, converts organic nitrogen into plant-available ammonium. Viruses exert top-down control over microbial communities and their functions, thereby influencing nitrogen mineralization. However, how anthropogenic stressors such as antibiotics alter viral-mediated nitrogen cycling remains poorly understood. Here, we examined how antibiotic-induced viral activity regulated nitrogen mineralization in soil microcosms treated with ampicillin, ciprofloxacin, tetracycline, or kanamycin. Antibiotic exposure enhanced viral lysis activity by inducing prophages into the lytic cycle, increasing viral production by 13%-71%, 17%-57%, and 18%-76% (excluding ampicillin), on days 3, 7, and 11, respectively. This elevated viral lysis promoted the release of cellular nitrogen compounds, such as peptidoglycan, amino acids, and extracellular DNA, into the soil, leading to the accumulation of dissolved organic nitrogen (DON) and subsequently enhancing the formation of dissolved inorganic nitrogen. When a prophage inhibitor was applied alongside antibiotics, the viral-bacteria ratio decreased by 26%-53% on day 3, 8%-43% on day 7, and 10%-28% on day 11, while corresponding DIN concentrations declined by 17%-28%, 16%-28% (excluding ciprofloxacin), and 34%-51% over the same periods. Partial least square path modeling revealed that viral lysis directly promoted DON levels, which strongly drove ammonium formation. Random forest analysis demonstrated that viral lysis and nitrogen-containing cellular components most strongly influenced ammonium generation under ampicillin exposure, with progressively weaker effects under kanamycin, ciprofloxacin, and tetracycline. This study demonstrated that antibiotics enhanced nitrogen mineralization through prophage-mediated viral lysis, revealing a key mechanism by which antibiotics alter soil biogeochemical cycling via virus-host interactions.