Virus decay and community composition in virus-amended sterile soil under slurry and unsaturated conditions

Soil viruses are abundant and diverse. The available research suggests viruses play a significant role in shaping the structure and function of soil microbial communities. Their effects are modulated by various environmental factors, including soil temperature, moisture, and geochemical conditions. This study investigated the persistence/inactivation of naturally occurring soil viruses added to sterilized soil, providing insights into virus decay under abiotic conditions. Soil microcosm experiments under saturated (slurry) conditions (5 g:12 mL) and unsaturated conditions (60% of field capacity) revealed a consistent decline in viral abundance over time. Under saturated conditions, there was a reduction of over 90% in viral abundance after 10 d, a steeper decline than the 55% reduction observed under unsaturated conditions during the same length of incubation. Notably, the composition of viruses also changed over time, and the remaining viruses demonstrated infectious capabilities for up to 13 d in saturated and 16 d in unsaturated soil, evidenced by changes in viral abundance upon the addition of live bacteria. Introducing live bacteria reduced the net viral dissipation in saturated soil but resulted in a net increase in viral abundance in unsaturated soil from 4.49 × 108 to 6.76 × 109 within 3 days. The increase in viral abundance in the unsaturated soil was partly due to the emergence of new viruses from prophage induction. This research presents a preliminary exploration into extracellular persistence of soil viruses under varying moisture conditions.