Calcium peroxide orchestrates virus-induced heavy metal resistome via shaping humeomics in sludge composting

This study aims to investigate the impact of calcium peroxide (CaO2) on compost humeomics and its effect on the toxicity removal of heavy metals (HMs), viral communities, and heavy metal resistance genes (HMRGs) during composting. The results indicate that CaO2 reduced the concentrations of toxic HMs As and Ni by 2.08 mg/kg and 10.41 mg/kg, respectively, compared to the control group (CK). Furthermore, it led to an increase in the stable fractions of As, Cu, Fe, and Ni by 6.32 %, 13.23 %, 3.09 %, and 3.01 % in the treatment group (T), respectively. CaO2 facilitated the transformation of heavy metal components, mitigated their harmful effects, induced their stabilization, and enhanced the humic quality. Metagenomic analysis shows that CaO2 effectively reduces the abundance of viruses (VRs) associated with HMRGs, leading to the inhibition and removal of HMRGs. Network analysis reveals that VRs, such as g__unclassified_f__Pithoviridae and g__unclassified_d__Viruses, which are related to toxic HMs, play a key role in regulating the hazardousness of pollutants in compost, and their abundance is effectively reduced by CaO2. Finally, mantel test analysis confirms that the Fenton-like reactions triggered by CaO2 and the succession of viral communities are crucial factors in pollutant removal. These results collectively indicate that under the influence of CaO2, the hazardousness of HMs, VRs, and HMRGs in the composting process is reduced, and they are effectively inhibited and removed.