Heavy metal (Cu(II)) stress alters lysogeny-lysis balance and drives phage-mediated transfer of co-resistance in the activated sludge process.

High Cu(II) concentrations (10.00-20.00 mg/L) strongly promote phage-mediated horizontal gene transfer of resistance genes in activated sludge.

• Why it matters: Understanding how heavy metals influence resistance gene spread is crucial for ecological risk assessment and managing resistance in wastewater treatment systems.
• What they did: Researchers used metagenomics, metaviromics, and metatranscriptomics to analyze phage activity and gene transfer at varying Cu(II) levels in an activated sludge reactor, focusing on resistance gene dissemination.
• The result: HGT events of resistance genes mainly occurred at high Cu(II) levels, with nearly 40% of viral clusters carrying multiple resistance types, highlighting the role of temperate phages in resistance spread under metal stress.