known to enhance eDNA uptake and integration, including UV light, disinfection chemical byproducts and pharmaceuticals.
"Several studies have highlighted the potential impact of individual stressors in chlorinated wastewater on bacterial horizontal gene transfer," Al-Gashgari says. But in a real wastewater environment, multiple stressors co-exist."Our aim was to understand the effects of these factors in combination," she says.
The researchers hypothesized that multiple stressors would have an additive effect on the gene-transfer rate. Surprisingly, a far more complex picture emerged, Hong says. Depending on their modes of action, some combinations produced a synergistic large increase in gene-transfer rate, some had a neutral effect, while others decreased it.
This complexity makes the combinatorial effect of multiple stressors difficult to predict, complicating the ability to assess whether unintentional consequences can arise in the downstream reuse environment, says Hong. However, the findings show clear conclusions on wastewater treatment, she says. The key goal should be to keep the bacteria and eDNA in wastewater at such low concentrations that gene transfer is minimized.facilities should retrofit microfiltration membranes because they can remove both bacteria and extracellular DNA to levels that would not facilitate natural transformation," Hong says."Installing and operating membrane microfiltration would be more expensive than sand filtration, but we urge utilities to take this precautionary approach.