Hypoxia triggers the proliferation of antibiotic resistance genes in a marine aquaculture system

The transmission of antibiotic resistance genes (ARGs) affects the safety of aquaculture animals. Dissolved oxygen (DO) can affect the transmission of ARGs, but its mechanism of action in this process is unclear. We conducted labora-tory breeding experiment with low and control DO groups. Combined quantitative PCR and 16S rRNA sequencing to study the effect of DO on the spread of ARGs. Hypoxia treatment significantly increased the accumulation of ammo-nium and nitrite in aquaculture water, and it increased the relative abundances of ARGs and mobile genetic elements (MGEs), especially the ARGs resistant to drugs in the categories of sulfonamide, (flor)/(chlor)/(am)phenicol, and MLSB (macrolide, lincosamide and streptogramin B) and the MGE intI-1(clinic), by 2.39-95.69 % in 28 days relative to the control DO treatment. Though the abundance of ARG carries, especially the Rhodocyclaceae, Caldilineaceae, Cyclobacteriaceae, Saprospiraceae, Enterobacteriaceae, Sphingomonadaceae families, showed higher abundance in low DO groups, relating to the vertical transmission of ARGs. Hypoxia treatment is more likely to promote the horizon -tal gene transfer (HGT)-related pathways, including ABC transporters, two component system, and quorum sensing, thus to induce the HGT of ARGs. The changed bacterial proliferation also altered the abundance of MGEs, especially intI-1(clinic), which induced HGT of ARGs as well. Additionally, pearson correlation results revealed that the succes-sion of bacterial community function played the strongest role in ARG proliferation, followed by bacterial community structure and MGEs. Our results highlight the importance of suitable DO concentration in controlling the spread of ARGs especially the HGT of ARGs. In the context of global attention to food safety, our results provide important infor-mation for ensuring the safety of aquatic products and the sustainable development of aquaculture.

Automated summary

The concentration of dissolved oxygen affects the spread of antibiotic resistance genes (ARGs). Low oxygen treatment increases the accumulation of ammonium and nitrite and the abundance of ARGs and mobile genetic elements (MGEs), especially ARGs resistant to drugs such as sulfonamide, chloramphenicol, and macrolides. This study highlights the importance of oxygen concentration in controlling the spread of ARGs, especially through horizontal gene transfer.