Journal
WATER RESEARCH
Volume 217, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2022.118434
Keywords
Antibiotic resistance gene; Wastewater treatment plants; Ammonia oxidation bacteria; Ammonia removal
Funding
- National Natural Science Foun-dation of China [51678565]
- Tianjin Natural Science Foundation [19JCYBJC23800]
- Special Fund of China [18J004]
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This study investigated the impact of a conjugative transfer plasmid RP4 on ammonia oxidation and found that the transfer of RP4 plasmid significantly inhibited the ammonia removal efficiency and suppressed the expression of functional genes related to ammonia oxidation in ammonia-oxidizing bacteria.
Antibiotic resistance genes (ARGs) have become an important public health concern. Particularly, although several ARGs have been identified in wastewater treatment plants (WWTPs), very few studies have characterized their impacts on reactor performance. Therefore, our study sought to investigate the effect of a representative conjugative transfer plasmid (RP4) encoding multidrug resistance genes on ammonia oxidation. To achieve this, we established sequencing batch reactors (SBRs) and a conjugation model with E. coli donor strains carrying the RP4 plasmid and a typical ammonia-oxidating (AOB) bacterial strain (Nitrosomonas europaea ATCC 25978) as a recipient to investigate the effect of conjugative transfer of plasmid RP4 on AOB. Our findings demonstrated that the RP4 plasmid carried by the donor strains could be transferred to AOB in the SBR and to Nitrosomonas europaea ATCC 25978. In SBR treated with donor strains carrying the RP4 plasmid, ammonia removal efficiency continuously decreased to 71%. Once the RP4 plasmid entered N. europaea ATCC 25978 in the conjugation model, ammonia removal was significantly inhibited and nitrite generation was decreased. Furthermore, the expression of several functional genes related to ammonia oxidation in AOB was suppressed following the transfer of the RP4 plasmid, including amoA, amoC, hao, nirK, and norB. In contrast, the cytL gene encoding cytochrome P460 was upregulated. These results demonstrated the ecological risk of ARGs in WWTPs, and therefore measures must be taken to avoid their transfer.
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