Horizontal transfer of antibiotic resistance genes in a membrane bioreactor.
Growing attention has been paid to the dissemination of antibiotic resistance genes (ARGs) in wastewater microbial communities. The application of membrane bioreactors (MBRs) in wastewater treatment is becoming increasingly widespread. We hypothesized that the transfer of ARGs among bacteria could occur in MBRs, which combine a high density of bacterial cells, biofilms, and antibiotic resistance bacteria or ARGs. In this study, the transfer discipline and dissemination of the RP4 plasmid in MBRs were investigated by the counting plate method, the MIDI microorganism identification system, and quantitative polymerase chain reaction (qPCR) techniques. The results showed that the average transfer frequency of the RP4 plasmid from the donor strain to cultivable bacteria in activated sludge was 2.76×10⁻⁵ per recipient, which was greater than the transfer frequency in wastewater and bacterial sludge reported previously. In addition, many bacterial species in the activated sludge had received RP4 by horizontal transfer, while the genera of Shewanella spp., Photobacterium spp., Pseudomonas spp., Proteus spp., and Vibrio spp. were more likely to acquire this plasmid. Interestingly, the abundance of the RP4 plasmid in total DNA remained at high levels and relatively stable at 10⁴ copies/mg of biosolids, suggesting that ARGs were transferred from donor strains to activated sludge bacteria in our study. Thus, the presence of ARGs in sewage sludge poses a potential health threat.
Department of Environment and Health, Institute of Health and Environmental Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, No. 1, Dali Road, Tianjin 300050, China.
Dong
D
Yang
Jingfeng
J
Wang
Zhigang
Z
Qiu
Min
M
Jin
Zhiqiang
Z
Shen
Zhaoli
Z
Chen
Xinwei
X
Wang
Bin
B
Zhang
Jun-Wen
JW
Li
D001419:Bacteria / Q000235:genetics*; D018441:Biofilms / Q000254:growth & development; D019149:Bioreactors; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D010776:Photobacterium / Q000235:genetics; D011511:Proteus / Q000235:genetics; D011549:Pseudomonas / Q000235:genetics; D011815:R Factors / Q000235:genetics*; D012722:Sewage / Q000382:microbiology; D020592:Shewanella / Q000235:genetics; D014733:Vibrio / Q000235:genetics
D012722:Sewage
Antibiotic resistance genes; Dissemination and persistence; Horizontal transfer; Membrane bioreactor