Fate of antibiotic resistant bacteria in two different constructed wetland types

CAMILA KNECHT; M. KRÜGER; A. BUCHHOLZ; H. DAMBECK; J. NICKOLAUS; A. AHMED; S. KELLMANN; I. MÄUSEZAHL; M. MÖDER; M. KÄSTNER; H. KÖSER; O. O. ADELOWO; J. NIVALA; J. A. MÜLLER

Leipzig

Simposio; 17th International Symposium on Microbial Ecology; 2018

Horizontal Gene Transfer (HGT) of Antibiotic Resistance Genes (ARG) in aquatic environments drives the development of novel Antibiotic Resistant Bacteria (ARB).This transfer can be substantial in wastewater treatment plants, where diverse microorganisms and various types of environmental stress are found. Constructed Wetlands (CWs), near-natural wastewater treatment options, can serve as model systems to illuminate more clearly the driving forces for HGT of ARG in aquatic ecosystems. Towards the aim of identifying such forces, we enumerated selected ARB, ARG, and class 1 integrons by culture-independent and culture-dependent methods in two horizontal-flow CWs receiving pre-treated municipal wastewater.One CW was aerated and the other was not. In addition, bacterial community profiling was carried out via 16S amplicon sequencing, and water samples were also analyzed for conventional wastewater parameters and antibiotics. Results showed a significant attenuation of resistance indicators in the effluent of both wetlands.However, in the aerated CW the relative abundance of some ARG and class 1 integrons increased along the flow path, which is an indicator for HGT. In the same CW, the abundance of cultivable Escherichia coli declined more steeply than their numbers based on molecular methods, which suggests that oxidative stress was acting on cells. There are two main conclusions: (1) CWs are a suitable technology to remove ARB/ARG from wastewater, with aerated systems performing better in terms of absolute abundance attenuation; (2) aeration could constitute an important stress factor, triggering an increase in HGT of some ARG, depending on their genetic context.