Project Details
Projekt
Effects of irrigation water quality and soil type on the soil and plant associated microbiome, abundance, diversity and transferability of antibiotic resistance genes in Gram-positive bacteria
Applicant
Professorin Dr. Elisabeth Grohmann
Subject Area
Soil Sciences
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 431531292
Wastewater irrigation is a common practice in many areas of the world. Irrigation with untreated wastewater in the past resulted in an accumulation of chemical pollutants like pharmaceutical residues and disinfectants in soils. Changes of the irrigation regime to irrigation with treated wastewater are under way in many countries, as it is the case in the Mezquital Valley. However, there is only scarce information on the microbial, chemical pollutant and antimicrobial resistance gene dynamics in terms of the change of the irrigation scheme. We hypothesize that benefits from the installation of wastewater treatment in long-established wastewater irrigation systems can at least transiently be compromised because i) change from irrigation with untreated wastewater to irrigation with treated wastewater releases pollutants that have accumulated in soil in the past, ii) environmental concentrations of pollutants in treated or untreated wastewater and those released from soil and taken up by plants are high enough to select antibiotic resistance and trigger horizontal gene transfer in soils and plants, with iii) the soil type modulating the release of pollutants and the associated selection of antibiotic resistance. SP 4 will test these hypotheses with the three soil types Leptosol, Phaeozem and Vertisol for highly used antimicrobial agents differing in structure and mode of action (sulfamethoxazole, trimethoprim, ciprofloxacin, clindamycin, erythromycin, azithromycin) and quaternary alkylammonium compound disinfectants (alkyltrimtethylammonium, dialkyldimethylammonium and benzylalkylammonium compound) in the three joint experiments of the Research Unit. We will investigate the impact of varying pollutant concentrations on the composition of the microbial community (bacteria, archaea, fungi) and the abundance of pathogenic Gram-positive bacteria in wastewater, treated wastewater, soil and plant samples by culture-independent methods (in collaboration with SP 5). We will determine the concentrations of antibiotic resistance genes and conjugative plasmids by quantitative real-time PCR in wastewater, treated wastewater, soil and plant samples (in collaboration with SP 5), we will sequence conjugative resistance plasmids from Gram-positive pathogens (provided by SP 6), and allocate selected plasmids to SP 3 for fitness and minimal selective concentrations tests. Moreover, we will determine horizontal resistance transfer rates among Gram-positive bacteria in selected wastewater, soil and plant samples (in collaboration with SP 5) by a plasmid capturing method developed by SP 4. In this way, SP 4 delivers microbial and resistance dynamics data for the conceptual and quantitative model to be developed by SP 7 and contributes to an integrated view on the effect of wastewater treatment on the interaction between pollutants and bacteria carrying antibiotic resistance genes in wastewater irrigation systems.
DFG Programme
Research Units
