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1H c (2) - Pharmaceuticals (TH6/1) Effects of antibiotic pharmaceuticals on soil microorganisms: evaluation using selected soil biological test methods. Thiele-Bruhn, Sören1, Beck, Iris1, 2, Leinweber, Peter1, 1 University of Rostock, Rostock, MV, Germany2 GKSS Research Centre, Geesthacht, SH, Germany ABSTRACT- Residues of antibiotic pharmaceuticals are found in soils. Since antibiotics are designed to affect microorganisms at small concentrations, it is assumed that environmental residues influence soil microbial communities. However, published results from established soil microbial tests are contradictory. Thus, our objective was (A) to select suitable test methods and (B) to determine the effects on the activity and community structure of soil microorganisms depending on dose and incubation time and (C) to evaluate influencing parameters of the soils and antibiotics. For this purpose, selected tetracyclines and sulfonamides were investigated with different topsoil samples. While tetracyclines were rapidly and strongly fixed in soils, the sorption of sulfonamides varied with soil properties. Non-observable effects on various activity parameters were related to the fixation and the resulting low bioavailability of antibiotics. Effects were clearly time dependent, showing that test methods using short incubation times were not suitable. Additionally, bacteriostatic antibiotics required activation of microorganisms through nutrient addition. When the incubation time for substrate-induced respiration was extended into the growth phase of the microorganisms, clear dose-response relations were determined, depending on the type of antibiotic and its adsorption. In parts, significant effects were found for doses below the trigger value of 100 Key words: soil microorganisms, antibiotics, activity, community structure |
g kg-1. Due to the fixation of the antibiotics, effective concentrations were even lower. The investigated antibiotics affected especially soil bacteria, resulting in dose related and lasting shifts in microbial community structures, as determined from marker substances.