Tetracycline behaviour in two prairie waters and the effects of tetracycline on microbial processes

B. Verma, R. D. Robarts, J. V. Headley and K. M. Peru

Abstract

Photolysis kinetics of tetracycline was measured in non-sterile distilled, river and pond waters in both the laboratory and in natural sunlight with or without the presence of UV radiation. A volume of 100 ml of distilled, river and pond water, in duplicate, were placed in flasks and spiked with tetracycline (Sigma Canada) at concentrations of 500, 1000 and 4000 mg L-1. For the laboratory experiments, one treatment was performed in the dark while another was conducted in the light. The flasks were sub-sampled daily for the duration of the experiment, a period of 12 days. For the natural sunlight experiment, the flasks were placed in a water bath (21± 3°C) under natural light conditions and the waters were sampled every 15 minutes. In both the laboratory and natural sunlight experiments, tetracycline was determined using a Quattro Ultima LC/MS/MS. Additionally, experiments were performed to measure the effect of tetracycline, at two concentrations, 500 and 4000 mg L-1, on microbial biofilms growing on decaying Scirpus stems. Scirpus stems, in glass flowcells, were allowed to decay with or without the presence of tetracycline. Laser microscopy was used, in conjunction with fluorescent probes, to follow, in-situ, microbial colonization of the stems over 33 days. Scion Imaging software was used for image analysis. In general, the photolysis of tetracycline was observed to follow first order kinetics with enhanced degradation rates in the presence of UV radiation. For the microbial studies the higher concentrations of tetracycline significantly stunted the colonization of Scirpus stems.