Tuesday, November 14, 2006 - 2:05 PM

Manure-Borne Tetracyclines: Fate in Soil and Evidence of Plant Uptake.

Diana S. Aga, James Berry, Seamus O'Connor, and Michael Farkas. Univ of New York-Buffalo, Dept of Chemistry, 611 Natural Science Complex, Buffalo, NY 14260

The persistence of manure-borne tetracycline in soil was investigated under field conditions for over a period of two years.  Soil samples were analyzed by enzyme-linked immunosorbent assay (ELISA) and/or by liquid chromatography-mass spectrometry (LC-MS). Whereas LC-MS showed that tetracycline declined to <50% of its initial soil concentration after 3 weeks, ELISA showed that the total tetracyclines did not decline significantly 5 months after manure application.  The differences between ELISA and LC-MS results are attributed to the broad cross-reactivity of the antibodies employed, which detect many structurally related tetracyclines, including their isomers and degradation products.  In addition, results of greenhouse experiments indicating that the presence of tetracyclines in soil could affect growth of some crop plants will be presented.  For instance, when grown in chlortetracycline-treated soil, the leaves and pods of pinto beans were significantly smaller than the control plants (no chlortetracycline treatment).  On the other hand, no significant differences in growth were observed between maize grown in chlortetracycline-treated soil versus the untreated soil.  Biochemical assays indicate that maize has the ability to detoxify chlortetracycline via the glutathione conjugation pathway, as revealed by a 2-3 fold increase in the glutathione transferases (GST) activity in the treated maize relative to untreated plants.  Mass spectral analysis of both the GST enzymes and the glutathione-chlortetracycline conjugates from maize provides further evidence of induced production of the GST stress proteins after plant uptake of antibiotics from soil.