Uptake and Transformation of Tetracycline by Vetiver Grass (Chrysopogon zizanioides L. Nash).

Overuse and improper handling and disposal of antibiotics have raised some serious concerns worldwide.  Wastewater treatment facilities are usually not equipped to remove antibiotics and hence release these compounds into the environment, allowing for them to potentially impact human health.  This study focuses on determining the potential of using Vetiver grass to remediate tetracycline (TC), one of the broad-spectrum antibiotics widely used in humans and animals. Uptake and transformation of TC was determined in an aquatic remediation system, by monitoring TC and its metabolites present in contaminated water and plant tissue. Hydroponic tanks containing different concentrations of TC (25, 50, 75, 150 and 250 ppm) were used to grow Vetiver plants for 30 days. Levels of TC and its derivatives were determined in the contaminated water and in plant tissues.  A method was developed optimizing the conditions suitable for eluting TC and its isomers anhydrotetracycline (ATC) and epitetracycline (ETC) on a C18 column using isocratic and gradient elution in HPLC and LC-MS/MS.  The results suggest that there is significant transformation of TC in tanks with plants compared to the tanks without plants. Uptake of TC by Vetiver was higher from tanks with lower concentrations of TC compared to the higher concentrations.  Transformation of TC mainly occurred during the first 5 days.  The HPLC data indicate that, there was a decrease in the parent compound and an increase in the concentration of the isomers (ATC and ETC) between 5 and 15 days. Concentrations of ATC and ETC then decreased and eventually disappeared from the tanks between 20 and 30 days.  Work is in progress to decipher the specific roles of plant (by analyzing the roots and shoots separately for translocated TC degradates) and root-associated bacteria in the transformation/degradation of TC in this aquatic system.