USING BIOLOGICAL REMEDIATION SYSTEM TO ADDRESS ANTIBIOTIC CONTAMINATION IN WATER SOURCES

Constant exposure of antibiotics from various sources in the environmental and incapability of wastewater facilities to decontaminate these organic compounds adversely impacts human health and the overall ecosystem. In our lab, a remediation system has been developed using vetiver grass (Chrysopogon zizanioides L. Nash) and its root-associated bacteria to remediate tetracycline (TC) from wastewater. The goal of this project was to develop a biological remediation system, and to understand the detoxification mechanisms used by vetiver and rhizospheric bacteria to detoxify these compounds. Uptake and transformation of TC was determined in the hydroponic remediation system, by monitoring levels of TC and its metabolites present in contaminated water and plant tissue. The samples were analyzed using Liquid Chromatography and Mass Spectrometry (LC-MS/MS) to assess the concentration of TC present in water samples. Plant uptake analysis was performed using SPE and LC-MS/MS to determine the TC concentration. TC-tolerant bacteria were isolated from vetiver roots and contaminated water during the course of remediation. Bacterial colonies that were highly tolerant to TC (minimum inhibitory concentration > 600 ppm) were selected and streaked for isolation. Three bacterial isolates were finally selected based on their capability to use TC as sole carbon and nitrogen source in basic media for further analysis. GC-MS and LC-MS/MS analysis was conducted on these bacterial samples under TC stress to assess the TC metabolizing capability of these bacteria. Results showed that, both vetiver and TC-tolerant bacteria biotransformed TC into its isomers, epi and anhydro-TC within 7 days and disappearance of the isomers was detected within about 14 days. Epi-TC and anhydro-TC are isomers of TC that are commonly detected in untreated water sources and are more harmful (carcinogenic) than its parent compound. Moreover, pathway analysis in vetiver shows possible role of GST (Glutathione S-transferase) in detoxification of tetracycline from water sources.