HR: 1340h
AN: H33D-1629    [Abstracts]
TI: Molecular Probes: A Tool for Studying Toxicity of VOCs to P.Putida F1
AU: * Singh, R
EM: rs443@drexel.edu
AF: Department of Civil Architectural and Environmental Engineering, Drexel University, 3141 Chestnut St., Philadelphia, PA 19104, United States
AU: Olson, M S
EM: mso28@drexel.edu
AF: Department of Civil Architectural and Environmental Engineering, Drexel University, 3141 Chestnut St., Philadelphia, PA 19104, United States
AB: Volatile Organic Compounds (VOCs) are of great concern in ground water remediation, and are generally present in the form of NAPLs in subsurface environments. Among the various treatment technologies, in situ bioremediation is one of the most effective and low-cost treatment options. Many soil bacteria are reported to degrade these organic contaminants via metabolism (using them as a source of carbon to derive energy) or co- metabolism up to certain concentrations. However, larger concentrations of these contaminants are toxic to bacteria. Thus, in order to achieve successful bioremediation, it is important to determine the optimal concentrations of various contaminants that is beneficial for the activity and survival of degrading bacteria. The purpose of this study is to develop a novel method for toxicity analyses of VOC contaminants to the soil bacteria that degrade them. The present study is based on a two-color fluorescence assay of bacterial viability which facilitates actual counting of live and dead bacteria. Pseudomonas putida F1 cells were labeled with a LIVE/DEAD^® BacLight^TM bacterial viability kit (Invitrogen), which consists of a mixture of two dyes, SYTO 9 and propidium iodide, each with a different ability to penetrate healthy bacterial cells. Live cells stain green whereas propidium iodide (red dye) only penetrates cells with compromised membranes that are considered dead or dying. Stained cells were exposed to different concentrations of trichloroethylene (TCE) and toluene in sealed vials. Change in the concentrations of green and red cells were monitored over the time using fluorescence microscopy. UTHSCSA ImageTool software was used to count the live and dead cells in the images. It was observed that live (green) cell concentrations decreased and dead/damaged (red) cell concentrations increased over time when cells were exposed to TCE. No significant changes were observed in control experiments. Death rate constants calculated based on live cell disappearance and dead/damaged cell appearance were found to be approximately equal for TCE. Results will be presented in terms of dose response and death rate curves. Death rate constants and minimum inhibitory concentrations for survival of P. Putida F1 exposed to TCE and toluene will be compared.
DE: 0418 Bioremediation
DE: 1832 Groundwater transport
DE: 1895 Instruments and techniques: monitoring
DE: 1899 General or miscellaneous
SC: Hydrology [H]
MN: 2007 Fall Meeting