Molecular Analysis of Bacterial Community Dynamics During Bioaugmentation Studies in a Soil Column and at a Field Test Site

摘要

1,1,1-Trichlorethane (1,1,1-TCA), a widely used industrial solvents, is one of the most common subsurface contaminants. Transformation processes in the subsurface can result in the production of 1,1- dichloroethane (1,1-DCA) and 1,1-dichloroethene (1,1-DCE) from 1,1,1-TCA contamination, resulting in plumes of mixed chlorinated aliphatic hydrocarbons (CAHs). A butane-utilizing microorganism, strain 183BP, with the ability to cometabolically transform 1,1, 1-TCA, 1,1-DCA, and 1,1-DCE was isolated from environmental samples taken from a CAH contaminated site. Two bioaugmentation treatment tests with strain 183BP as inoculum were conducted at the Moffett Federal Airfield In-Situ Bioremediation Test Site (Moffett Field), Mountain View, California. Also, a soil column packed with aquifer solids and groundwater obtained from Moffett Field was inoculated with strain 183BP and operated under conditions similar to those used in the field tests. Field groundwater samples and soil column effluent samples were analyzed using techniques based on 16S rRNA gene analysis. 183BP-specific primers were designed and used in real-time SYBR Green I PCR analyses to detect and quantify the inoculated microorganisms in the subsurface. Dynamics of the bacterial community composition were investigated using terminal restriction fragment length polymorphism (T-RFLP) methods and statistical analysis. During the first bioaugmentation test in the absence of 1,1-DCE, maximum treatment efficiencies for TCA and DCA were approximately 80% and 96%, respectively in the bioaugmented well leg, while essentially no transformation occurred in the non- bioaugmented control leg. During the effective treatment period, the 183BP cell concentration was above 900 cells/ml in groundwater obtained 0.5 m from the injection well. In the second bioaugmentation test, 1,1-DCE was added to the influent CAH mixture and was effectively transformed in the bioaugmented well leg.