BotanyGTP
16S rDNA Bacterial Tag-encoded FLX Amplicon Pyrosequencing reveals Microbial Diversity within a Groundwater Treatment Plant at a 1,2-Dichloroethane Impacted Site
The Botany Sands aquifer in south Sydney is contaminated with 1,2-dichloroethane (DCA). To contain and remediate this contamination, a groundwater treatment plant (GTP) was constructed by Orica, the main occupant of the Botany Industrial Park. The GTP uses air stripping and incineration to remove DCA, but this is expensive and energy-intensive.  As an alternative, the feasibility of bioremediation for DCA removal was investigated using a membrane bioreactor (MBR).     The objectives of this study were to monitor changes in the bacterial community of the MBR as it adapted from treating air-stripped groundwater to raw groundwater, and to correlate specific bacterial groups to DCA biodegradation in the MBR. The method used was tag-linked pyrosequencing of amplified 16S rRNA genes.      The Botany MBR was colonised predominantly by alpha- and beta-Proteobacteria. Initially, Rhodobacter dominated, but as the raw groundwater content increased, the community diversified to include Methylibium, Azoarcus, Thiobacillus, Thiothrix and Leptothrix. Genera that include known DCA-degraders (Ancylobacter, Xanthobacter) peaked in abundance mid-way through the time course at 13% and 3% of total sequences, respectively, but then declined, despite continued efficient removal of DCA by the MBR. Correlation of 16S sequence abundances with qPCR counts of dehalogenase genes (dhlA) at different time-points suggested that Azoarcus spp were involved in DCA biodegradation at the later stages.     This study illustrates the usefulness of 16S-pyrosequencing for revealing community dynamics in industrially-significant microbial ecosystems, and especially the power of combining pyrosequencing data with catabolic gene qPCR for identifying bacterial groups involved with specific biodegradation processes.