Abstract
Ralstonia eutropha KT-1 is a bacterium that can grow on phenol or toluene. Strain KT-1 is also able to degrade trichloroethylene (TCE) after the induction with phenol or toluene. Approximately 2 kg (dry weight) of strain KT-1 induced by toluene was injected into groundwater at a TCE-contaminated site to degrade TCE. After the injection process was completed, the groundwater was pumped up for 51 days. Number of phenol-degrading bacteria in the groundwater was monitored by most probable number (MPN) method during that period. Changes of bacterial populations in the groundwater were also analyzed by molecular methods based on 16S rDNA to evaluate impacts of strain KT-1 injected on indigenous bacterial population. Analysis of 16S rDNA clone showed that 68% of clones obtained during the experiment belonged to Proteobacteria Alpha or Beta. Terminal restriction fragment length polymorphisms (T-RFLP) analysis of PCR-amplified 16S rDNAs indicated that indigenous bacteria phylogenetically close to Nitrosomonas and Azoarcus group disappeared from the groundwater after the injection of strain KT-1. However, they were observed again as dominants after 18 days of pumping up.A statistical analysis, multi-dimensional scaling (MDS), was applied to the data of T-RFLP in order to evaluate the changes of bacterial populations. The results showed that indigenous bacterial populations perturbed by strain KT-1 were well restored in 51 days.
