You are here:
AQUIFER PROTIST RESPONSE AND THE POTENTIAL FOR TCE BIOREMEDIATION WITH BURKHOLDERIA CEPACIA G4 PR1
Citation:
Snyder, R. A., W. S. Steffensen, S. C. Enfinger, AND J. Millward. AQUIFER PROTIST RESPONSE AND THE POTENTIAL FOR TCE BIOREMEDIATION WITH BURKHOLDERIA CEPACIA G4 PR1. MICROBIAL ECOLOGY 40(3):189-199, (2000).
Description:
The introduction of bacteria into the environment for bioremediation purposes (bioaugmentation) requires analysis and monitoring of the persistence and activity of microbial population for efficacy and risk assessment purposes. Burkholderia cepacia G4 PR123 and PR131 constitutively express a toluene ortho -monooxygenase (tom) due to a secondary transposition of a Tn5 mutation in a trichloroethylene (TCE) degradative plasmid (TOM). This bacterium is of interest for bioremediation of TCE contaminated aquifers. Both ground water and sediment from a potential release site have been used in laboratory microcosms to define the factors that limit survival of this organism prior to field release. A nucleic acid sequence detection assay has been developed for the plasmid being released targeting the IS50R insertion site with a limit of detection of 1 x 103 cells ml-1 of aquifer sediment slurry and 1 x 102 cells ml -1 in groundwater. In sterile systems, PR1 maintains stable populations for extended periods. In non-sterile systems however, the bacterium is eliminated concomitant with an increase in bacterivorous protists. The half life for the organism in non-sterile systems increases logarithmically with increasing initial inoculation density about 1 x 106 PR1 ml-1. Below this level of inoculation, the half life of PR1 increases with decreasing inoculation density. The inflection point for this response with the lowest half lives estimated corresponds to the threshold for numerical (growth) response of the native bacterivores. In column systems designed to mimic aquifer flow, repeated pulses of PR1 result in a build up of bacterivore populations reducing the half life of the bacterium for subsequent additions. Addition of 0.5 |M TCE in the elution stream results in prolonged survival of PR1, presumably from toxic effects on bacterivorous protists. No PR1-specific viruses could be isolated from the target environment. The results suggest that abiotic factors are not limiting to the bacterium in the target aquifer, but rapid losses from native bacterivores will occur beyond a treatment zone where contaminant toxicity may limit their activity.