Research Product

The introduction of bacteria into aquifers for bioremediation purposes requires monitoring of the persistence and activity of microbial populations for efficacy and risk assessment purposes. Burkholderia cepacia G4 PR1 constitutively expresses a toluene ortho-monooxygenase (tom) that aerobically mineralizes TCE. Groundwater and sediment from a potential release site have been used in laboratory microcosms to develop predictive models for the response of this organism. In sterile systems, PR1 maintains stable populations for extended periods. In non-sterile systems, the bacterium is eliminated concomitant with an increase in bacterivores. The half life for the organism in non-sterile systems increases logarithmically with increasing initial inoculation density above 1 x 106 PR1 ml-1. Below this level of inoculation, the half life of PR1 increases with decreasing inoculation density. The inflection point corresponds to a numerical response threshold for bacterivores. In column systems designed to mimic aquifer flow, repeated pulses of PR1 build up bacterivore populations reducing the half life of the bacterium for subsequent additions. Addition of 0.5 µmM TCE in the elution stream results in prolonged survival of PR1. The results suggest that abiotic factors are not limiting to the bacterium in the target aquifer, but rapid losses from native bacterivores will occur.