K.N. Timmis | Geology Reports

USGS2002

Behavior of pollutant-degrading microorganisms in aquifers: Predictions for genetically engineered organisms

Bioremediation via environmental introductions of degradative microorganisms requires that the microbes survive in substantial numbers and effect an increase in the rate and extent of pollutant removal. Combined field and microcosm studies were used to assess these abilities for laboratory-grown bacteria. Following introduction into a contaminated aquifer, viable cells of Pseudomonas sp. B13 were present in the contaminant plume for 447 days; die-off was rapid in pristine areas. In aquifer microcosms, survival of B13 and FR120, a genetically engineered derivative of B13 having enhanced catabolic capabilities for substituted aromatics, was comparable to B13 field results; both bacteria degraded target pollutants in microcosms made with aquifer samples from the aerobic zone of the pollutant plume. Results suggest that field studies with nonrecombinant microorganisms may be coupled to laboratory studies with derivative strains to estimate their bioremediative efficacy. Furthermore, laboratory strains of bacteria can survive for extended periods of time in nature and thus may have important bioremediative applications.

Environmental Science & Technology↗

USGS1993

Degradation of trichloroethylene by Pseudomonas cepacia G4 and the constitutive mutant strain G4 5223 PR1 in aquifer microcosms

Pseudomonas cepacia G4 degrades trichloroethylene (TCE) via a degradation pathway for aromatic compounds which is induced by substrates such as phenol and tryptophan. P. cepacia G4 5223 PR1 (PR1) is a Tn5 insertion mutant which constitutively expresses the toluene ortho -monooxygenase responsible for TCE degradation. In groundwater microcosms, phenol-induced strain G4 and noninduced strain PR1 degraded TCE (20 and 50 μM) to nondetectable levels (< 0.1 μM) within 24 h at densities of 10 8 cells per ml; at lower densities, degradation of TCE was not observed after 48 h. In aquifer sediment microcosms, TCE was reduced from 60 to < 0.1 μM within 24 h at 5 x 10 8 PR1 organisms per g (wet weight) of sediment and from 60 to 26 μM over a period of 10 weeks at 5 x 10 7 PR1 organisms per g. Viable G4 and PR1 cells decreased from approximately 10 7 to 10 4 per g over the 10-week period.

Applied and Environmental Microbiology↗