Pre-Exposure Pristine and Contaminated Environments

These results are consistent with previous evidence (Fulthorpe et al. 1996) from a study of pristine soils that although populations existed that could degrade both 3-chlorobenzoate 

Degradation of contaminants may occur with bacteria that have been isolated from pristine environments without established exposure to the contaminants, and exhibit no dependence on substrate concentration. For example, organisms from a previously unexposed forest soil were able to degrade 2,4,6-trichlorophenol at concentrations up to 5000 ppm, and terminal restriction fragment length polymorphism analysis revealed that at concentrations up to 500 ppm, the bacterial community was unaltered (Sanchez et al. 2004). 

Experiments using marine sediment slurries have examined the effect of pre-exposure to various aromatic hydrocarbons on the rate of subsequent degradation of the same, or other hydrocarbons. The results clearly illustrated the complexity of the selection process for example, whereas pre-exposure to benzene, naphthalene, anthracene, or phenanthrene 

In experiments using soil samples from a pristine aquifer exposed in the laboratory to a range of compounds, the following widely diverse responses were observed (Aelion et al. 1987, 1989)  

Systematic studies on the degradation of 4-nitrophenol (Spain et al. 1984) showed that the rates of adaptation in a natural system were comparable to those observed in a laboratory test system and were associated with an increase in the number of degrading organisms by up to 1000-fold. 

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