Adaptation of Natural Microbial Communities to Degradation of Xenobiotic Compounds: Effects of Concentration, Exposure Time, Inoculum, and Chemical Structure

Abstract

Adaptation of microbial communities to faster degradation of xenobiotic compounds after exposure to the compound was studied in ecocores. Radiolabeled test compounds were added to cores that contained natural water and sediment. Adaptation was detected by comparing mineralization rates or disappearance of a parent compound in preexposed and unexposed cores. Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure. Adaptation was maximal after 2 weeks and was not detectable after 6 weeks. A threshold concentration of 10 ppb (10 ng/ml) was observed; below this concentration no adaptation was detected. With concentrations of 20 to 100 ppb (20 to 100 ng/ml), the biodegradation rates in preexposed cores were much higher than the rates in control cores and were proportional to the concentration of the test compound. In addition, trifluralin, 2,4-dichlorophenoxyacetic acid, and p-cresol were tested to determine whether preexposure affected subsequent biodegradation. Microbial communities did not adapt to trifluralin. Adaptation to 2,4dichlorophenoxyacetic acid was similar to adaptation to nitrophenol. p-Cresol was mineralized rapidly in both preexposed and unexposed communities.

Biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons by a wood-degrading consortium at low temperatures

“…In contrast to previous works (Spain & VanVeld, 1983;Johnsen & Karlson, 2005), consortium BOS08 did not require pre-exposure to PAHs to induce microbial adaptation and consequently degradation of those pollutants.…”

MINERALIZATION AND SORPTION OF p-NITROPHENOL IN ESTUARINE SEDIMENT

“…These results were based on degradation in river water and on concentrations of up to 20 mg/L p-nitrophenol. Earlier studies of p-nitrophenol degradation in coastal sediments indicated that sediment preexposure affects the rate of degradation of the compounds by the sediment on reexposure [6,7]. p-Nitrophenol has been listed as priority pollutant by the U.S. Environmental Protection Agency.…”

Adaptation to a Quaternary Ammonium Surfactant by Suspended Microbial Communities in a Model Stream

“…Pritchard et al [19] observed that adaptation to methyl parathion by salt-marsh organisms required continuous exposure to the chemical. Spain and Van Veld [20] observed that the ability of microbial communities to degrade p-nitrophenol declined as the chemical disappeared from static microcosms. The researchers suggested that adaptation could possibly be maintained by "priming" microbial communities with small doses of test chemical but that some periodic exposure was necessary.…”