Adaptation of aquifer microbial communities to the biodegradation of xenobiotic compounds: Influence of substrate concentration and preexposure

Abstract

Studies were conducted to examine the adaptation response of aquifer microbial communities to xenobiotic compounds and the influence of chemical preexposure in the laboratory and in situ on adaptation. Adaptation and biodegradation were assessed as mineralization and cellular incorporation of 14C‐radiolabeled substrates. For some compounds, such as ethylene dibromide, aniline and m‐nitrophenol, biodegradation and adaptation rates were not influenced by chemical concentration over the range tested. Biodegradation rates increased with concentration for p‐chlorophenol, and a gradient of adaptation and biodegradation responses was observed for p‐nitrophenol up to a threshold concentration. Acclimation to laboratory conditions decreased but did not eliminate the adaptation period to p‐nitrophenol. Laboratory adaptation studies and examination of uncontaminated and contaminated field samples from a single aquifer indicated that adaptation was accompanied by shifts in the metabolic fate of the substrate. The increased metabolism associated with adapted communities was predominantly the result of increased mineralization. Cellular incorporation represented a significantly smaller fraction of total metabolism in the adapted versus the unadapted communities. The results indicate that the adaptation response in aquifer solids is due to a complex set of interactions that are influenced by the physiology and growth of the degrading populations.

Contrasts between subsurface microbial communities and their metabolic adaptation to polycyclic aromatic hydrocarbons at a forested and an urban coal-tar disposal site

“…Metabolic adaptation by subsurface microorganisms to environmental pollutants at field sites can be documented using two principal types of criteria: the response may be qualitative, i.e., metabolism may be present in contaminated samples and absent in adjacent uncontaminated samples [6,20,32,35], or the response may be quantitative, i.e., prior exposure of microorganisms to a pollutant may shorten the lag period prior to the onset of metabolic activity [1,2], increase the rate or extent of metabolism, or enhance the proportion of the pollutant that is respired [2]. The presence of a control site that is uncontaminated, adjacent to the contaminated groundwater plume, and whose microbial community exhibits either low or no contaminant metabolism is crucial for demonstrating adaptation.…”

“…and Traverse City, Michigan [2]. Although these settings represent a wide diversity of climatological, geologic, hydrologic, and other conditions, they all contained subsurface microbial communities that rapidly metabolized contaminant compounds inside but not outside the plume of contaminated groundwater.…”

“…The operational definition of metabolic adaptation is well established: microbial metabolism of specific organic compounds is accelerated by prior exposure to the compounds [15,22,35]. Numerous investigations [1,2,6,20,32,35] have reported that subsurface samples from plumes of contaminated subsurface material were active in mineralizing organic compounds in microcosms, whereas mineralization of the same compounds by samples of adjacent uncontaminated samples was either low or absent. Likewise, exposure of uncontaminated subsurface samples of aquifer material to pollutant compounds in laboratory experiments has also been shown to accelerate microbial metabolism of the pollutant compounds in the material [2,29,30].…”

Variation of bacterial community immobilized in polyethylene glycol carrier during mineralization of xenobiotics analyzed by TGGE technique

“…The low biodegradability of xenobiotics may be due to the incapacity of microorganisms to effectively metabolize the organic compounds with uncommon chemical structures or properties; however, the microbial ability for the biodegradation of xenobiotics can be improved biologically by enrichment culture or adaptation to the specific organic compounds [3]. The time required for a bacterial community to mineralize xenobiotics and the concentration of xenobiotics may be a critical factor for determining degradation efficiency in wastewater treatment reactor [4,5]. Especially, the difference of persistence and initial concentration among xenobiotics contained in wastewater may be an important determinant for maintenance of bacterial community and biodegradability of individual xenobiotic [6][7][8].…”

Influence of Wood Biochar on Phenanthrene Catabolism in Soils

“…Indeed, microbial degradation is a major loss pathway for PAHs from soil [1,2]. The ability of microbes to adapt to PAHs and the time required for adaptation to occur, in part, determines the persistence of organic contaminants [3]. For example, Johnson and Karlson [4] showed that previous exposure to PAHs at levels greater than background levels influenced adaptation and the ability of the indigenous microbes to degrade PAHs.…”