Integrating Molecular and Biochemical Techniques to Characterize Adaptation Mechanisms of Anaerobic Microbial Communities Exposed to Chlorinated Organics.EPA Grant Number: R823351
Title: Integrating Molecular and Biochemical Techniques to Characterize Adaptation Mechanisms of Anaerobic Microbial Communities Exposed to Chlorinated Organics.
Investigators: Stahl, David A. , Rittmann, Bruce E.
Institution: Northwestern University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1995 through September 30, 1998
Project Amount: $406,372
RFA: Exploratory Research - Environmental Biology (1995) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Health , Ecosystems
Description:The primary focus of this research is to identify mechanisms of adaptation of anaerobic microbial communities exposed to chlorinated organics. Adaptation is defined here as any response of microorganisms to the presence of an initially recalcitrant compound that eventually results in measurable biotransformation of the compound. Newly developed molecular techniques are coupled with biochemical measurements so that adaptation, changes in community structure and diversity, and environmental changes can be correlated. Another related objective of this project is to develop a systematic approach to the application of molecular techniques, along with more traditional biochemical measurements, to the study of community adaptation mechanisms in general. An improved understanding of the mechanisms underlying the adaptation of anaerobic communities exposed to chlorinated aromatics should also provide insight into the mechanisms of reductive dehalogenation in mixed cultures.
These objectives will be accomplished in three stages of experiments. In the first stage, the adaptation of pristine anaerobic sediment communities to a number of chlorinated organics will be evaluated in order to identify degradable chlorinated substrates, estimate the lengths of adaptation periods in these systems, and determine sampling intervals for the second stage of experiments. 3-chlorobenzoate and 2-chlorophenol have been identified as substrates that could exhibit lengthy adaptation periods, and eventually biodegraded in pristine anaerobic sediment slurries. In the second stage of experiments, changes in community structure and function during adaptation to selected degradable chlorinated substrates will be systematically evaluated by measuring the concentrations of chlorinated substrates, H2, CH4, and various electron acceptors and by performing 16S rRNA-based hybridizations. In the third stage of adaptation experiments, community structure analyses will be refined in order to monitor population shifts within groups that appeared to be important during adaptation, and polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analyses will be applied to examine changing community and group diversity during adaptation.
The integrated experimental strategy used in this project should be applicable to and aid in the systematic design of other studies involving adaptation to recalcitrant compounds. In this way, the experimental evidence needed to conclusively evaluate the importance of various potential adaptation mechanisms can be obtained in these studies. Identification of the factors influencing the adaptation periods associated with chlorinated organics and other pollutants could be used to improve the engineering of bioremediation and waste stream treatment systems that receive these compounds in order to minimize delays in their biodegradation.