Superfund Research Program
Distribution of Microorganisms in Biofilms Surrounding Soil Particles
In-situ bioremediation procedures have the potential to provide cost-effective alternatives to the remediation strategies currently applied at Superfund hazardous waste sites. However, the development of effective bioremediation procedures depends on understanding of the behavior of the degradative microorganisms, which, under most conditions, exist as biofilms surrounding soil particles. Biofilms are complex ecosystems and their role in the natural environment needs to be better defined.
Scientists at the University of Cincinnati (UC) have developed a full suite of microelectrodes to quantify dissolved oxygen, pH, ammonium, nitrate, sulfide, and redox potential profiles in biofilms. The researchers are using these microelectrodes, in concert with molecular probes and confocal scanning laser microscopy, to investigate the locations of specific microorganisms in the biofilm and evaluate the biodegradative activity of the microorganisms.
These studies have led to a new understanding of the structure and function of microbial biofilms. Originally, biofilms were thought to be relatively homogeneous with respect to the spatial distribution of different microorganisms and the metabolic activity of those organisms. Recently, the UC research team has demonstrated that biofilms have a heterogeneous structure. They have shown that biofilms may be stratified, with an aerobic layer overlying anoxic or anaerobic layers. Biofilms may contain different combinations of microbial metabolic processes including aerobic oxidation, nitrification, denitrification, sulfate reduction, and methanogenesis. This heterogeneity has an impact on the availability of nutrients and the degradative capacity of the biofilm. As a result, models that describe biofilm function have been revised.
Incorporation of this new view of biofilm structure and function has led to the development of more efficient and effective biofilms for application in bioremediation strategies. This new understanding of biofilms has been applied to the operation of the biotower in the North Central Waste Water Treatment Plant near Dayton, Ohio. The improvement in effectiveness of the bioremediation process in this plant suggests that similar applications to Superfund site clean-up have the potential to dramatically improve bioremediation outcomes in those settings as well.
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To learn more about this research, please refer to the following sources:
- Palisdottir G, Bishop PL. 2000. From Microelectrodes and Gene Probes to Full-scale Nitrifying Plants. In: Biofilms in Wastewater Treatment: An Interdisciplinary Approach. IWA Publishing, London, United Kingdom.
- Bishop PL, Yu T. 1999. A microelectrode study of redox potential change in biofilms. Water Sci Technol 39(7):179-185.
- Ebihara T, Bishop PL. 1999. Biofilm structural forms utilized in bioremediation of organic compounds. Water Sci Technol 39(7):203-210.
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