The Biochemistry and Molecular Biology of Microbial Selenate and Arsenate Transformation

EPA Grant Number: R826105
Title: The Biochemistry and Molecular Biology of Microbial Selenate and Arsenate Transformation
Investigators: Stolz, John F. , Oremland, Ronald S. , McCormick, Joseph
Current Investigators: Stolz, John F.
Institution: Duquesne University , United States Geological Survey [USGS]
Current Institution: Duquesne University
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1997 through September 30, 2000
Project Amount: $273,119
RFA: Exploratory Research - Environmental Biology (1997) RFA Text |  Recipients Lists
Research Category: Biology/Life Sciences , Aquatic Ecosystems


The mobilization of toxic elements and heavy metals in the environment can be strongly influenced by microbial activity. Sulfurospirillum barnesii, a strict anaerobic bacterium, has the ability to couple the oxidation of organic matter to the reduction of selenate and arsenate, compounds which have become significant environmental toxins. The hypothesis to be tested is that S. barnesii has separate pathways for arsenate and selenate reduction but that the selenate reductase is a less substrate-specific enzyme, capable of reducing a wide range of substrates. The objective of this proposal is to purify and characterize (Km, Vmax, substrate specificity, absorption spectrum, mid-point potential) the two reductases and associated cytochromes, and develop biochemical and molecular probes based on the selenate reductase that can be used to detect S. barnesii in nature. The probes will also be used to determine the relatedness of selenate reductases from other bacterial species.


The selenate reductase will be purified by preparative gel electrophoresis. Antibodies will be raised against the holoenzyme and used as the biochemical probe. The genes encoding the major subunits of the selenate reductase will be cloned and sequenced. Oligonucleotide probes and PCR primers will be designed from the sequence and tested for their efficacy to detect S. barnesii in natural samples.

Expected Results:

The results of this work will further our understanding of the biochemical mechanism of microbial reduction of selenium and arsenate by anaerobically respiring microbes. It will provide diagnostic tools for use in assessing the role of S. barnesii, and related species, in the mobilization of these toxic compounds in natural environments. This final aspect should help in developing better models for predicting the fate of selenium exyanions and their impact on biological systems.

Publications and Presentations:

Publications have been submitted on this project: View all 12 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 5 journal articles for this project

Supplemental Keywords:

heavy metals, ecology, soil, sediment, water, enzymes, indicators, bioremediation., Scientific Discipline, Waste, Ecosystem Protection/Environmental Exposure & Risk, Environmental Microbiology, Fate & Transport, Biochemistry, Bioremediation, Ecological Risk Assessment, Molecular Biology/Genetics, microbiology, microbial selenate, fate and transport, aerobic degradation, biodegradation, arsenate compounds, oligonucleotide probes, biotechnology, reductases, sulfurospirillum barnesii, oligobacteria, heavy metals

Relevant Websites: EPA icon

Progress and Final Reports:

  • 1998
  • 1999 Progress Report
  • Final Report