| Anaeromyxobacter dehalogenans is the first member of myxobacteria found to be able to grow anaerobically. Previous studies identified its ability to respire chlorophenol, nitrate, nitrite, fumarate, and oxygen and obtain energy for growth. This provides unusual opportunities to study chlororespiration in parallel with other respiration processes using the same microorganism. The objectives of this research were to characterize in more detail the physiology of A. dehalogenans and to uncover the mechanisms of acetotrophic respiration.; Findings from this research identified the exceptional dechlorination ability of A. dehalogenans (116 mumol Cl- ·mg protein-1·h-1 ), and led to the discovery of its potential to couple growth to the reduction of heavy metals (Fe(III) and U(VI)), indicating a possible benefit of using these organisms for environmental clean-up. The ability of these organisms to successfully compete for nanomolar level acetate as the electron donor, in contrast to micromolar level required by methanogens, suggests that A. dehalogenans will successfully compete in environmental systems. The inability to use sub-nanomolar level acetate in chlororespiration, however, is attributed to the requirement for auxiliary energy to alleviate the toxicity of chlorophenols. Furthermore, the distinctive ability of A. dehalogenans to oxidize acetate in anaerobic respiration with diverse electron acceptors was investigated using biochemical and molecular approaches. Biochemical studies revealed characteristic components of acetotrophic respiration, such as the involvement of a c-type cytochrome. Representational difference analysis of cDNA further identified novel genes differentially expressed under chlororespiring conditions which will facilitate the identification of the specific proteins involved. Finally, the ecological importance of these organisms continues to grow as indicated by our and others' isolation of closely related organisms from different environmental samples. With a broad global distribution, A. dehalogenans serves as an ideal candidate for studying both biostimulation and bioaugmentation remediation technologies. Findings of this research lay the groundwork for future studies of A. dehalogenans in the bioremediation of mixed contaminants and for obtaining a fundamental understanding of the underlying biological principles. |
