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theses

Iron reducing organisms are ubiquitous and phylogenetically diverse. Their acitivity in the environment not only affects the speciation of iron in aquatic systems or sediments, but it plays a major role in iron mineral formation, sediment diagenesis, carbon cycling and the fate and transport of contaminants in the subsurface environment. Iron oxide reduction has been extensively studied with pure cultures of dissimilatory iron reducers such as Geobacter and Shewanella. However, the effects of syntrophy on iron oxide reduction and secondary mineralization by microbial consortia are poorly understood. The research presented in this dissertation describes enrichment of an iron reducing anaerobic microbial consortium from subsurface sediments. The consortium was composed of fermentative Clostridium sp. strain FGH and a novel Veillonellaceae, strain RU4. The experimental results indicate the role of hydrogen, sulfate and growth medium in rapid reductive dissolution of iron oxides and subsequent secondary mineralization by the clostridial consortium. The data demostrated that iron oxide reduction by the consortium was catalyzed by both biotic reduction by strain FGH and syntrophy driven biotic/abiotic reduction by strain RU4. Reductive dissolution of iron oxides by the consortium resulted in formation of solid-phase Fe(II) and poorly crystalline ferrous bearing minerals such as nanoparticulate magnetite and iron sulfides. The results of this work provide new insights in the ecological role of Clostridia in subsurface Fe(II) mineral formation processes. Unlike iron respiring Geobacter and Shewanella, the mechanism of iron oxide reduction is poorly understood in iron reducing fermentative bacteria. In this study we conducted experiments with fermentative Clostridium sp. strain FGH to elucidate its mode of iron reduction. Experiments and genome analysis suggest an indirect, cytochrome c independent mechanism of iron reduction by strain FGH. Veillonellaceae are recently found to be active during bioremediation studies at contaminanted sites. Genomic characterization of the novel Veillonellaceae, strain RU4, that could not be isolated in pure culture revealed its potential metabolic capabilities. The strain RU4 draft genome consists of fatty acid metabolism genes and pathways for sulfate, sulfite and polysulfide reduction. These results may assist in better understanding of the biogeochemical and ecological role of this novel subsurface bacterium.

ETD_4662

Ph.D.

Includes bibliographical references

by Madhavi Shah

http://hdl.rutgers.edu/1782.1/rucore10001600001.ETD.000068966

doi:10.7282/T33R0RFJ

ETD doctoral

The author owns the copyright to this work.