THE ROLE OF FERRIC IRON UPTAKE REGULATOR (FUR) PROTEIN ON IRON REGULATION IN COXIELLA BURNETII
Coxiella burnetii is a gram negative, obligate intracellular bacterium. It is the etiologic agent of Q fever in a variety of species including livestock, humans and arthropods. The bacterium infects the monocytes of its host and is encapsulated in the phagolysosome, an acidic vacuole meant to kill the bacterium, where it survives and replicates. C. burnetii must be able to acquire all the nutrients necessary for survival within this acidic environment. In all but one species of bacteria, iron has been shown as necessary for replication as is serves as a cofactor for many cellular processes. However, iron concentration must be maintained as a delicate balance. Too little iron and replication is impeded, while too much iron initiates the production of oxygen radicals which are fatal to the cell. Ferric iron Uptake Regulator (Fur) is responsible for the regulation of iron acquisition genes in many gram negative bacteria. Fur acts as a transcriptional repressor of iron regulated genes. These genes have a sequence within their promoter region called the “Fur box” that binds to the Fur protein when the protein is also bound to its co-repressor, Fe2+. In E. coli, Fur has been found responsible for the regulation of over 30 genes. Previous work showed that C. burnetii has a functional fur gene. We hypothesize that C. burnetii genes that contain promoters with a highly conserved consensus sequence are part of a Fur regulon. Our goal is to characterize this regulon. Nineteen putative Fur boxes were identified in C. burnetii. Fifteen of these were cloned into the pBlue plasmid expressing beta-galactosidase. These plasmids were then co-transformed with a plasmid expressing Fur into an E.coli fur deletion strain. The ?-galactosidase assay was then used to test promoter activity. Eleven of these promoters were evaluated. Three promoters, for open reading frames CBU0970, CBU0769 and feoB were found to be repressed in the presence of iron. We predict that although a Fur regulon is present in C. burnetii, it includes only a limited set of genes.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:fur coxiella iron regulation
Date of Publication:08/16/2006