Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Eric Gilbert

Second Advisor

Phang Tai

Third Advisor

John Houghton


B. anthracis alters its virulence gene expression profile in response to a number of environmental signals, including levels of bicarbonate and CO2. Virulence plasmid pXO1 is important to Bacillus anthracis pathogenicity as it carries the genes encoding the anthrax toxin and virulence regulatory factors. Induction of toxin and other virulence genes requires the pXO1-encoded AtxA regulatory protein. The cytochrome c maturation system influences the expression of virulence factors in Bacillus anthracis. B. anthracis carries two copies of the ccdA gene, encoding predicted thiol-disulfide oxidoreductases that contribute to cytochrome c maturation. Loss of both ccdA genes results in a reduction of cytochrome c production, an increase in virulence factor expression, and a reduction in sporulation efficiency. pXO1 also carries a gene encoding an Hfq-like protein, pXO1-137. Loss of pXO1-137 results in significant growth defects and reductions in toxin gene expression only when grown under toxin inducing conditions. Similarly, loss of a small RNA on pXO1, sRNA-1, results in similar growth defects and reductions in toxin gene production. Both increased and decreased expression of pXO1-137 and sRNA-1 result in growth defects suggesting narrow functional set points for Hfq and sRNA levels.