Date of Award


Degree Type


Degree Name

Master of Science (MS)


Microbiology and Immunology


Bacillus subtilis is a probiotic bacterium that can protect against the murine-

specific attaching and effacing (A/E) pathogen Citrobacter rodentium. C. rodentium displays many features observed with the human pathogen enteropathogenic E. coli (EPEC). Protection by B. subtilis is mediated by exopolysaccharide (EPS), which is encoded by the epsA-O operon that contains 15 genes. Disruption of one of these genes, epsH, which appears to encode a putative glycosyltransferase, leads to the loss of protective capacity by B. subtilis and by EPS. EPS is a major component of the B. subtilis biofilm and the ΔepsH mutant is unable to form a biofilm. The goal of this project was to characterize EPS produced by B. subtilis with mutations to the 15 genes of the epsA-O operon and assess how single deletions to the genes affect phenotype (biofilm formation), and the capacity to protect mice from disease caused by C. rodentium. We found that mutations in 13 of the 15 genes eliminated the probiotic activity of B. subtilis, even though some of the mutants developed biofilms. Our goal is to compare the structures of EPS from protective and non-protective mutants, and identify a small molecule that can be used as a therapeutic to prevent disease caused by enteropathogens.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.