Previous research discovered the existence of sedimentation-resistant mutants of E. coli. Genomic studies revealed that these mutants resisted sedimentation due to independent modifications to genes that influenced the Rcs signal transduction pathway, causing increased secretion of an exopolysaccharide capsule comprised primarily of colanic acid. The Rcs system is responsible for detecting envelope stressors; consequently, ampicillin and osmotic stress were used to perturb the cellular envelope and study the response of the mutants compared to wild-type cells. It was found that the overproduction of colanic acid in the mutants confers some resistance to envelope stress; however, the mutants still behaved similarly to wild-type cells. The doubling times of the strains grown in sodium chloride solutions were calculated. A wavelength scan from 400 nm to 800 nm was performed on strains grown in different salt concentrations to determine if there were significant differences in light scattering between the wild-type and mutant cells. Further analysis was performed that, along with the doubling time data, suggested that wild-type cells may have turned on genes for capsule production in response to being grown in high salt concentrations. Additional research could be conducted to test this hypothesis, perhaps through the quantification of colanic acid through a methyl pentose assay for wild-type cultures grown with high salt concentrations. The idea that wild-type cells could digest colanic acid as a carbon source when lacking resources was also investigated with different preparations of colanic acid. One preparation of colanic acid showed promising results, which could indicate that bacteria are able to digest their capsule in a novel method to produce energy when starved. Again, additional investigation should be conducted to confirm these results. Other future experiments could study the metabolome of these mutants to determine if they have increased quantities of alarmones related to biofilm formation.

Thesis Completion




Thesis Chair/Advisor

Moore, Sean D.


Bachelor of Science (B.S.)


College of Medicine


Burnett School of Biomedical Sciences



Access Status

Open Access

Release Date