Graduation Year


Date of Submission


Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts



Reader 1

Aaron Leconte

Reader 2

Ethan Van Arnam

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Terms of Use for work posted in Scholarship@Claremont.

OCLC Record Number



Bacteria secrete and sense extracellular signals from neighboring members of a colony in a phenomenon called quorum sensing. These signals vary from species to species but allow for changes in the behavior of a colony based on changes to cell density, environment, or nutrient supply. Of particular interest to human health is the quorum sensing system of Streptococcus pneumoniae as this pathogen accounts for around one million infection-related deaths per year and is difficult to combat largely due to its ability to form biofilms. These polysaccharide coverings protect entire bacterial colonies from antimicrobial agents as well as allow them to adhere well to the nasopharynx passages of organisms, making them hard to remove. To gain a better understanding of quorum sensing in S. pneumoniae, we propose experiments to study its biofilm formation and its interactions with black carbon, a biochar shown previously to interact with the quorum sensing systems of related bacteria species. We hypothesize that inhalation of black carbon will aggravate a S. pneumoniae infection by promoting biofilm-forming quorum sensing systems making it easier for this bacteria to adhere to and remain on mammal lungs. We propose to first explore the competency and biofilm quorum sensing systems in S. pneumoniae to identify any shared signals between the two using RT-PCR and FITC-Dextran experiments. Further experiments will analyze black carbon particles’ effects on bacterial colonies grown on plates and present on the lung linings of mammals.

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.