Researcher ORCID Identifier

0009-0003-9580-5687

Graduation Year

2023

Date of Submission

4-2023

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Pete Chandrangsu

Reader 2

Aaron Leconte

Abstract

Antimicrobial resistance is a large problem today as microbes find new ways to evade antimicrobials. Thus, it is necessary to understand how microbes can evolve to escape these systems. Here, we use experimental evolution, genetics, and biochemistry to understand how the model Gram-positive bacterium, Bacillus subtilis, develops resistance to copper, a known antimicrobial. Copper is known to cause damage to cells through a recently discovered concept called contact killing but has been used for its antimicrobial properties for centuries, dating back to early Egyptian texts. Genome sequencing revealed that all mutants that survived on high copper concentrations had a mutation in the ppsB gene, leading to a loss of plipastatin synthetase. Plipastatin is an antibacterial compound and helps protect the bacterium from competing bacteria and fungi. In conclusion, loss of ppsB leads to a greater ability of B. subtilis to grow in increasing copper concentrations and future research will evaluate whether plipastatin is shuttling copper into the cell or changing the form of copper, including an investigation into the same B. subtilis mutant strain in a low copper concentration environment. These findings may be important in potentially identifying plipastatin as a chalkophore.

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

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