Graduation Year

2026

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Jason Tor

Reader 2

Pete Chandrangsu

Abstract

Abstract

Antibiotic-resistant bacteria have been a threat since the discovery of antibiotics. The increased rise of antibiotic-resistant bacteria has created an immediate need for new antibiotics. Violacein, a purple bisindole pigment produced by Janthinobacterium lividum, has been shown to be a promising new antibiotic. Its efficacy has not been completely demonstrated, and this project aims to further investigate the effectiveness of violacein as an antibiotic. To do this, a minimum inhibitory concentration (MIC) test was conducted. Violacein was grown, extracted, purified, and tested across concentrations ranging from 1.0 to 500.00 µg/mL to cover values well above and below previously cited MIC values. Violacein was tested against two test species, the gram-negative E. coli and the gram-positive S. epidermidis. It was hypothesized that violacein would have a stronger effect on S. epidermidis than E. coli, as it is gram-positive and does not have an outer cell membrane. Results showed that E. coli had no measurable response to violacein. At concentrations of 125.0 to 500.0 µg/mL, S. epidermidis did exhibit reduced growth. However, violacein was not able to fully inhibit growth for either test species. These results contrast with previous research and suggest that violacein has a variable antibiotic effect. Further investigation into the extraction methods and variable effects of violacein are needed to fully assess its clinical potential.

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