Date of Award

8-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Lee H. Lee

Committee Member

Sandra D. Adams

Committee Member

John Gaynor

Abstract

Over the past couple of decades humans have been combating the problem of multi-drug resistant microorganisms. Multi-drug resistant strains o f microorganisms have been causing not only problems for medical settings, but the world as well. Because of the continuous use of antibiotics within our time and age, there has been a huge increase in antibiotic resistant bacteria. In addition to the rise in multi-drug resistant bacteria over time, endospore cells have been causing increased levels of food-bourne illnesses. Thus, there is a need for novel antimicrobial agents from nature derived products as an alternative way to treat and control these microorganisms. This specific study has been focused on the effects of green tea polyphenols (GTP) and a modified derivative, lipophilic tea polyphenol (LTP), Epigallocatechin Gallate (EGCG), and the modified derivative, Epigallocatechin Gallate - Stearate (EGCG-S) as antimicrobial agents against bio film formation and endospore germination. The selected bacteria for this study were the gram negative bacteria Pseudomonas aeruginosa and Pseudomonas fluorescens for the bio film study and the endospore forming bacteria Bacillus cereus, Bacillus megaterium, and Bacillus subtil is for the endospore study. For the bio film formation study, air-liquid interface assays, crystal violet assays, and Congo red assays were used to analyze the ability of the tested bacteria to form biofilm when treated with tea polyphenols. The results indicated that each of the tea polyphenols used in this research have strong inhibitory effects and LTP and EGCG-S had the strongest effects on inhibiting biofilm formation. Concentrations o f 50pg/mL-100pg/mL were enough to inhibit biofilm formation from both bacteria. The fluorescent and scanning electron microscopic observations suggested that tea polyphenols affect the cell surface integrity, which was shown by damaged bacteria cells when treated. For the endospore germination study, colony-forming unit (CFU) studies and time kill studies indicated that concentrations of LTP and EGCG-S at 1% and 5% treated for 15 minutes and up to 2 hours were both able to inhibit endospore germination up to 100%. Transmission electron microscope images suggested that the inhibitory effect of EGCG-S might be due to its ability to damage the endospore coat and cause agglutination of endospores. These results suggest the potential beneficial effects of using each tea polyphenol to work as a nature derived compound to inhibit biofilm formation and endospore germination. It can be concluded from these results that each of the polyphenols, GTP, LTP, EGCG, and EGCG-S, can be used as potential antimicrobial agents.

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