Date of Award

Spring 5-21-2022

Degree Type

Dissertation

Degree Name

PhD Molecular Bioscience

Department

Biology

Advisor

Tinchun Chu, Ph.D.

Advisor

Angela V. Klaus, Ph.D.

Committee Member

Daniel B. Nichols, Ph.D.

Committee Member

Gregory Wiedman, Ph.D.

Committee Member

Lee H. Lee, Ph.D.

Keywords

antibacterial; sporicidal; anti-germination; binding analysis; natural product; black tea polyphenol; theaflavin; biofilm; quorum sensing

Abstract

Black tea polyphenol theaflavin (TF) extracted from the leaves of Camellia sinensis has shown to have anti-inflammation, anti-cancerous, antioxidant, antibacterial, and antiviral effects. This study aims to determine the antibacterial, anti-spore, and antibiofilm properties of Theaflavin-3,3′-digallate (TFDG). The bacteria included in this study were: Gram-positive: Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogenes; Gram-negative: Klebsiella aerogenes, Escherichia coli, Pseudomonas aeruginosa, and Proteus mirabilis; and acid-fast Mycobacterium smegmatis. Through microplate assay, colony-forming unit (CFU), BacTiter-GloTM, and Live/Dead Assay, 250 µg/mL TFDG was able to inhibit up to 99.97% of bacterial growth, and 625 µg/mL TFDG was able to inhibit up to 99.92% of the spores from germinating after a one-hour treatment. Through Congo Red, Resazurin Assay, CFU, and Live/Dead Assay, 500 µg/mL TFDG was able to inhibit up to 99.55% biofilm formation, while 2000 µg/mL TFDG was able to reduce up to 88.51% of a pre-established biofilm. The in silico modeling for both germination proteins in Bacillus spp. and Pseudomonas aeruginosa QS protein reveals favorable binding affinity. Semi-quantitative RT-PCR showed that TFDG treatment lowered the expression of gpr, ranging from 0.20 to 0.39 compared to the control in both Bacillus spp. The results suggest that TFDG not only inhibits the growth of vegetative cells but also prevents the germination of bacterial spores. This study indicates that TFDG is a promising broad-spectrum antibacterial, anti-spore, and antibiofilm agent against Gram-positive, Gram-negative, acid-fast bacteria.

Available for download on Wednesday, May 05, 2032

Share

COinS