Date of Publication

7-2025

Document Type

Bachelor's Thesis

Degree Name

Bachelor of Science in Biology major in Medical Biology

Subject Categories

Microbiology

College

College of Science

Department/Unit

Biology

Thesis Advisor

Esperanza C. Cabrera

Defense Panel Chair

Mariquit M. De Los Reyes

Defense Panel Member

James Christopher C. Chua
Florabelle D. Querubin

Abstract (English)

Antimicrobial resistance (AMR) continues to rise globally due to the widespread and inappropriate use of antimicrobials. Quorum-sensing (QS) inhibition, which disrupts bacterial QS without exerting positive selective pressure for resistant strains to survive and be disseminated, offers a promising alternative. This study investigated the QS-modulating effects of the ethanolic Ficus septica leaf extract on extended-spectrum β-lactamase (ESBL)-producing Escherichia coli PGH168 isolate. The QS inhibition effect of the extract was first tested on Chromobacterium violaceum ATCC 12472, a model for the detection of QS interference activities. The extract did not inhibit the violacein pigment in C. violaceum, indicating no effect on acyl-homoserine lactone (AHL)-based QS. In E. coli PGH168, the extract inhibited both swimming and swarming motility, but enhanced biofilm formation, a combination characteristic of AI-2 (autoinducer 2)-mediated QS activation during biofilm maturation. These phenotypes align with flhDC repression and csgD activation, promoting curli fiber production and the transition to a sessile lifestyle, a characteristic of biofilm formation. This suggests that the extract acts not as a QS inhibitor, but as an AI-2 agonist through mimicry of the native AI-2 signal. AI-2 mimicry occurs when non-bacterial molecules activate the LuxS/Lsr system by resembling or functionally substituting for AI-2. Phytochemicals in F. septica may therefore mimic AI-2, triggering QS responses that shift E. coli PGH168 toward biofilm formation. These results contrast with previous studies reporting anti-biofilm activity in other Ficus species, likely due to species-specific phytochemicals or context-dependent QS interactions. In conclusion, data showed that F. septica extract induced a shift in E. coli PGH168 from motility to a sessile, biofilm-forming state, via AI-2 pathway activation, highlighting the potential role of plant-derived compounds as QS agonists in a context-dependent manner. This study presents the first documented evidence of the QS-inducing activity of F. septica on ESBL-producing E. coli.

Abstract Format

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Abstract (Filipino)

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Abstract Format

html

Language

English

Format

Electronic

Keywords

Beta lactamases; Escherichia coli; Quorum sensing (Microbiology)

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Embargo Period

8-12-2026

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Available for download on Wednesday, August 12, 2026

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