Screening of putative antimicrobials from Bacillus strauns isolated from bat guano in select karst areas of Rodriguez, Rizal

Date

2025

Adviser

Abriel S. Bulasag

Principal

Mabel S. Buela

Abstract

Bacillus species are known producers of antimicrobial compounds such as bacitracin, polymyxin, and surfactin, which have been widely studied for their efficacy against microbial pathogens. In light of rising antimicrobial resistance, these bioactive metabolites offer promising leads for the development of new antibiotics. While Bacillus strains have been extensively documented in terrestrial and marine environments, their antimicrobial potential from bat guano in karst caves remains underexplored. This study aimed to characterize the antimicrobial activity of Bacillus strains isolated from bat guano collected in the Pamitinan Protected Landscape, Rodriguez, Rizal, under the NICER CAVES Program of the University of the Philippines Museum of Natural History. Composite bat guano samples yielded seven isolates (1AT–7AT). Isolation was performed using serial dilution and streak plating, followed by Gram staining and microscopy for initial characterization. To identify the isolates at the molecular level, genomic DNA was extracted, and PCR amplification and partial sequencing were conducted. Gel electrophoresis was performed to confirm the size and integrity of the PCR products. BLAST analysis was used to determine genetic similarity, and MEGA 11 software was employed for phylogenetic analysis. Antimicrobial activity was screened using the cross-streaking method against four ESKAPE pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter ludwigii) and Escherichia coli, which was included as a model organism. None of the Bacillus isolates demonstrated antimicrobial activity against the tested pathogens. Despite this, the findings provide valuable insights into the microbial diversity of cave-derived Bacillus and emphasize the potential of karst ecosystems for future bioprospecting. Continued exploration of natural environments remains essential in the search for novel antimicrobial agents.

Language

English

Location

UP Rural High School

Notes

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Document Type

Capstone

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