Screening Of Antibacterial Activity Of Soil-Isolated Microorganisms From Mangrove Forests Of Bataan, Pangasinan, And Quezon Provinces
Background: Antibiotics can be loosely defined as a variety of substances derived from bacterial sources that control the growth of or kill other bacteria. However, through the course of time and with improper utilization, the issue of antimicrobial resistance has emerged creating concerns in the field of medicine and research. This has urged researchers to find new ways of developing an antibiotic that can be functional in our time. Actinomycetes is a major source of novel bioactive compounds and therapeutically and clinically relevant antibiotics. Neglected habitats, such as mangrove forests, have proven to be a good source of Actinomycetes. The aim of the study was conducted to screen and isolate potential antibiotic producing bacteria from saprophytic soils collected from Samal Bataan, Lucena Quezon, and Mangaldan Pangasinan, Philippines.
Methods: Three random soils from the expanse of the mangrove forests were collected and stored in a sterile container. One gram of soil was mixed with 9 mL Phosphate Buffer Solution and was subjected to serial dilution (1:10). The soil in the last tube with a dilution of 1:100000 was planted on Nutrient Agar plates using the crowded plate technique. Colonies that showed clear zones of inhibition were further subcultured producing pure colonies. The pure isolates were tested for antagonism against the following test organisms: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Bacillus subtillis and Pseudomonas aeruginosa.
Results: The isolate was subjected to physical identification of morphological features and Gram Staining. Microscopic results showed gram-positive bacilli under oil immersion objective. The isolate was tested on five test organisms namely S. aureus, E. coli, K. pneumoniae, P.aeruginosa, and B. subtilis. Significant inhibition was seen on 2 of 5 test microorganisms namely S. aureus and E. coli. The isolate (PBS5) was diluted and compared to the McFarland standard for the VITEK 2 identification. This gave biochemical results and identification of Streptomyces griseus.
Conclusion: The study produced an isolate with antibacterial activity against S. aureus and E. coli. PBS5 isolate was identified to be Streptomyces griseus under the order Actinomycetales.
Keywords- Actinomycetes, soil-isolated microorganisms, antimicrobial activity