Heavy metal tolerance of isolated gram-positive bacteria from selected sites of Pasig River

• Main Authors: Galang, Maria Gianna Mikayla B., Gironella, Ella marie G., Kahayon, Angelica Mae M.
• Format: text
• Language: English
• Published: Animo Repository 2016
• Subjects: Poisons > Philippines; Bacteria > Philippines; Water > Philippines; Heavy metals > Philippines; Pasig River (Philippines)
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/9658
• Institution: De La Salle University

The study focused on determining the tolerance to heavy metals of the isolated gram-positive bacteria from selected sites of Pasig River (Intramuros, Manila; Sta. Mesa, Manila; and Pinagbuhatan Pasig. Water samples were collected from three (3) different sites established within Pasig River and were first analyzed for the presence of different heavy metals. After the sample collection from the three (3) different sites, 15 gram-positive bacteria were obtained for Site 1, 16 gram-positive bacteria for Site 2, and 22 gram-positive bacteria for Site 3, which were isolated and utilized for this study. The isolates were first screened through gram-staining and were described by means of colonial morphological characterization, and biochemical tests (Blood Agar Plate Method, Catalase Test, Coagulase Test, and Mannitol Salt Agar Plate Method). Their ability to tolerate heavy metals, specifically Nickel Chloride (NiCl2) and Lead Nitrate (Pb(NO3)2), was tested through Agar Plate Assay, that involves the inoculation of the bacteria to different concentrations of heavy metal (0.25-g/L, 0.5-g/L and 1.0-g/L). The tolerance of the gram-positive isolates to NiCl2 at all concentrations was high, which was 5 out of 15 (33%) isolates for Site 1, 8 out of 16 (50%) isolates for Site 2, and 9 out of 22 (41%) isolates for Site 3. In addition, the results of Pb(NO3)2 was lower, which was 4 out of 15 (27%) for Site 1, 4 out of 16 (25%) isolates for Site 2, and 6 out of 22 (27%) isolates for Site 3. The results support the significance of NiCl2 to the cellular processes of bacteria, as compared to Pb(NO3)2, which is known for its toxic effects when exposed to microorganisms. However, some isolates were unable to grow at the presence of higher concentration of NiCl2 and in some cases, all concentrations of Pb(NO3)2. This may be due to the concentration of the heavy metal which was higher than the normal standard value or it may also be due to the site where it is located which may not contain high levels of these toxic substances that hinder the possibility of the bacteria to develop adaptive mechanisms for heavy metal tolerance. The findings of this study were able to prove the capacity of the gram-positive bacteria in the three (3) sites of Pasig River with regard to tolerating heavy metals at different concentrations. Lastly, some of these isolates were considered pathogenic based on their biochemical test results which could bring more harm, making them not suited for bioremediation.