Status : Verified
| Personal Name | Almalvez, James Ivan L. |
|---|---|
| Resource Title | Investigative studies on the Cr(VI) resistance and ChrA efflux pump of Magnetotactic bacteria Magnetospirillum gryphiswaldense (MSR-1) |
| Date Issued | 30 June 2026 |
| Abstract | Removal of hexavalent chromium has been a focus for studies in recent years due to its prevalence and toxicity. The use of magnetotactic bacteria in treating chromium-containing waters has been gaining interest due to its advantage of being able to be separated from the effluent, among other benefits of biological methods. Magnetospirillum gryphiswaldense (MSR-1) has already been proven to reduce Cr(VI) to less toxic Cr(III), but its resistance to the metal has not been studied. This study aims to elucidate the Cr(VI) resistance of MSR-1 by assessing its resistance limits and evaluating its efflux pump capabilities through heterologous expression in E. coli BL21. The minimum inhibitory concentration (MIC) of MSR-1 was found to be 3 mg Cr(VI)/L, although its magnetosome synthesis was already hindered at 2 mg Cr(VI)/L. MSR-1 was also found to be capable of surviving 14 cycles of 12-hour exposures to 10 mg/L of chromium without a significant impact on its average Cr(VI) reduction capacities, but the growth of magnetosome-deficient strains was observed. The engineered bacteria exhibited higher resistance and lower chromium uptake compared to the control, up to a concentration of 50 mg/L Cr(VI). The engineered strain recorded an 83.67% retention of intracellular chromium, indicating better efflux capabilities compared to the control strain’s 97.89% retention rate. However, increasing the culture concentration and duration led to a decrease in efflux capacities. Molybdate, vanadate, and NADPH inhibited the efflux of the engineered strain by 14.32%, 15.28%, and 23.82%, respectively. Conversely, the addition of valinomycin improved efflux by 34.26% |
| Degree Course | PhD Environmental Engineering |
| Language | English |
| Keyword | magnetotactic bacteria, ChrA, engineered bacteria, efflux, chromium resistance |
| Material Type | Thesis/Dissertation |
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