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Interference of manganese removal by biologically-mediated reductive release of manganese from MnO_x(s) coated filtration media.

ABSTRACT: Discontinuing application of pre-filter chlorine is a common water treatment plant practice to permit a bioactive filtration process for the removal of soluble Mn. However, soluble Mn desorption has sometimes been observed following cessation of chlorine addition, where filter effluent Mn concentration exceeds the influent Mn concentration. In this paper it is hypothesized that Mn-reducing bacteria present in a biofilm on the filter media may be a factor in this Mn-release phenomenon. The primary objective of this research was to assess the role of Mn-reducing microorganisms in the release of soluble Mn from MnO_x(s)-coated filter media following interruption of pre-filtration chlorination. Bench-scale filter column studies were inoculated with Shewanella oneidensis MR-1 to investigate the impacts of a known Mn-reducing bacterium on release of soluble Mn from MnO_x(s) coatings. In situ vial assays were developed to gain insight into the impacts of MnO_x(s) age on bioavailability to Mn-reducing microorganisms and a quantitative polymerase chain reaction (qPCR) method was developed to quantify gene copies of the mtrB gene, which is involved in Mn-reduction. Results demonstrated that microbially-mediated Mn release was possible above a threshold equivalent of 2 × 10² S. oneidensis MR-1 CFU per gram of MnO_x(s) coated media and that those organisms contributed to Mn desorption and release. Further, detectable mtrB gene copies were associated with observed Mn desorption. Lastly, MnO_x(s) age appeared to play a role in Mn reduction and subsequent release, where MnO_x(s) solids of greater age indicated lower bioavailability. These findings can help inform means of preventing soluble Mn release from drinking water treatment plant filters.

SUBMITTER: Swain LE

PROVIDER: S-EPMC6549940 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundRadiotherapy is a commonly used tool in clinical practice to treat solid tumors. However, due to the unique microenvironment inside the tumor, such as high levels of GSH, overexpressed H2O2 and hypoxia, these factors can seriously affect the effectiveness of radiotherapy.ResultsTherefore, to further improve the efficiency of radiotherapy, a core-shell nanocomposite CeO2-MnO2 is designed as a novel radiosensitizer that can modulate the tumor microenvironment (TME) and thus improve the efficacy of radiation therapy. CeO2-MnO2 can act as a radiosensitizer to enhance X-ray absorption at the tumor site while triggering the response behavior associated with the tumor microenvironment. According to in vivo and in vitro experiments, the nanoparticles aggravate the killing effect on tumor cells by generating large amounts of ROS and disrupting the redox balance. In this process, the outer layer of MnO2 reacts with GSH and H2O2 in the tumor microenvironment to generate ROS and release oxygen, thus alleviating the hypoxic condition in the tumor area. Meanwhile, the manganese ions produced by degradation can enhance T1-weighted magnetic resonance imaging (MRI). In addition, CeO2-MnO2, due to its high atomic number oxide CeO2, releases a large number of electrons under the effect of radiotherapy, which further reacts with intracellular molecules to produce reactive oxygen species and enhances the killing effect on tumor cells, thus having the effect of radiotherapy sensitization. In conclusion, the nanomaterial CeO2-MnO2, as a novel radiosensitizer, greatly improves the efficiency of cancer radiation therapy by improving the lack of oxygen in tumor and responding to the tumor microenvironment, providing an effective strategy for the construction of nanosystem with radiosensitizing function.ConclusionIn conclusion, the nanomaterial CeO2-MnO2, as a novel radiosensitizer, greatly improves the efficiency of cancer radiation therapy by improving the lack of oxygen in tumor and responding to the tumor microenvironment, providing an effective strategy for the construction of nanosystems with radiosensitizing function.

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Interference of manganese removal by biologically-mediated reductive release of manganese from MnO_x(s) coated filtration media.

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Interference of manganese removal by biologically-mediated reductive release of manganese from MnOx(s) coated filtration media.

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OmicsDI is part of the ELIXIR infrastructure

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Interference of manganese removal by biologically-mediated reductive release of manganese from MnO_x(s) coated filtration media.