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Microbiomes and Metallic Nanoparticles in Remediation of Contaminated Environments
Published in Vivek Kumar, Rhizomicrobiome Dynamics in Bioremediation, 2021
Ana Maria Queijeiro López, Amanda Lys dos Santos Silva, Elane Cristina Lourenço dos Santos, Jean Phellipe Marques do Nascimento
Therefore, the nanoscale size of metal nanoparticles (MtNPs) produced by microorganisms allowed them to have new or better properties than the larger particles from which they originated, with particular physicochemical and biological characteristics according to their size, distribution, morphology, phase, composition, among others. Nanobioremediation was used by Alabresm et al. (2018) to degrade oil spills, and this can be used in contaminated marine and non-marine systems. On the other hand, microbes highly resistant to the toxicity of gold ions were isolated from mines of this metal and could be used efficiently in the synthesis of nanoparticles of the same (AuNPs). In face of its ability to generate bioelectricity and reduce metals, the strain of Shewanella oneidensis MR-1 is broadly used in the recovery of precious metals, bioremediation, and AuNPs fabrication. Huang et al. (2019) reported, for the first time in this strain, the mechanism for the formation of AuNPs through the accumulation of photons based on the intensity and wavelength of light. Srinath et al. (2018) used B. subtilis isolated from Hatti Gold Mine (India) for the synthesis of AuNPs, which were then used as catalysts for the degradation of methylene blue dye, with a view to later use in the decomposition of other dyes toxic to the environment.
Advances in electrochemically active bacteria: Physiology and ecology
Published in Maximilian Lackner, Philipp Stadler, Wilhelm Grabow, Handbook of Online and Near-real-time Methods in Microbiology, 2017
A.C. Marques, L. Santos, J.M. Dantas, A. Gonçalves, S. Casaleiro, R. Martins, C.A. Salgueiro, E. Fortunato
Another metal-reducing organism, that also has been extensively used as a genetically tractable model for EAB, is the Shewanella oneidensis MR-1 bacterium. This bacterium can directly contact and reduce both metal oxides and electrodes, using a set of c-type cytochromes that electronically connect the cell’s cytoplasm with the extracellular electron acceptor. It was proposed that the final step that connects the bacterium periplasm and extracellular electron acceptors in S. oneidensis involves the outer membrane MtrCABOmcA complex (Borole et al. 2011, Paquete et al. 2014). In this heterotrimeric outer membrane complex MtrA, located in the periplasm and associated with the porin MtrB, receives electrons either directly from inner membrane tetraheme cytochrome CymA via a small periplasmic tetraheme cytochrome (STC) and/or via a periplasmic flavocytochrome c3 and facilitates the passage of electrons to MtrC at the microbe-mineral interface. MtrC can then transfer electrons to the terminal acceptor or to cytochrome OmcA, as recently suggested by Paquete and co-workers (Paquete et al. 2014).
Energy harvesting using exoelectrogenic Shewanella oneidensis bacteria
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Young H. Park, Edward Park, Geoffrey Smith
Researches have been conducted to study exoelectrogenic Shewanella oneidensis bacteria that control the redox transformation of heavy metals and other electron acceptors for use in energy conversion (Lies et al. 2005). An important feature of S. oneidensis bacteria is that they produce electrically conductive nanowires that facilitate electron transfer to electron acceptors. Hence, research attempts were made to use S. oneidensis for a mediator-free microbial fuel cell (MFC) that can treat wastewater and produce electricity simultaneously without any synthetic mediators (Kim et al. 2002). The cost of the S. oneidensis based MFC can be reduced and the design simplified compared to MFCs based on bacterial species that are inactive for the transport of electrons and thus need electron transport mediators that shuttle the electrons between microbes and electrodes (Park and Zeikus 2000). In the S. oneidensis based MFC, the electrons are released via catalytic oxidation of organic substrates by S. oneidensis bacteria and transferred to the anode by bacterial nanowires in the anode chamber (Pirbadian et al. 2014; Reguera et al. 2005). The electrons eventually reach the cathode via an external electrical circuit and combine with electron acceptor (oxygen) and the protons that move from the anode chamber to the cathode chamber through a separator; the resulting byproduct is water in the cathode chamber (Bond et al., 2002; Min and Logan 2004). Proton-exchange membranes are widely used as a separator for efficient transport for protons from the anode to the cathode while impeding substrate and oxygen to penetrate. Due to the high cost of these membranes, low cost alternatives such as PVDF-co-HFP (Kumar et al. 2015) and a blend of polybenzimidazole (PBI) and polyvinylpyrrolidone (PVP) (Kumar et al. 2016b) were considered as a separator. Nanomaterial as a nano-filler was also utilized in the blend of a PVDF-co-HFP to increase the efficiency (Kumar et al. 2016a). Shewanella oneidensis is dissimilatory metal-reducing bacteria (DMRB) that can reduce metal compounds. While the anode is engaged in substrate oxidation in the form of wastewater, the cathode can accept electrons produced and catalyze metal oxidation by the DMRB, which can use metals as electron acceptors. Wastewater containing heavy metal such as Co (III) (Huang et al. 2014) and Cr (VI) (Wu et al. 2015) thus can be treated successfully (Wang and Ren 2014) with DMRB. Hence a Shewanella oneidensis based MFC offers potential benefits for environmental sustainability as well as sustainable technology for simultaneous wastewater treatment and electrical power generation (Wu et al. 2018). In this study, we designed a single chamber membraneless bioreactor and harvested energy from the reactor in which electrons were transported from oxidation region to reduction region directly by Shewanella nanowires without an external circuit or a separator.