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Microbial Sulfate-Reducing Activities in Anoxic Sediment from Marine Lake Grevelingen: Screening of Electron Donors and Acceptors
Published in Chiara Cassarini, Anaerobic Oxidation of Methane Coupled to the Reduction of Different Sulfur Compounds as Electron Acceptors in Bioreactors, 2019
The coastal marine sediment from the marine Lake Grevelingen (MLG), the Netherlands, has a special microbial ecology as it harbors both cable bacteria (Hagens et al. 2015; Vasquez-Cardenas et al. 2015; Sulu-Gambari et al. 2016) and anaerobic methanotrophs (ANME) (Bhattarai et al. 2017). A recent study on geochemical data modeling has predicted that SR and methanogenesis might be prominent microbial processes in the MLG sediment, while a large amount of CH4 could be diffused out yielding minimum AOM (Egger et al. 2016). Nevertheless, AOM-SR was observed in the sediment in the presence of anaerobic methane oxidizing communities (Bhattarai et al. 2017). Based on these findings, high rate of SR with commonly used electron donors, such as acetate and ethanol, can be expected, while there could be possible involvement of other sulfur compounds for AOM, besides SO42-, e.g. S0 (Milucka et al. 2012). Therefore, the main objective of this study was to determine the sulfate reducing activities with different electron donors, i.e. ethanol, acetate and lactate in order to compare which one was preferred by the sulfate reducing communities inhabiting the sediment investigated. Further, potential involvement of alternative sulfur compounds (S0and S2O32-) as electron acceptors for AOM-SR activities were investigated and compared with the AOM-SR rate achieved by SO42- as an electron acceptor.
Physiology and Distribution of Anaerobic Oxidation of Methane by Archaeal Methanotrophs
Published in Susma Bhattarai Gautam, Performance Assessment and Enrichment of Anaerobic Methane Oxidising Microbial Communities from Marine Sediments in Bioreactors, 2018
Another mode of e-transfer can occur via highly conductive pili or nanowires (Figure 2.5A), which have been well described in the Fe(III) reducer Geobacter sulfurreducens (Reguera et al., 2005). Recently, a longer nanowire, which facilitates the e-transfer in the range of centimeter scales, has been described in marine environments (Nielsen et al., 2010; Vasquez-Cardenas et al., 2015). A novel cable bacterium putatively belonging to the Desulfobulbaceae and growing as a long filament of around 1 cm length performing e-transport was retrieved from the marine lake Grevelingen (North Sea, The Netherlands) (Vasquez-Cardenas et al., 2015). These cable bacteria are heterotrophs, yet the carbon metabolism has to be defined. Together with other chemolithoautotrophic bacteria, cable bacteria perform electrogenic sulfur oxidation via their long filament (Vasquez-Cardenas et al., 2015). Interestingly, one clade of the cocci shaped DBB is commonly associated with ANME (specifically ANME-3), however long filaments have not yet been visualized in the FISH based studies of ANME sites (Niemann et al., 2006b).
Recent advances in improving the remediation performance of microbial electrochemical systems for contaminated soil and sediments
Published in Critical Reviews in Environmental Science and Technology, 2023
Ruixiang Li, Jinning Wang, Tian Li, Qixing Zhou
In thicker biofilms, cytochrome and multi-heme proteins mediated DET were performed by the first layer of bacteria. The majority of microorganisms far from the electrode surface transfer electrons to the electrode surface via long-distance DET by nanowire (Malvankar et al., 2014). It is generally believed that the nanowires of Geobacter sulfurreducens are mainly type IV pili, but the mechanism of pili-mediated electron transfer is not yet uniformly understood. In addition to the aromatic amino acids of pili, cytochrome (e.g. OmcS) located in the pili have been considered to be key substances for electron transfer (Leang et al., 2010). However, this theory seems to have been overturned by a mutant strain experiment (Liu, Tremblay, et al., 2014). There is no unified view on the mechanism of pili-mediated electron transfer which remains to be further investigated. In addition, cable microorganisms in sediments can achieve centimeter-long microbial electron transfer through the gradients in cytochrome redox potential (Bjerg et al., 2018; Yuan et al., 2021). Cable bacteria can use electron donors and acceptors that are separated by distance, even in nutrient-poor environments (Meysman, 2018). Interestingly, the addition of some conductive materials to the soil/sediments enables the formation of a conductive network in the soil/sediment matrix, thus enabling long-distance DET (Cai et al., 2020). Compared to relying on electron shuttles, DET allows for higher kinetic rates of electron transfer.