Cable bacteria (CB) are multicellular, filamentous bacteria within the family of Desulfobulbaceae... more Cable bacteria (CB) are multicellular, filamentous bacteria within the family of Desulfobulbaceae that transfer electrons longitudinally from cell to cell to couple sulfide oxidation and oxygen reduction in surficial aquatic sediments. In the present study, electrochemical reactors that contain natural sediments are introduced as a tool for investigating the growth of CB on electrodes poised at an oxidizing potential. Our experiments utilized sediments from Yaquina Bay, Oregon, USA, and we include new phylogenetic analyses of separated filaments to confirm that CB from this marine location cluster with the genus "Candidatus Electrothrix". These CB may belong to a distinctive lineage, however, because their filaments contain smaller cells and a lower number of longitudinal ridges compared to cables described from other locales. The results of a 135 d bioelectrochemical reactor experiment confirmed that these CB can migrate out of reducing sediments and grow on oxidatively poised electrodes suspended in anaerobic seawater. CB filaments and several other morphologies of Desulfobulbaceae cells were observed by scanning electron microscopy and fluorescence in situ hybridization on electrode surfaces, albeit in low densities and often obscured by mineral precipitation. These findings provide new information to suggest what kinds of conditions will induce CB to perform electron donation to an electrode surface, further informing future experiments to culture CB outside of a sediment matrix.
Journal of Atmospheric and Oceanic Technology, Mar 1, 2016
Most oceanographic instruments on the seafloor have no connections with the surface and therefore... more Most oceanographic instruments on the seafloor have no connections with the surface and therefore have to run on batteries and store data until recovery. To demonstrate a developing technology, sensors and acoustic modems were powered with energy harvested from the seafloor, and data were relayed acoustically in nearreal time to the Monterey Accelerated Research System (MARS) observatory in Monterey Bay, California, and to surface research vessels. MARS is a cabled observatory in deep water (;890 m) at the edge of Monterey Canyon. An acoustic modem was attached to the MARS node and configured to send out commands to, and relay data received from, remote modems. Two benthic microbial fuel cells (BMFCs) positioned approximately 0.5 km away from MARS supplied power to the remote modems and sensors. At their peak performance, these BMFCs produced continuous power densities of ;35 mW m 22 (footprint area). The modems utilized in this study contained an integrated power management platform (PMP) designed to manage and store the electrical energy generated by each BMFC and to record BMFC performance parameters and sensor data on an hourly basis. Temperature and either oxygen or conductivity sensors were chosen because of their common use and environmental relevance. Acoustically transmitted data records show that the BMFCs renewed energy stores and that the oceanographic sensors measured dissolved oxygen, temperature, and conductivity reliably throughout the operational life of each BMFC system (;6 months). These systems remained in place for more than 12 months.
The scope of the present study is to introduce electrochemical reactors as a tool for investigati... more The scope of the present study is to introduce electrochemical reactors as a tool for investigating the growth of novel filamentous cable bacteria and their unique extracellular electron transfer ability. New evidence that cable bacteria are widely distributed in sediments throughout an estuarine system connected to the NE Pacific Ocean is also presented. Cable bacteria found within Yaquina Bay, Oregon, USA, appear to cluster with the genus, Candidatus Electrothrix. Results of a 135-day bioelectrochemical reactor experiment confirm a previous observation that cable 10 bacteria can grow on oxidatively poised electrodes suspended in anaerobic seawater above reducing sediments. However, several diverse morphologies of Desulfobulbaceae filaments, cells, and colonies were observed on the carbon fibers of the suspended electrodes including encrusted chains of cells. These observations provide new information to suggest what conditions will induce cable bacteria to perform electron donation to an electrode surface, further informing future experiments to culture cable bacteria apart from a sediment matrix. 15 1 Introduction Long distance electron transfer (LDET) is a mechanism used by certain microorganisms to generate energy through the transfer of electrons over distances greater than a cell-length. These microorganisms may pass electrons across dissolved redox shuttles, nanofiber-like cell appendages, outer-membrane cytochromes, and/or mineral nanoparticles to connect extracellular electron donors and acceptors (Li et al., 2017; Lovley, 2016). Recently, a novel type of LDET 20 exhibited by filamentous bacteria in the family of Desulfobulbaceae was discovered in the uppermost centimeters of various aquatic, but mainly marine, sediments (Malkin et al., 2014; Pfeffer et al., 2012). These filamentous bacteria, also known as "cable bacteria", electrically connect two spatially separated redox half-reactions and generate electrical current over distances that can extend to centimeters, which is an order of magnitude longer than previously recognized LDET distances (Meysman, 2017). 25 The unique ability of cable bacteria to perform LDET creates a spatial separation of oxygen reduction in oxic surface layers of sediment from sulfide oxidation in subsurface layers (Meysman, 2017). The spatial separation of these two half-reactions also creates localized porewater pH extremes in oxic and sulfidic layers, which induces a series of secondary reactions that stimulate the geochemical cycling of elements such as iron, manganese, calcium, phosphorus,
Distributions of pore water O2, NO-2, NO-3, NH+4, Si(OH)4, PO[3-]4, Mn[2+], F-, and T.A. were det... more Distributions of pore water O2, NO-2, NO-3, NH+4, Si(OH)4, PO[3-]4, Mn[2+], F-, and T.A. were determined at 15 stations in the eastern equatorial Atlantic. While overall profile characteristics are consistent with previous models of organic matter diagenesis, profile shapes suggest that a deep reaction layer, rich in organic C, is also present at many sites. While it is unlikely that the oxidation of organic C in this layer has had a major effect on the ocean C cycle, pore water profile shapes are significantly altered. Despite exposure to seawater SO[2-]4 concentrations for > 1000 years, decomposition of the organic matter in the layer appears to be restricted to oxic and suboxic processes. These results suggest major differences in organic carbon decomposition and preservation under oxic/suboxic and anoxic conditions.Present-day benthic fluxes are largest adjacent to the eastern boundary coastal upwelling region and similar in magnitude to values reported for the eastern Pacifi...
Journal of Atmospheric and Oceanic Technology, 2016
Interest in validating the eddy covariance (EC) technique under wave-induced flows led to a serie... more Interest in validating the eddy covariance (EC) technique under wave-induced flows led to a series of experiments in a 104-m-long large wave flume (LWF) using an acoustic Doppler velocimeter (ADV) and two oxygen microelectrodes (tips ~2 mm apart) mounted on a sturdy tripod. Four additional ADVs positioned within the flume provided comparative near-bed velocity measurements during experiments with irregular waves over a sand bed. These measurements revealed that modifications of local turbulence by the tripod frame were insignificant. However, errors in velocity measurements were at times observed for setups where the microelectrode tips protruded into the ADV’s measurement volume. Disparate oxygen microelectrode velocity effects (stirring sensitivities) combined with response time offsets were also identified as problems, adding biases to EC flux derivations. Microelectrode velocity effects were further investigated through modeling designed to mimic the LWF data, and through examin...
The recent global increase of 1% per year in the concentration of atmospheric methane (CH4) is we... more The recent global increase of 1% per year in the concentration of atmospheric methane (CH4) is well documented (Rasmussen and Khalil 1984; Steele et al. 1987; Blake and Rowland 1989). This increase causes concern because CH4 is an important trace gas in the earth’s atmosphere. Greenhouse warming from CH4 is 25% of CO2-induced warming, and together these gases account for 75% of the radiative trapping from atmospheric gases (Rodhe 1990).
Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse... more Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse-grained Middle Atlantic Bight shelf sediments in relation to pools of dissolved and particulate carbon. Algal cells were present 8^11 cm into the sediment, probably due to hydrodynamically induced pore water flushing and sediment mixing. The coarse-grained (s 70 Wm) fraction of the sediment held the major share (61^98%) of benthic bacteria. Bacterial and algal cell abundances, exoenzymatic activity, and [DOC] generally showed higher values in May/July 2001 than in August/December 2000. Carbohydrates and proteins were hydrolyzed at potential rates of 1^12 nmol cm 33 h 31 (L-glucosidase) and 3^70 nmol cm 33 h 31 (aminopeptidase), respectively. Fluorescence in situ hybridization analyses of the benthic microbes assigned 45^56% of DAPI-stained cells to Eubacteria and less than 2% to Eukarya. The prokaryotic community was dominated by planctomycetes and members of the Cytophaga/Flavobacterium cluster. Near the sediment surface, iodonitrotetrazolium violet reducing cells, that are considered actively respiring, amounted to 15^29% of total bacteria. Despite a low organic content (particulate organic carbon 6 0.03%) and relatively low bacterial abundances (6 10 9 cm 33), the Middle Atlantic Bight shelf sediments showed organic matter turnover rates that are comparable to those found in organic-rich finer-grained deposits. Our findings suggest a high biocatalytic filtration activity in these coarse permeable sediments.
Rates of sediment community oxygen consumption determined in situ are compared to fluxes predicte... more Rates of sediment community oxygen consumption determined in situ are compared to fluxes predicted from oxygen microelectrode gradients measured in cores from ∼3,750‐m water depth in the eastern North Pacific. Oxygen concentrations decrease exponentially over > 1.5 cm and suggest that organic matter in the sediments is degraded most rapidly immediately below the sediment‐water interface.Molecular diffusion of oxygen across the interface is modeled as an “internal regime” and can account for nearly all the directly measured in situ flux, 0.20±0.02 µmol cm−2 d−1. This differs from published accounts of nearshore marine environments, where activity of bottom‐dwelling macrofauna or bubble ebullition enhances benthic fluxes of dissolved nutrients or gases 2–4 times. Millimeter depth‐scale profiles of porosity, organic C, carbonate C, and bacterial abundance are reported to provide additional constraints on interface processes, including the relative effects of organic matter degradati...
Cable bacteria (CB) are multicellular, filamentous bacteria within the family of Desulfobulbaceae... more Cable bacteria (CB) are multicellular, filamentous bacteria within the family of Desulfobulbaceae that transfer electrons longitudinally from cell to cell to couple sulfide oxidation and oxygen reduction in surficial aquatic sediments. In the present study, electrochemical reactors that contain natural sediments are introduced as a tool for investigating the growth of CB on electrodes poised at an oxidizing potential. Our experiments utilized sediments from Yaquina Bay, Oregon, USA, and we include new phylogenetic analyses of separated filaments to confirm that CB from this marine location cluster with the genus "Candidatus Electrothrix". These CB may belong to a distinctive lineage, however, because their filaments contain smaller cells and a lower number of longitudinal ridges compared to cables described from other locales. The results of a 135 d bioelectrochemical reactor experiment confirmed that these CB can migrate out of reducing sediments and grow on oxidatively poised electrodes suspended in anaerobic seawater. CB filaments and several other morphologies of Desulfobulbaceae cells were observed by scanning electron microscopy and fluorescence in situ hybridization on electrode surfaces, albeit in low densities and often obscured by mineral precipitation. These findings provide new information to suggest what kinds of conditions will induce CB to perform electron donation to an electrode surface, further informing future experiments to culture CB outside of a sediment matrix.
Journal of Atmospheric and Oceanic Technology, Mar 1, 2016
Most oceanographic instruments on the seafloor have no connections with the surface and therefore... more Most oceanographic instruments on the seafloor have no connections with the surface and therefore have to run on batteries and store data until recovery. To demonstrate a developing technology, sensors and acoustic modems were powered with energy harvested from the seafloor, and data were relayed acoustically in nearreal time to the Monterey Accelerated Research System (MARS) observatory in Monterey Bay, California, and to surface research vessels. MARS is a cabled observatory in deep water (;890 m) at the edge of Monterey Canyon. An acoustic modem was attached to the MARS node and configured to send out commands to, and relay data received from, remote modems. Two benthic microbial fuel cells (BMFCs) positioned approximately 0.5 km away from MARS supplied power to the remote modems and sensors. At their peak performance, these BMFCs produced continuous power densities of ;35 mW m 22 (footprint area). The modems utilized in this study contained an integrated power management platform (PMP) designed to manage and store the electrical energy generated by each BMFC and to record BMFC performance parameters and sensor data on an hourly basis. Temperature and either oxygen or conductivity sensors were chosen because of their common use and environmental relevance. Acoustically transmitted data records show that the BMFCs renewed energy stores and that the oceanographic sensors measured dissolved oxygen, temperature, and conductivity reliably throughout the operational life of each BMFC system (;6 months). These systems remained in place for more than 12 months.
The scope of the present study is to introduce electrochemical reactors as a tool for investigati... more The scope of the present study is to introduce electrochemical reactors as a tool for investigating the growth of novel filamentous cable bacteria and their unique extracellular electron transfer ability. New evidence that cable bacteria are widely distributed in sediments throughout an estuarine system connected to the NE Pacific Ocean is also presented. Cable bacteria found within Yaquina Bay, Oregon, USA, appear to cluster with the genus, Candidatus Electrothrix. Results of a 135-day bioelectrochemical reactor experiment confirm a previous observation that cable 10 bacteria can grow on oxidatively poised electrodes suspended in anaerobic seawater above reducing sediments. However, several diverse morphologies of Desulfobulbaceae filaments, cells, and colonies were observed on the carbon fibers of the suspended electrodes including encrusted chains of cells. These observations provide new information to suggest what conditions will induce cable bacteria to perform electron donation to an electrode surface, further informing future experiments to culture cable bacteria apart from a sediment matrix. 15 1 Introduction Long distance electron transfer (LDET) is a mechanism used by certain microorganisms to generate energy through the transfer of electrons over distances greater than a cell-length. These microorganisms may pass electrons across dissolved redox shuttles, nanofiber-like cell appendages, outer-membrane cytochromes, and/or mineral nanoparticles to connect extracellular electron donors and acceptors (Li et al., 2017; Lovley, 2016). Recently, a novel type of LDET 20 exhibited by filamentous bacteria in the family of Desulfobulbaceae was discovered in the uppermost centimeters of various aquatic, but mainly marine, sediments (Malkin et al., 2014; Pfeffer et al., 2012). These filamentous bacteria, also known as "cable bacteria", electrically connect two spatially separated redox half-reactions and generate electrical current over distances that can extend to centimeters, which is an order of magnitude longer than previously recognized LDET distances (Meysman, 2017). 25 The unique ability of cable bacteria to perform LDET creates a spatial separation of oxygen reduction in oxic surface layers of sediment from sulfide oxidation in subsurface layers (Meysman, 2017). The spatial separation of these two half-reactions also creates localized porewater pH extremes in oxic and sulfidic layers, which induces a series of secondary reactions that stimulate the geochemical cycling of elements such as iron, manganese, calcium, phosphorus,
Distributions of pore water O2, NO-2, NO-3, NH+4, Si(OH)4, PO[3-]4, Mn[2+], F-, and T.A. were det... more Distributions of pore water O2, NO-2, NO-3, NH+4, Si(OH)4, PO[3-]4, Mn[2+], F-, and T.A. were determined at 15 stations in the eastern equatorial Atlantic. While overall profile characteristics are consistent with previous models of organic matter diagenesis, profile shapes suggest that a deep reaction layer, rich in organic C, is also present at many sites. While it is unlikely that the oxidation of organic C in this layer has had a major effect on the ocean C cycle, pore water profile shapes are significantly altered. Despite exposure to seawater SO[2-]4 concentrations for > 1000 years, decomposition of the organic matter in the layer appears to be restricted to oxic and suboxic processes. These results suggest major differences in organic carbon decomposition and preservation under oxic/suboxic and anoxic conditions.Present-day benthic fluxes are largest adjacent to the eastern boundary coastal upwelling region and similar in magnitude to values reported for the eastern Pacifi...
Journal of Atmospheric and Oceanic Technology, 2016
Interest in validating the eddy covariance (EC) technique under wave-induced flows led to a serie... more Interest in validating the eddy covariance (EC) technique under wave-induced flows led to a series of experiments in a 104-m-long large wave flume (LWF) using an acoustic Doppler velocimeter (ADV) and two oxygen microelectrodes (tips ~2 mm apart) mounted on a sturdy tripod. Four additional ADVs positioned within the flume provided comparative near-bed velocity measurements during experiments with irregular waves over a sand bed. These measurements revealed that modifications of local turbulence by the tripod frame were insignificant. However, errors in velocity measurements were at times observed for setups where the microelectrode tips protruded into the ADV’s measurement volume. Disparate oxygen microelectrode velocity effects (stirring sensitivities) combined with response time offsets were also identified as problems, adding biases to EC flux derivations. Microelectrode velocity effects were further investigated through modeling designed to mimic the LWF data, and through examin...
The recent global increase of 1% per year in the concentration of atmospheric methane (CH4) is we... more The recent global increase of 1% per year in the concentration of atmospheric methane (CH4) is well documented (Rasmussen and Khalil 1984; Steele et al. 1987; Blake and Rowland 1989). This increase causes concern because CH4 is an important trace gas in the earth’s atmosphere. Greenhouse warming from CH4 is 25% of CO2-induced warming, and together these gases account for 75% of the radiative trapping from atmospheric gases (Rodhe 1990).
Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse... more Spatiotemporal variation and metabolic activity of the microbial community were studied in coarse-grained Middle Atlantic Bight shelf sediments in relation to pools of dissolved and particulate carbon. Algal cells were present 8^11 cm into the sediment, probably due to hydrodynamically induced pore water flushing and sediment mixing. The coarse-grained (s 70 Wm) fraction of the sediment held the major share (61^98%) of benthic bacteria. Bacterial and algal cell abundances, exoenzymatic activity, and [DOC] generally showed higher values in May/July 2001 than in August/December 2000. Carbohydrates and proteins were hydrolyzed at potential rates of 1^12 nmol cm 33 h 31 (L-glucosidase) and 3^70 nmol cm 33 h 31 (aminopeptidase), respectively. Fluorescence in situ hybridization analyses of the benthic microbes assigned 45^56% of DAPI-stained cells to Eubacteria and less than 2% to Eukarya. The prokaryotic community was dominated by planctomycetes and members of the Cytophaga/Flavobacterium cluster. Near the sediment surface, iodonitrotetrazolium violet reducing cells, that are considered actively respiring, amounted to 15^29% of total bacteria. Despite a low organic content (particulate organic carbon 6 0.03%) and relatively low bacterial abundances (6 10 9 cm 33), the Middle Atlantic Bight shelf sediments showed organic matter turnover rates that are comparable to those found in organic-rich finer-grained deposits. Our findings suggest a high biocatalytic filtration activity in these coarse permeable sediments.
Rates of sediment community oxygen consumption determined in situ are compared to fluxes predicte... more Rates of sediment community oxygen consumption determined in situ are compared to fluxes predicted from oxygen microelectrode gradients measured in cores from ∼3,750‐m water depth in the eastern North Pacific. Oxygen concentrations decrease exponentially over > 1.5 cm and suggest that organic matter in the sediments is degraded most rapidly immediately below the sediment‐water interface.Molecular diffusion of oxygen across the interface is modeled as an “internal regime” and can account for nearly all the directly measured in situ flux, 0.20±0.02 µmol cm−2 d−1. This differs from published accounts of nearshore marine environments, where activity of bottom‐dwelling macrofauna or bubble ebullition enhances benthic fluxes of dissolved nutrients or gases 2–4 times. Millimeter depth‐scale profiles of porosity, organic C, carbonate C, and bacterial abundance are reported to provide additional constraints on interface processes, including the relative effects of organic matter degradati...
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Papers by Clare Reimers