Anaerobic stabilization and landscape utilization of rural sewage sludge from the enhanced membrane coagulation process.

In this study, enhanced membrane coagulation (EMC) sludge was subjected to various alkaline (pH 7.2, 10, and 11), temperature (35 °C and 55 °C), and duration (0.5 h and 1 day) pretreatment conditions before being inoculated into biogas reactors operated for 176 days.

Enhancing H-driven CO biomethanation performance in bidirectional flow tidal bioreactor by reducing liquid film resistance and heterogeneity.

This study presents a bidirectional flow tidal bioreactor designed to enhance H-driven CO biomethanation. The bioreactor alternated biofilms between immersion in nutrient solution and exposure to H/CO, creating alternating dry and wet states. This tidal operation minimized liquid film thickness during dry periods and ensured uniform nutrient distribution during wet periods.

Electrobiocorrosion by microbes without outer-surface cytochromes.

Anaerobic microbial corrosion of iron-containing metals causes extensive economic damage. Some microbes are capable of direct metal-to-microbe electron transfer (electrobiocorrosion), but the prevalence of electrobiocorrosion among diverse methanogens and acetogens is poorly understood because of a lack of tools for their genetic manipulation. Previous studies have suggested that respiration with 316L  stainless steel as the electron donor is indicative of electrobiocorrosion, because, unlike pure Fe, 316L  stainless steel does not abiotically generate H as an intermediary electron carrier.

Lack of physiological evidence for cytochrome filaments functioning as conduits for extracellular electron transfer.

Unlabelled: Extracellular cytochrome filaments are proposed to serve as conduits for long-range extracellular electron transfer. The primary functional physiological evidence has been the reported inhibition of Fe(III) oxide reduction when the gene for the filament-forming cytochrome OmcS is deleted. Here we report that the OmcS-deficient strain from that original report reduces Fe(III) oxide as well as the wild-type, as does a triple mutant in which the genes for the other known filament-forming cytochromes were also deleted.

Integrated CO capture and conversion via H-driven CO biomethanation: Cyclic performance and microbial community response.

This study investigated the use of H-driven CO biomethanation for integrated CO capture and conversion (iCCC). Anaerobic chambers containing NaCO-amended microbial growth medium provided with H were inoculated with anaerobic granular sludge. Microorganisms were enriched that could regenerate carbonate by using the bicarbonate formed from CO absorption to generate methane.

Detrimental impact of the type VI secretion system on direct interspecies electron transfer.

Direct interspecies electron transfer (DIET) is important in anaerobic communities of environmental and practical significance. Other than the need for close physical contact for electrical connections, the interactions of DIET partners are poorly understood. Type VI secretion systems (T6SSs) typically kill competitive microbes.

Methane production by via direct interspecies electron transfer with .

is widely distributed in natural and artificial anoxic environments and plays a major role in global methane emissions. It is one of only two genera that can form methane from acetate dismutation and through participation in direct interspecies electron transfer (DIET) with exoelectrogens. Although is a significant member of many methanogenic communities, little is known about its physiology.

Cytochrome-mediated direct electron uptake from metallic iron by .

Methane-producing microorganisms accelerate the corrosion of iron-containing metals. Previous studies have inferred that some methanogens might directly accept electrons from Fe(0), but when this possibility was more intensively investigated, H was shown to be an intermediary electron carrier between Fe(0) and methanogens. Here, we report that catalyzes direct metal-to-microbe electron transfer to support methane production.

Different outer membrane -type cytochromes are involved in direct interspecies electron transfer to or species.

Direct interspecies electron transfer (DIET) may be most important in methanogenic environments, but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor. To better understand DIET with methanogens, the transcriptome of during DIET-based growth with reducing fumarate was compared with grown in coculture with diverse . The transcriptome of cocultured with was significantly different from those with .

Enhancement effects of dissolved organic matter leached from sewage sludge on microbial reduction and immobilization of Cr(VI) by Geobacter sulfurreducens.

Sewage sludge has a high concentration of dissolved organic matter (DOM) which contains compounds that can serve as electron donors or shuttles for metal reduction by dissimilatory metal reducing bacteria (DMRB). In this study, Cr(VI) removal by G. sulfurreducens, a common DMRB present in anaerobic soils, was examined in the presence or absence of sludge DOM.

Efficient nitrogen removal from leachate by coupling Anammox and sulfur-siderite-driven denitrification.

High concentrations of nitrate can be generated during anaerobic ammonium oxidation (Anammox) wastewater treatment processes. Addition of sulfur to Anammox reactors stimulates the growth of sulfur-driven denitrifying (SADN) bacteria that can reduce nitrate to nitrogen gas. However, protons released during the SADN process lower the pH of the system and inhibit Anammox activity.

Extracellular Electron Exchange Capabilities of and .

Microbial extracellular electron transfer plays an important role in diverse biogeochemical cycles, metal corrosion, bioelectrochemical technologies, and anaerobic digestion. Evaluation of electron uptake from pure Fe(0) and stainless steel indicated that, in contrast to previous speculation in the literature, and are not able to directly extract electrons from solid-phase electron-donating surfaces. grew with Fe(III) as the electron acceptor, but did not.

Cytochrome OmcS Is Not Essential for Extracellular Electron Transport via Conductive Pili in Geobacter sulfurreducens Strain KN400.

The multi-heme -type cytochrome OmcS is one of the central components used for extracellular electron transport in the Geobacter sulfurreducens strain DL-1, but its role in other microbes, including other strains of G. sulfurreducens, is currently a matter of debate. Therefore, we investigated the function of OmcS in the G.

Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer.

Direct interspecies electron transfer (DIET) between bacteria and methanogenic archaea appears to be an important syntrophy in both natural and engineered methanogenic environments. However, the electrical connections on the outer surface of methanogens and the subsequent processing of electrons for carbon dioxide reduction to methane are poorly understood. Here, we report that the genetically tractable methanogen Methanosarcina acetivorans can grow via DIET in coculture with Geobacter metallireducens serving as the electron-donating partner.

Electromicrobiology: the ecophysiology of phylogenetically diverse electroactive microorganisms.

Electroactive microorganisms markedly affect many environments in which they establish outer-surface electrical contacts with other cells and minerals or reduce soluble extracellular redox-active molecules such as flavins and humic substances. A growing body of research emphasizes their broad phylogenetic diversity and shows that these microorganisms have key roles in multiple biogeochemical cycles, as well as the microbiome of the gut, anaerobic waste digesters and metal corrosion. Diverse bacteria and archaea have independently evolved cytochrome-based strategies for electron exchange between the outer cell surface and the cell interior, but cytochrome-free mechanisms are also prevalent.

Identification of optimal parameters for treatment of high-strength ammonium leachate by mixed communities of heterotrophic nitrifying/aerobic denitrifying bacteria.

Heterotrophic nitrifying and aerobic denitrifying bacteria (HNADB) are important for partial nitrification treatment of high strength ammonium leachate. However, conditions for their optimal performance in mixed reactor systems have yet to be determined. In this study, optimal parameters were identified and included free ammonia (FA) concentrations below 40 mg/L, a dissolved oxygen concentration of 1.

Stainless steel corrosion via direct iron-to-microbe electron transfer by Geobacter species.

Microbial corrosion of iron-based materials is a substantial economic problem. A mechanistic understanding is required to develop mitigation strategies, but previous mechanistic studies have been limited to investigations with relatively pure Fe(0), which is not a common structural material. We report here that the mechanism for microbial corrosion of stainless steel, the metal of choice for many actual applications, can be significantly different from that for Fe(0).

Correlation of Key Physiological Properties of Isolates with Environment of Origin.

It is known that the physiology of species can differ significantly, but the ecological impact of these differences is unclear. We recovered two strains of from two different ecosystems with a similar enrichment and isolation method. Both strains had the same ability to metabolize organic substrates and participate in direct interspecies electron transfer but also had major physiological differences.

Enhanced recovery of nitrous oxide from incineration leachate in a microbial electrolysis cell inoculated with a nosZ-deficient strain of Pseudomonas aeruginosa.

High concentrations of nitrous oxide were recovered from partial nitrification treated leachate in a microbial electrolysis cell (MEC) inoculated with a nosZ-deficient strain of Pseudomonas aeruginosa. NO conversion efficiencies > 90% were achieved when a potential of 0.8 V was applied to the MEC.

Development of a whole-cell biosensor based on an ArsR-P regulatory circuit from .

In this study, an () whole-cell biosensor for the specific detection of bioavailable arsenic was developed by placing a green fluorescent protein (GFP) reporter gene under the control of the ArsR1 (GSU2952) regulatory circuit from . cells only emitted green fluorescence in the presence of arsenite and were more sensitive to arsenite when they were grown in M9 supplemented medium compared to LB medium. Under optimal test conditions, the promoter had a detection limit of 0.

High efficiency in-situ biogas upgrading in a bioelectrochemical system with low energy input.

Biogas produced from anaerobic digestion usually contains 30%-50% CO much of which must be removed, before utilization. Bioelectrochemical biogas upgrading approaches show promise, however, they have not yet been optimized for practical applications. In this study, a bioelectrochemical system with low energy input (applied cathode potential of -0.

Iron Transformation and Its Role in Phosphorus Immobilization in a UCT-MBR with Vivianite Formation Enhancement.

The formation of vivianite (Fe(PO)·8HO) in iron (Fe)-dosed wastewater treatment facilities has the potential to develop into an economically feasible method of phosphorus (P) recovery. In this work, a long-term steady Fe-dosed University of Cape Town process-membrane bioreactor (UCT-MBR) system was investigated to evaluate the role of Fe transformations in immobilizing P via vivianite crystallization. The highest fraction of Fe, to total Fe (Fe), was observed in the anaerobic chamber, revealing that a redox condition suitable for Fe reduction was established by improving operational and configurational conditions.

Protein Nanowires: the Electrification of the Microbial World and Maybe Our Own.

Electrically conductive protein nanowires appear to be widespread in the microbial world and are a revolutionary "green" material for the fabrication of electronic devices. Electrically conductive pili (e-pili) assembled from type IV pilin monomers have independently evolved multiple times in microbial history as have electrically conductive archaella (e-archaella) assembled from homologous archaellin monomers. A role for e-pili in long-range (micrometer) extracellular electron transport has been demonstrated in some microbes.