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Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sb(III) oxidation by microorganisms plays a key role in the geochemical cycling of antimony and is effective for bioremediation. A previously discovered novel Sb(III)-oxidizing bacteria, Phytobacter sp. X4, was used to elucidate the response patterns of extracellular polypeptides (EPS), antioxidant system, electron transfer and functional genes to Sb(III) under anaerobic conditions. The toxicity of Sb(III) was mitigated by increasing Sb(III) oxidation capacity, and the EPS regulated the content of each component by sensing the concentration of Sb(III). High Sb(III) concentrations induced significant secretion of proteins and polysaccharides of EPS, and polysaccharides were more important. Functional groups including hydroxyl, carboxyl and amino groups on the cell surface adsorbed Sb(III) to block its entry. Hydroxyl radicals and hydrogen peroxide were involved in anaerobic Sb(III) oxidation, as revealed by changes in the antioxidant system and electron spin resonance (EPR) techniques. qPCR confirmed that proteins concerning nitrate and antimony transfer, antimony resistance and antioxidant system were regulated by Sb(III) concentration, and the synergistic cooperation of multiple proteins conferred high antimony resistance to X4. The adaptive antimony resistance mechanism of Phytobacter sp. X4 under anaerobic conditions was revealed, which also provides a reference value for bioremediation method of antimony contamination in anaerobic environment. [Display omitted] • The production of EPS was not positively correlated with Sb(III) concentration. • The polysaccharides of EPS were more important under high Sb(III) concentration. • •OH and H 2 O 2 were involved in the anaerobic oxidation of Sb(III). • Sb resistance genes and nitrate reduction genes were significantly upregulated. [ABSTRACT FROM AUTHOR]

The role that H2S plays in the global sulfur cycle has been studied extensively in recent years. This paper focuses on the influence of H2S released from gas hydrates on sulfur cycle and establishes a one-dimensional mathematical model to calculate the amount of H2S released from the dissociation of gas hydrates present in multiple layers in the Qiongdongnan Basin China. The results show that the sulfate and methane transition zone that covers an area of about 100 km2in the Qiongdongnan Basin contains 2.3 × 1012 g of pyrite, which requires 4.06 × 1011 mol of H2S for its formation. The H2S released from the dissociation of gas hydrates is 5.4 ×1011 mol, which is about 1.3 times that needed for the formation of pyrite. Therefore, the H2S released from the gas hydrates is an important source of H2S for the formation of pyrite in the sulfate-methane transition zone of Qiongdongnan Basin. According to the flux of H2S and the partial pressure of O2 (PO2) in the atmosphere, the critical value of the balance between the flux of H2S and PO2 turns out to be 0.13 mol kg−1∙bar−1. Furthermore, considering the effect of global sea-level changes, three risk modes are identified to categorize the amount of H2S released from the dissociation of gas hydrate into the atmosphere. We classify the periods from 5–12 Ma BP, 25–29 Ma BP, 47–52 Ma, and 57–61 Ma BP into the high-risk mode. Furthermore, the results show that a part of the H2S released from the gas hydrate dissociation is oxidized by the Fe (III) oxide metal, with much of the metal ions being released into the pore water. Another part of the H2S is re-oxidized by the O2 in the ocean, with much of SO42- released into the seawater. Therefore, the process also provides metal ions and SO42- to pore water or seawater when the H2S released from gas hydrate diffuses from the bottom. This paper provides new insights into the source of H2S in the ocean and shows that the H2S contained in gas hydrates plays an important role in the global sulfur cycle.

This article presents the first experimental data on the ability of microbial communities from sediments of the Gorevoy Utes natural oil seep to degrade petroleum hydrocarbons under anaerobic conditions. Like in marine ecosystems associated with oil discharge, available electron acceptors, in particular sulfate ions, affect the composition of the microbial community and the degree of hydrocarbon conversion. The cultivation of the surface sediments under sulfate-reducing conditions led to the formation of a more diverse bacterial community and greater loss of n-alkanes (28%) in comparison to methanogenic conditions (6%). Microbial communities of both surface and deep sediments are more oriented to degrade polycyclic aromatic hydrocarbons (PAHs), to which the degree of the PAH conversion testifies (up to 46%) irrespective of the present electron acceptors. Microorganisms with the uncultured closest homologues from thermal habitats, sediments of mud volcanoes, and environments contaminated with hydrocarbons mainly represented microbial communities of enrichment cultures. The members of the phyla Firmicutes, Chloroflexi, and Caldiserica (OP5), as well as the class Deltaproteobacteria and Methanomicrobia, were mostly found in enrichment cultures. The influence of gas-saturated fluids may be responsible for the presence in the bacterial 16S rRNA gene libraries of the sequences of "rare taxa": Planctomycetes, Ca. Atribacteria (OP9), Ca. Armatimonadetes (OP10), Ca. Latescibacteria (WS3), Ca. division (AC1), Ca. division (OP11), and Ca. Parcubacteria (OD1), which can be involved in hydrocarbon oxidation. [ABSTRACT FROM AUTHOR]

Iron mineral transformations occurring in hydrocarbon‐contaminated sites are linked to the biodegradation of the hydrocarbons. At a hydrocarbon‐contaminated site near Bemidji, Minnesota, USA, measurements of magnetic susceptibility (MS) are useful for monitoring the natural attenuation of hydrocarbons related to iron cycling. However, a transient MS, previously observed at the site, remains poorly understood and the iron mineral phases acting as reactants and products associated with this MS perturbation remain largely unknown. To address these unknowns, we acquired mineral magnetism measurements, including hysteresis loops, backfield curves, and isothermal remanent magnetizations on sediment core samples retrieved from the site and magnetite‐filled mineral packets installed within the aquifer. Our data show that the core samples and magnetite packs display decreasing magnetization with time and that this loss in magnetization is accompanied by increasing bulk coercivity consistent with decreased average grain size and/or partial oxidation. Low‐temperature magnetometry on all samples displayed behavior consistent with magnetite, but samples within the plume also show evidence of maghemitization. This interpretation is supported by the occurrence of shrinkage cracks on the surface of the grains imaged via scanning electron microscopy. Magnetite transformation to maghemite typically occurs under oxic conditions, here, we propose that maghemitization occurs within the anoxic portions of the plume via microbially mediated anaerobic oxidation. Mineral dissolution also occurs within the plume. Microorganisms capable of such anaerobic oxidation have been identified within other areas at the Bemidji site, but additional microbiological studies are needed to link specific anaerobic iron oxidizers with this loss of magnetization. Plain Language Summary: Iron is the fourth most abundant element in the Earth and can be cycled by microorganisms from one form to another often accompanied by the precipitation of different iron mineral phases. Some of these minerals have magnetic properties resulting in the magnetization of their host rocks. Some studies have documented that the magnetic minerals can be cycled by microorganisms resulting in the increase or loss of the magnetization. The mechanism by which this happens is not well understood. In this study, we conducted an experiment at a hydrocarbon‐contaminated site where iron cycling is occurring to better understand the cause of this loss of magnetization and the accompanying mineral changes associated with this process. Our results show the loss of magnetization is caused by the oxidation of magnetite (a highly magnetic mineral) to maghemite (a less magnetic mineral). This oxidation occurs under oxygen‐limiting conditions caused by microorganisms. However, the oxidation process does not account for all the loss in magnetization, leaving us to suggest dissolution may also be contributing to the loss of magnetization. Our results support that microorganisms may have the potential to mediate changes in the magnetic properties of Earth materials. Key Points: Fluctuations in magnetization may occur due to microbially induced iron mineral transformation in hydrocarbon‐contaminated aquifersLoss of magnetization is due to maghemitization (oxidation) and dissolution of magnetite grainsWithin the anoxic portions of the hydrocarbon plume, maghemitization occurs through anaerobic oxidation induced by microorganisms [ABSTRACT FROM AUTHOR]

[Display omitted] • Dissimilatory iron reduction could mediate efficient anaerobic DCF biodegradation. • DCF biodegradation was facilitated by anaerobic oxidation not reduction. • Aniline hydroxylation and C-N bond break was main biodegradation pathway of DCF. • Genes related to iron reduction was highly expressed during DCF biodegradation. Diclofenac (DCF) is frequently detected in the environments; however, the mechanisms for its anaerobic biodegradation coupled with dissimilatory iron reduction (DIR) are still unclear, particularly the key microbial community and function gene involved in this bioprocess have been rarely identified. The present study firstly demonstrated the microbial-mediated anaerobic oxidation of DCF coupled with DIR. 82.6 ± 2.0 % of DCF (10.0 mg/L) was eliminated with a maximum rate constant (k) of 0.22 day−1 during 90 days' incubation. The amorphous Fe(III) minerals and neutral pH (pH = 7.0) were critical to induce higher dissimilatory iron reducing bacteria (DIRB) availability for the anaerobic DCF biotransformation. DCF could undergo favorable oxidation through transferring electron between DCF and Fe(III), while the hydroxylation of anilines and biotic cleavage of the C-N bond mainly contributed to the transformation. Paraclostridium, Ruminococcaceae_UCG-009 , Prevotella_7 and Anaerofilu would be the main functional microorganisms, synergistically facilitating the DCF degradation. The kyoto encyclopedia of genes and genomes (KEGG) predictive functional profiling analysis showed that the effective improvement (16.94 %∼98.83 %) in the abundance of iron reduction-related genes was induced during the anaerobic bioprocess, thus potentially promoting the biotransformation of DCF. This study would provid a novel insight into the mechanism underlying the anaerobic biotransformation of DCF. [ABSTRACT FROM AUTHOR]

Repeat observations over the Kochi and Mangalore shelves of the southeastern Arabian Sea (SEAS) during April to December 2012 revealed substantial accumulation of methane (CH4) in the nearshore waters (48.6 ± 34.4 nM) compared to the outer shelf (2.9 ± 0.7 nM). Sediment methanogenesis and estuarine discharge appear to be the major sources of CH4 in the nearshore regions during non-upwelling period. But under oxygen deficient conditions that prevail during the upwelling period, extremely low concentrations of CH4 in the nearshore anoxic region of Mangalore (14 ± 2 nM) compared to similar region of hypoxic Kochi shelf (35.5 ± 15.4 nM) have been observed. We propose that this is mainly due to its greater loss through anaerobic oxidation and in part by the reduced sedimentary inputs by weak bioturbation over Mangalore relative to Kochi. On an annual basis, SEAS is found to be a net source of CH4 to the atmosphere with its efflux ranging from 0.03 to 170 μmol m–2 d–1 (21.9 ± 36.7 μmol m–2 d–1). Following a zonal extrapolation approach, the estimated CH4 efflux from the SEAS (7–14°N; 3.2 Gg y–1) accounts for up to ∼16% of the total CH4 emission from the Arabian Sea.

Abstract The major processes that determine the distribution of methane (CH 4) in anoxic marine sediments are methanogenesis and the anaerobic oxidation of methane (AOM), with organoclastic sulfate reduction exerting an important secondary control. However, the factors leading to the distribution of stable carbon isotopes (δ13C) of CH 4 are currently poorly understood, in particular the commonly-observed minimum in δ13C-CH 4 at the sulfate-methane transition (SMT) where AOM rates reach maximum values. Conventional isotope systematics predict 13C-enrichment of CH 4 in the SMT due to preferential 12CH 4 consumption by AOM. Two hypotheses put forward to explain this discrepancy are the addition of 12C-enriched CH 4 to porewaters by methanogenesis in close proximity to AOM, and enzymatically-mediated carbon isotope equilibrium between forward and backward AOM at low concentrations of sulfate. To examine this in more detail, field data including δ13C of CH 4 and dissolved inorganic carbon (DIC) from the continental margin offshore southwestern Taiwan were simulated with a reaction-transport model. Model simulations showed that the minima in δ13C-CH 4 and δ13C-DIC in the SMT could only be simulated with carbon isotope equilibrium during AOM. The potential for carbon cycling between methanogenesis and AOM in and just below the SMT was insignificant due to very low rates of methanogenesis. Backward AOM also gives rise to a pronounced kink in the δ13C-DIC profile several meters below the SMT that has been observed in previous studies. We suggest that this kink marks the true base of the SMT where forward and backward AOM are operating at very low rates, possibly sustained by cryptic sulfur cycling or barite dissolution. [ABSTRACT FROM AUTHOR]

Abstract Stable isotope compositions of methane (δ13C and δD) and of short-chain alkanes are commonly used to trace the origin and fate of carbon in the continental crust. In continental sedimentary systems, methane is typically produced through thermogenic cracking of organic matter and/or through microbial methanogenesis. However, secondary processes such as mixing, migration or biodegradation can alter the original isotopic and composition of the gas, making the identification and the quantification of primary sources challenging. The recently resolved methane 'clumped' isotopologues Δ13CH 3 D and Δ12CH 2 D 2 are unique indicators of whether methane is at thermodynamic isotopic equilibrium or not, thereby providing insights into formation temperatures and/or into kinetic processes controlling methane generation processes, including microbial methanogenesis. In this study, we report the first systematic use of methane Δ13CH 3 D and Δ12CH 2 D 2 in the context of continental sedimentary basins. We investigated sedimentary formations from the Southwest Ontario and Michigan Basins, where the presence of both microbial and thermogenic methane was previously proposed. Methane from the Silurian strata coexist with highly saline brines, and clumped isotopologues exhibit large offsets from thermodynamic equilibrium, with Δ12CH 2 D 2 values as low as −23‰. Together with conventional δ13C and δD values, the variability in Δ13CH 3 D and Δ12CH 2 D 2 to first order reflects a mixing relationship between near-equilibrated thermogenic methane similar to gases from deeper Cambrian and Middle Ordovician units, and a source characterized by a substantial departure from equilibrium that could be associated with microbial methanogenesis. In contrast, methane from the Devonian-age Antrim Shale, associated with less saline porewaters, reveals Δ13CH 3 D and Δ12CH 2 D 2 values that are approaching low temperature thermodynamic equilibrium. While microbial methanogenesis remains an important contributor to the methane budget in the Antrim Shale, it is suggested that Anaerobic Oxidation of Methane (AOM) could contribute to reprocessing methane isotopologues, yielding Δ13CH 3 D and Δ12CH 2 D 2 signatures approaching thermodynamic equilibrium. [ABSTRACT FROM AUTHOR]

Copyright of Geominas is the property of FUNDA-GEOMINAS. (Fundacion de Egresados d Amigos de la Escuela de Ingenieria Geologica y de Minas) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The deep ocean and its sediments are a continuous source of non-methane short-chain alkanes (SCAs) including ethane, propane, and butane. Their high global warming potential, and contribution to local carbon and sulfur budgets has drawn significant scientific attention. Importantly, microbes can use gaseous alkanes and oxidize them to CO2, thus acting as effective biofilters. A relative decrease of these gases with a concomitant 13C enrichment of propane and n-butane in interstitial waters vs. the source suggests microbial anaerobic oxidation. The reported uncoupling of sulfate-reduction (SR) from anaerobic methane oxidation supports their microbial consumption. To date, strain BuS5 isolated from the sediments of Guaymas Basin, Gulf of California, is the only pure culture that can anaerobically degrade propane and n-butane. This organism belongs to a metabolically diverse cluster within the Deltaproteobacteria called Desulfosarcina/Desulfococcus. Other phylotypes involved in gaseous alkane degradation were identified based on stable-isotope labeling and fluorescence in-situ hybridization. A novel syntrophic association of the archaeal genus, Candidatus Syntrophoarchaeum, and a thermophilic SR bacterium, HotSeep-1 was recently discovered from the Guaymas basin, Gulf of California that can anaerobically oxidize n-butane. Strikingly, metagenomic data and the draft genomes of ca. Syntrophoarchaeum suggest that this organism uses a novel mechanism for n-butane oxidation, distinct from the well-established fumarate addition mechanism. These recent findings indicate that a lot remains to be understood about our understanding of anaerobic SCA degradation. This mini-review summarizes our current understanding of microbial anaerobic SCA degradation, and provides an outlook for future research.

The deep ocean and its sediments are a continuous source of non-methane short-chain alkanes (SCAs) including ethane, propane, and butane. Their high global warming potential, and contribution to local carbon and sulfur budgets has drawn significant scientific attention. Importantly, microbes can use gaseous alkanes and oxidize them to CO2, thus acting as effective biofilters. A relative decrease of these gases with a concomitant 13C enrichment of propane and n-butane in interstitial waters vs. the source suggests microbial anaerobic oxidation. The reported uncoupling of sulfate-reduction (SR) from anaerobic methane oxidation supports their microbial consumption. To date, strain BuS5 isolated from the sediments of Guaymas Basin, Gulf of California, is the only pure culture that can anaerobically degrade propane and n-butane. This organism belongs to a metabolically diverse cluster within the Deltaproteobacteria called Desulfosarcina/Desulfococcus. Other phylotypes involved in gaseous alkane degradation were identified based on stable-isotope labeling and fluorescence in-situ hybridization. A novel syntrophic association of the archaeal genus, Candidatus Syntrophoarchaeum, and a thermophilic SR bacterium, HotSeep-1 was recently discovered fromthe Guaymas basin, Gulf of California that can anaerobically oxidize n-butane. Strikingly, metagenomic data and the draft genomes of ca. Syntrophoarchaeum suggest that this organism uses a novel mechanism for n-butane oxidation, distinct from the well-established fumarate addition mechanism. These recent findings indicate that a lot remains to be understood about our understanding of anaerobic SCA degradation. This mini-review summarizes our current understanding of microbial anaerobic SCA degradation, and provides an outlook for future research. [ABSTRACT FROM AUTHOR]

Offshore western Svalbard plumes of gas bubbles rise from the seafloor at the landward limit of the gas hydrate stability zone (LLGHSZ; ∼400 m water depth). It is hypothesized that this methane may, in part, come from dissociation of gas hydrate in the underlying sediments in response to recent warming of ocean bottom waters. To evaluate the potential role of gas hydrate in the supply of methane to the shallow subsurface sediments, and the role of anaerobic oxidation in regulating methane fluxes across the sediment–seawater interface, we have characterised the chemical and isotopic compositions of the gases and sediment pore waters. The molecular and isotopic signatures of gas in the bubble plumes (C 1 /C 2+ = 1 × 10 4 ; δ 13 C-CH 4 = −55 to −51‰; δD-CH 4 = −187 to −184‰) are similar to gas hydrate recovered from within sediments ∼30 km away from the LLGHSZ. Modelling of pore water sulphate profiles indicates that subsurface methane fluxes are largely at steady state in the vicinity of the LLGHSZ, providing no evidence for any recent change in methane supply due to gas hydrate dissociation. However, at greater water depths, within the GHSZ, there is some evidence that the supply of methane to the shallow sediments has recently increased, which is consistent with downslope retreat of the GHSZ due to bottom water warming although other explanations are possible. We estimate that the upward diffusive methane flux into shallow subsurface sediments close to the LLGHSZ is 30,550 mmol m −2 yr −1 , but it is <20 mmol m −2 yr −1 in sediments further away from the seafloor bubble plumes. While anaerobic oxidation within the sediments prevents significant transport of dissolved methane into ocean bottom waters this amounts to less than 10% of the total methane flux (dissolved + gas) into the shallow subsurface sediments, most of which escapes AOM as it is transported in the gas phase. [ABSTRACT FROM AUTHOR]

Denitrification coupled to anaerobic methane oxidation is a recently discovered process performed by bacteria affiliated to the NC10 phylum. These microorganisms could play important roles in the energy-efficient way of anaerobic wastewater treatment where residual dissolved methane might be removed at the expense of nitrate or nitrite. The difficulty to enrich these microorganisms due to a slow growth rate, especially at low temperatures, limited its application in engineering field. In this study, an NC10 bacteria community was enriched from Taihu sediments by a membrane biofilm bioreactor at ambient temperature of 10-25 °C. After 13 months enrichment, the maximum denitrification rate of the enriched culture reached 0.54 mM day for nitrate and 1.06 mM day for nitrite. Anaerobic methane oxidation coupled denitrification was estimated from the C-labeled CO (CO) production during batch incubations with CH. Furthermore, analysis of 16S rRNA genes clone library confirmed the presence of NC10 phylum bacteria and fluorescence in situ hybridization showed that NC10 bacteria dominated the reactor. All of the results indicated the NC10 bacteria community was competitive in terms of treating nitrate-contaminated water or wastewater under natural conditions. [ABSTRACT FROM AUTHOR]

Although the biochemical pathways for the anaerobic degradation of many of the hydrocarbon constituents in petroleum reservoirs have been elucidated, the mechanisms for anaerobic activation of benzene, a very stable molecule, are not known. Previous studies have demonstrated that Geobacter metallireducens can anaerobically oxidize benzene to carbon dioxide with Fe(III) as the sole electron acceptor and that phenol is an intermediate in benzene oxidation. In an attempt to identify enzymes that might be involved in the conversion of benzene to phenol, whole-genome gene transcript abundance was compared in cells metabolizing benzene and cells metabolizing phenol. Eleven genes had significantly higher transcript abundance in benzene-metabolizing cells. Five of these genes had annotations suggesting that they did not encode proteins that could be involved in benzene metabolism and were not further studied. Strains were constructed in which one of the remaining six genes was deleted. The strain in which the monocistronic gene Gmet 0232 was deleted metabolized phenol, but not benzene. Transcript abundance of the adjacent monocistronic gene, Gmet 0231, predicted to encode a zinc-containing oxidoreductase, was elevated in cells metabolizing benzene, although not at a statistically significant level. However, deleting Gmet 0231 also yielded a strain that could metabolize phenol, but not benzene. Although homologs of Gmet 0231 and Gmet 0232 are found in microorganisms not known to anaerobically metabolize benzene, the adjacent localization of these genes is unique to G. metallireducens. The discovery of genes that are specifically required for the metabolism of benzene, but not phenol in G. metallireducens is an important step in potentially identifying the mechanisms for anaerobic benzene activation.

Anaerobic Fe(II) Oxidizing Denitrifiers (AFODN), a type of newly found Fe(II)-oxidizing bacteria, play an important role in iron and nitrogen cycling. In the present study, a novel AFODN strain PXL1 was isolated from anaerobic activated sludge. Phylogenetic analysis of 16S rRNA gene sequence revealed similarity between this strain andCitrobactor freundii. The strain reduced 30% of nitrate and oxidized 85% of Fe(II) over 72 h with an initial Fe(II) concentration of 3.4 mM and nitrate concentration of 9.5 mM. Oxidation of iron was dependent on the reduction of nitrate to nitrite in the absence of other electron donors or acceptors. Nitrate reduction and Fe(II) oxidation followed first-order reaction kinetics. Iron oxides accumulated in the culture were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The strain recovered deposited oxidized Fe in the form of amorphous Fe oxides. [ABSTRACT FROM AUTHOR]

The paper summarizes geochemical data on changes in the organic and inorganic characteristics of naphthoids during their secondary transformation. The hypergenesis phenomena are exemplified with data for oil-and-gas basins of Brazil, Nigeria, and Russia (Sakhalin Island). These are continental-margin basins, in which the original organic matter (OM) is of the mixed coastal-marine and terrigenous origin with a low transformation ratio. The oils are characterized by depleted concentrations of trace elements and nickel metallogeny (Ni/V > 1). By the example of these three basins, the criteria of hypergenetically altered naphthoids have been revealed that make it possible to predict the quality of fluids in such basins upon hypergenetic trans-formation. [ABSTRACT FROM AUTHOR]

Abstract: Aluminized RDX-based explosives were detonated under controlled conditions while varying particle size and atmosphere in an effort to quantify the contribution of aerobic and anaerobic Al reaction to blast and overpressure. Early time reaction of aluminum acts to enhance the primary explosive blast, and this reaction is approximately half aerobic and half anaerobic (i.e. oxidation by detonation products and/or nitridation), suggesting that very rapid early-time mixing occurs in explosive fireballs. Particle size effects are surprisingly negligible over the range of 3–40μm, which implies that conventional scaling laws for aluminum combustion provide less insight than previously assumed. Quasi-static pressures obtained in the time period from 5 to 10microns after detonation suggest that oxidation of aluminum is complete in the presence of 20% oxygen. However, for nitrogen environments, oxidation only proceeds to half its theoretical maximum, except for the smallest (3μm particles) for which oxidation was nearly complete. These results demonstrate that oxidation of aluminum in aluminized explosives is robust in anaerobic environments, and that simulation efforts cannot neglect anaerobic channels, even though aerobic oxidation provides the greatest energy release. [Copyright &y& Elsevier]

Recently discovered microorganisms affiliated to the bacterial phylum NC10, named ' Candidatus Methylomirabilis oxyfera', perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature. [ABSTRACT FROM AUTHOR]

Studies of our laboratory have led to elaboration of the DEAMOX (DEnitrifying AMmonia OXidation) technology intended for removal of nitrogen contaminants from wastewater. The DEAMOX process comprises two anaerobic stages implemented by the same sludge biocatalyst, namely, denitratation (conversion of nitrate to nitrite) and anammox reaction (ANaerobic AMmonium nitrogen OXidation by nitrite). The results of reactivation of biocatalysts after their long-term storage (5 and 16 months) and successful startup of the DEAMOX process in two modifications (S- and O-) are described. An S-DEAMOX process was launched using a sludge biocatalyst with restored anammox activity of 20.1 mg N/g VSS/day; this process provided removal of 78% of nitrogen in reactor over 20 days. The launched O-DEAMOX process with the sludge biocatalyst with anammox activity of 6.1 mg N/g VSS/day provided for 87% removal of the total nitrogen compounds over 30 days. Two different electron donors were used at the stage of nitrate conversion to nitrite, namely, an inorganic donor, sulfide (S-DEAMOX), and an organic one, acetate (O-DEAMOX). [ABSTRACT FROM AUTHOR]

The alteration of physico-chemical properties of sediment organic matter (SOM) incubated under current-harvesting conditions as well as no-current producing conditions over 120 days using sediment microbial fuel cell systems was examined. The SOM was microbially oxidized under anaerobic conditions with an electrode serving as a terminal electron acceptor. It was found that SOM around the electrochemically-active electrodes became more humified, aromatic, and polydispersed, and had a higher average molecular weight, along with its partial degradation and electricity generation compared to that for the original sediment. These changes in SOM properties were analogous to those commonly observed in the early stages of the SOM diagenetic process (i.e. humification). Such a humification-like process was evidently more stimulated when electrical current was produced than no-current condition. These new findings associated with microbially-catalyzed electricity generation may present a potential for the energy-efficient remediation, monitoring, and/or management of the geo-environment. [Copyright &y& Elsevier]

Abstract: Insight into the pathways of biodegradation and external factors controlling their activity is essential in adequate environmental risk assessment of chlorinated aliphatic hydrocarbon pollution. This study focuses on biodegradation of 1,2-dichloroethane (1,2-DCA) in microcosms containing sediment sourced from the European rivers Ebro, Elbe and Danube. Biodegradation was studied under different redox conditions. Reductive dechlorination of 1,2-DCA was observed with Ebro and Danube sediment with chloroethane, or ethene, respectively, as the major dechlorination products. Different reductively dehalogenating micro-organisms (Dehalococcoides spp., Dehalobacter spp., Desulfitobacterium spp. and Sulfurospirillum spp.) were detected by 16S ribosomal RNA gene-targeted PCR and sequence analyses of 16S rRNA gene clone libraries showed that only 2–5 bacterial orders were represented in the microcosms. With Ebro and Danube sediment, indications for anaerobic oxidation of 1,2-DCA were obtained under denitrifying or iron-reducing conditions. No biodegradation of 1,2-DCA was observed in microcosms with Ebro sediment under the different tested redox conditions. This research shows that 1,2-DCA biodegradation capacity was present in different river sediments, but not in the water phase of the river systems and that biodegradation potential with associated microbial communities in river sediments varies with the geochemical properties of the sediments. [Copyright &y& Elsevier]

Abstract: The model simulation study has shown that the anaerobic process of oxidative dehydrogenation of propane under periodic alteration of feeding between propane and air may be realized in adiabatic catalyst beds in a stable continuous cyclic mode in a two-reactor scheme. In the case of an appropriate choice of process parameters (cycle duration and feeding flow rates) the process appears to be autothermal, i.e. it does not require any inlet gas preheating for stable operation. Compared with a similar steady-state adiabatic process, the proposed process is characterized with much lower maximum catalyst temperatures, giving the way to process pure propane without diluting it with inert gases, thus simplifying the downstream procedure of product separation. Predicted propylene yield is competitive with the one for the steady-state adiabatic process, while sufficient technological benefits of the new technology are expected (decrease in energy consumption and minimization of heat-exchange environment, process safety improvement, suppression of coke formation and efficient coke incineration). [Copyright &y& Elsevier]

Abstract: The anaerobic oxidation of isobutane over complex oxide catalysts of the type Cu n V2O x (n =0, 1, 2, 3, and 5) was studied. V2O5, CuV2O6, and Cu2V2O7 showed high oxidizing activity, and Cu3V2O8 and Cu5V2O10 were less active. Over the active catalysts, CO2 was selectively formed only at the beginning of the reaction, and the rate of CO2 formation decreased with reaction time. Isobutene formation became dominant 15–30min after the start of the reaction. The rates of CO2 and isobutene formation were lower over the less active catalysts, Cu3V2O8 and Cu5V2O10. The catalytic activity at 623K decreased in the order V2O5 >CuV2O6, Cu2V2O7 ≫Cu3V2O8, Cu5V2O10. Because CO2 formed at the beginning of the reaction, this system should be applicable for the selective formation of isobutene at appropriate reduction degrees. We concluded that CuV2O6 and Cu2V2O7 should be applicable in a thin-layer reactor, in which isobutane and oxygen are separately supplied to opposite sides of the layer; in such a reactor, the catalyst surface on the isobutane side could be kept at a certain degree of reduction. Using the rate constants for isobutane consumption over Cu2V2O7, we calculated the apparent activation energy for anaerobic oxidation of isobutane to be 87.6kJ/mol, which agrees well with the reported value for a metal oxide catalyst. XPS analysis indicated that not V5+ but Cu2+ was reduced during the reduction of Cu2V2O7 by H2 at 473K. Our results indicate that selective oxidation should be achievable over complex oxides that contain highly redox-active metal ions such as Cu2+ if the reaction is carried out in a thin-layer reactor. [Copyright &y& Elsevier]

Late Pennsylvanian seep limestones (ca. 300 Ma) enclosed in the Ganigobis shales in southern Namibia formed by microbial activity. The process that induced carbonate precipitation was the anaerobic oxidation of methane. The presence of 13C-depleted pentamethylicosane (PMI) (-113‰) and a mixture of crocetane and phytane (-112‰) in concert with similarly 13C-depleted pseudohomologous series of regular isoprenoids reveals that methanotrophic archaea oxidized methane anaerobically at the ancient seep site. Biphytane and a C39 pseudohomologue are other archaeal molecular fossils with δ13C values of -99‰ and -97‰, respectively. The former presence of sulfatereducing bacteria as the syntrophic partners of methanotrophic archaea in the anaerobic oxidation of methane is indicated by isotopically depleted iso- and anteiso-alkanes. These compounds most probably derive from non-isoprenoidal monoethers and diethers, synthates of sulfate-reducing bacteria. These findings show that anaerobic oxidation of methane is at least 300 m.y. old, extending the record of this process for ~140 m.y. As the molecular fossils of archaea and bacteria are preserved in a product of their own metabolic activity (i.e., methane-derived carbonates with δ13C values as low as -51‰), the syngenicity of molecular fossils and enclosing deposits is unambiguous. This reveals that microbially formed rocks can represent excellent archives for studying past biogeochemical processes. [ABSTRACT FROM AUTHOR]

Abstract: Pore water chemical data obtained from a 10.5-m long giant gravity core collected in methane-rich sediments from 647 m water depth in the northern Gulf of Mexico (N 28°04.00′ W 89°43.15′) defines sub-bottom gradients in unprecedented detail. This core penetrated the sulfate-methane interface (SMI) at ∼300 cm below the seafloor (cmbsf). At the SMI dissolved inorganic carbon (DIC) concentrations reach a maximum (13.5 mM) and pore water δ 13C DIC (−63.2‰ PDB) and δ 13C methane (−89.5‰ PDB) values are most negative. Below the SMI pore water sulfate is nearly depleted, methane concentrations rise sharply with simultaneous occurrence of a bubble-textured sediment, and fine-grained methane-derived authigenic carbonate nodules and cements are common. The sharp peaks in DIC concentration and isotope values centered at the SMI indicate that DIC is being produced by anaerobic oxidation of methane (AOM) within a narrow zone centered at the SMI. The detailed sulfate and DIC concentration profiles, and DIC δ 13C values have enabled geochemical models to be constructed that explore the rate of DIC formation by AOM and its effect on pore water DIC δ 13C values. Model results closely match measured DIC concentration and δ 13C isotope profiles and indicate that microbiological conversion of methane carbon to DIC is rapid in geologic terms and that AOM is occurring at the present position of the SMI. Isotope values for authigenic carbonate found immediately below the present-day SMI (δ 13C=−60.2±0.7‰ PDB at 440 cmbsf) are consistent with derivation of the carbonate carbon from methane via AOM at the former location of a SMI. These observations and model results suggest that AOM is occurring at rates that would generate the observed profiles and begin the precipitation of methane-derived carbonate occur on time-scales of centuries. Model results also show that the time needed to produce the resulting authigenic cements is an order of magnitude greater than that for AOM to produce the observed DIC profiles. The metabolic rates for DIC production by AOM inferred from modeling the geochemical profiles compare favorably with available rate data obtained from laboratory microbial incubations and radiolabeled tracer experiments. [Copyright &y& Elsevier]