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The phenomenon of methane oxidation linked to perchlorate reduction has been reported in multiple studies; yet, the underlying microbial mechanisms remain unclear. Here, we enriched suspended cultures by performing methane-driven perchlorate reduction under oxygen-limiting conditions in a membrane bioreactor (MBR). Batch test results proved that perchlorate reduction was coupled to methane oxidation, in which acetate was predicted as the potential intermediate and oxygen played an essential role in activating methane. By combining DNA-based stable isotope probing incubation and high-throughput sequencing analyses of 16S rRNA gene and functional genes (pmoA, pcrA, and narG), we found that synergistic interactions between aerobic methanotrophs (Methylococcus and Methylocystis) and perchlorate-reducing bacteria (PRB; Denitratisoma and Dechloromonas) played active roles in mediating methane-driven perchlorate reduction. This partnership was further demonstrated by coculture experiments in which the aerobic methanotroph could produce acetate to support PRB to complete perchlorate reduction. Our findings advance the understanding of the methane-driven perchlorate reduction process and have implications for similar microbial consortia linking methane and chlorine biogeochemical cycles in natural environments.
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Biogas produced from anaerobic digestion usually contains impurities, particularly with a high content of CO2 (15-60%), thus decreasing its caloric value and limiting its application as an energy source. H2-driven biogas upgrading using homoacetogens is a promising approach for upgrading biogas to biomethane and converting CO2 to acetate simultaneously. Herein, we developed a novel membrane biofilm reactor (MBfR) with H2 and biogas separately supplied via bubbleless hollow fiber membranes. The gas-permeable hollow fibers of the MBfR enabled high H2 and CO2 utilization efficiencies (â¼98% and â¼97%, respectively) and achieved concurrent biomethane (â¼94%) and acetate (â¼450 mg/L/d) production. High-throughput 16S rRNA gene amplicon sequencing suggested that enriched microbial communities were dominated by Acetobacterium (38-48% relative abundance). In addition, reverse transcription quantitative PCR of the functional marker gene formyltetrahydrofolate synthetase showed that its expression level increased with increasing H2 and CO2 utilization efficiencies. These results indicate that Acetobacterium plays a key role in CO2 to acetate conversion. These findings are expected to facilitate energy-positive wastewater treatment and contribute to the development of a new solution to biogas upgrading.
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Biopelículas , Biocombustibles , Reactores Biológicos , ARN Ribosómico 16S , Dióxido de Carbono/metabolismo , Acetatos/metabolismoRESUMEN
The microbial oxidation of short-chain gaseous alkanes (SCGAs, consisting of ethane, propane, and butane) serves as an efficient sink to mitigate these gases' emission to the atmosphere, thus reducing their negative impacts on air quality and climate. "Candidatus Alkanivorans nitratireducens" are recently found to mediate nitrate-dependent anaerobic ethane oxidation (n-DAEO). In natural ecosystems, anaerobic ammonium-oxidizing (anammox) bacteria may consume nitrite generated from nitrate reduction by "Ca. A. nitratireducens", thereby alleviating the inhibition caused by nitrite accumulation on the metabolism of "Ca. A. nitratireducens". Here, we demonstrate the coupling of n-DAEO with anammox in a laboratory-scale model system to prevent nitrite accumulation. Our results suggest that a high concentration of ethane (6.9-7.9%) has acute inhibition on anammox activities, thus making the coupling process a significant challenge. By maintaining ethane concentrations within the range of 1.7-5.5%, stable ethane and ammonium oxidation, nitrate reduction, and dinitrogen gas generation without nitrite accumulation were finally achieved. After the accomplished coupling of n-DAEO with anammox, nitrate reduction rates increased by 8.1 times compared to the rate observed with n-DAEO alone. Microbial community profiling via 16S rRNA gene amplicon sequencing showed "Ca. A. nitratireducens" (6.6-12.9%) and anammox bacteria "Candidatus Kuenenia" (3.4-5.6%) were both dominant in the system, indicating they potentially form a syntrophic partnership to jointly contribute to nitrogen removal. Our findings offer insights into the cross-feeding interaction between "Ca. A. nitratireducens" and anammox bacteria in anoxic environments.
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Compuestos de Amonio , Etano , Nitratos , Oxidación-Reducción , Compuestos de Amonio/metabolismo , Anaerobiosis , Nitratos/metabolismo , Etano/metabolismo , Nitritos/metabolismoRESUMEN
This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis. Corresponding to the short hydraulic retention time of 0.25 days, a high chromate removal rate of 80 µmol/L/d was attained. In addition to chromate reduction, in situ production of volatile fatty acids (VFAs) by gas fermentation was observed. Three sets of in situ batch tests and two groups of ex situ batch tests jointly unravelled the mechanisms, showing that biological chromate reduction was primarily driven by VFAs produced from in situ syngas fermentation, whereas hydrogen originally present in the syngas played a minor role. 16 S rRNA gene amplicon sequencing has confirmed the enrichment of syngas-fermenting bacteria (such as Sporomusa), who performed in situ gas fermentation leading to the synthesis of VFAs, and organics-utilising bacteria (such as Aquitalea), who utilised VFAs to drive chromate reduction. These findings, combined with batch assays, elucidate the pathways orchestrating synergistic interactions between fermentative microbial cohorts and chromate-reducing microorganisms. The findings facilitate the development of cost-effective strategies for groundwater and drinking water remediation and present an alternative application scenario for syngas.
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Biopelículas , Reactores Biológicos , Cromatos , Membranas Artificiales , Cromatos/metabolismo , Fermentación , Contaminantes Químicos del Agua/metabolismo , Oxidación-Reducción , Ácidos Grasos Volátiles/metabolismo , Bacterias/metabolismo , Bacterias/genética , Hidrógeno/metabolismo , Gases/metabolismo , Biodegradación AmbientalRESUMEN
The bacterial species "Candidatus Alkanivorans nitratireducens" was recently demonstrated to mediate nitrate-dependent anaerobic oxidation of short-chain gaseous alkanes (SCGAs). In previous bioreactor enrichment studies, the species appeared to reduce nitrate in two phases, switching from denitrification to dissimilatory nitrate reduction to ammonium (DNRA) in response to nitrite accumulation. The regulation of this switch or the nature of potential syntrophic partnerships with other microorganisms remains unclear. Here, we describe anaerobic multispecies cultures of bacteria that couple the oxidation of propane and butane to nitrate reduction and the oxidation of ammonium (anammox). Batch tests with 15N-isotope labelling and multi-omic analyses collectively supported a syntrophic partnership between "Ca. A. nitratireducens" and anammox bacteria, with the former species mediating nitrate-driven oxidation of SCGAs, supplying the latter with nitrite for the oxidation of ammonium. The elimination of nitrite accumulation by the anammox substantially increased SCGA and nitrate consumption rates, whereas it suppressed DNRA. Removing ammonium supply led to its eventual production, the accumulation of nitrite, and the upregulation of DNRA gene expression for the abundant "Ca. A. nitratireducens". Increasing the supply of SCGA had a similar effect in promoting DNRA. Our results suggest that "Ca. A. nitratireducens" switches to DNRA to alleviate oxidative stress caused by nitrite accumulation, giving further insight into adaptability and ecology of this microorganism. Our findings also have important implications for the understanding of the fate of nitrogen and SCGAs in anaerobic environments.
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Alcanos , Compuestos de Amonio , Nitratos , Oxidación-Reducción , Nitratos/metabolismo , Anaerobiosis , Compuestos de Amonio/metabolismo , Alcanos/metabolismo , Consorcios Microbianos , Nitritos/metabolismo , Reactores Biológicos/microbiología , Bacterias/metabolismo , Bacterias/genética , Bacterias/clasificaciónRESUMEN
Methane-dependent denitrification links the global nitrogen and methane cycles. Since its initial discovery in 2006, this process has been understood to involve a division of labor between an archaeal group and a bacterial group, which sequentially perform nitrate and nitrite reduction, respectively. Yao et al. have now revised this paradigm by identifying a Methylomirabilis bacterium capable of performing methane-dependent complete denitrification on its own.
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Archaea , Bacterias , Desnitrificación , Metano , Nitratos , Nitritos , Metano/metabolismo , Desnitrificación/fisiología , Nitratos/metabolismo , Nitritos/metabolismo , Bacterias/metabolismo , Archaea/metabolismo , Oxidación-Reducción , Nitrógeno/metabolismoRESUMEN
The short-chain gaseous alkanes (ethane, propane, and butane; SCGAs) are important components of natural gas, yet their fate in environmental systems is poorly understood. Microbially mediated anaerobic oxidation of SCGAs coupled to nitrate reduction has been demonstrated for propane, but is yet to be shown for ethane or butane-despite being energetically feasible. Here we report two independent bacterial enrichments performing anaerobic ethane and butane oxidation, respectively, coupled to nitrate reduction to dinitrogen gas and ammonium. Isotopic 13C- and 15N-labelling experiments, mass and electron balance tests, and metabolite and meta-omics analyses collectively reveal that the recently described propane-oxidizing "Candidatus Alkanivorans nitratireducens" was also responsible for nitrate-dependent anaerobic oxidation of the SCGAs in both these enrichments. The complete genome of this species encodes alkylsuccinate synthase genes for the activation of ethane/butane via fumarate addition. Further substrate range tests confirm that "Ca. A. nitratireducens" is metabolically versatile, being able to degrade ethane, propane, and butane under anoxic conditions. Moreover, our study proves nitrate as an additional electron sink for ethane and butane in anaerobic environments, and for the first time demonstrates the use of the fumarate addition pathway in anaerobic ethane oxidation. These findings contribute to our understanding of microbial metabolism of SCGAs in anaerobic environments.
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Etano , Nitratos , Etano/metabolismo , Nitratos/metabolismo , Propano/metabolismo , Anaerobiosis , Bacterias/genética , Bacterias/metabolismo , Oxidación-Reducción , Butanos/metabolismo , Gases/metabolismo , Fumaratos/metabolismoRESUMEN
Microbial methane oxidation coupled to a selenate reduction process has been proposed as a promising solution to treat contaminated water, yet the underlying microbial mechanisms are still unclear. In this study, a novel methane-based membrane bioreactor system integrating hollow fiber membranes for efficient gas delivery and ultrafiltration membranes for biomass retention was established to successfully enrich abundant suspended cultures able to perform methane-dependent selenate reduction under oxygen-limiting conditions. The microbial metabolic mechanisms were then systematically investigated through a combination of short-term batch tests, DNA-based stable isotope probing (SIP) microcosm incubation, and high-throughput sequencing analyses of 16S rRNA gene and functional genes (pmoA and narG). We confirmed that the methane-supported selenate reduction process was accomplished by a microbial consortia consisting of type-II aerobic methanotrophs and several heterotrophic selenate reducers. The mass balance and validation tests on possible intermediates suggested that methane was partially oxidized into acetate under oxygen-limiting conditions, which was consumed as a carbon source for selenate-reducing bacteria. High-throughput 16S rRNA gene sequencing, DNA-SIP incubation with 13CH4, and subsequent functional gene (pmoA and narG) sequencing results collectively proved that Methylocystis actively executed partial methane oxidation and Acidovorax and Denitratisoma were dominant selenate-reducing bacteria, thus forming a syntrophic partnership to drive selenate reduction. The findings not only advance our understanding of methane oxidation coupled to selenate reduction under oxygen-limiting conditions but also offer useful information on developing methane-based biotechnology for bioremediation of selenate-contaminated water.
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Bacterias , Metano , Ácido Selénico/metabolismo , ARN Ribosómico 16S/genética , Bacterias/genética , Oxidación-Reducción , Isótopos/metabolismo , Reactores Biológicos , Oxígeno , AguaRESUMEN
Nitrate contamination has been commonly detected in water environments and poses serious hazards to human health. Previously methane was proposed as a promising electron donor to remove nitrate from contaminated water. Compared with pure methane, natural gas, which not only contains methane but also other short chain gaseous alkanes (SCGAs), is less expensive and more widely available, representing a more attractive electron source for removing oxidized contaminants. However, it remains unknown if these SCGAs can be utilized as electron donors for nitrate reduction. Here, two lab-scale membrane biofilm reactors (MBfRs) separately supplied with propane and butane were operated under oxygen-limiting conditions to test its feasibility of microbial nitrate reduction. Long-term performance suggested nitrate could be continuously removed at a rate of â¼40-50 mg N/L/d using propane/butane as electron donors. In the absence of propane/butane, nitrate removal rates significantly decreased both in the long-term operation (â¼2-10 and â¼4-9 mg N/L/d for propane- and butane-based MBfRs, respectively) and batch tests, indicating nitrate bio-reduction was driven by propane/butane. The consumption rates of nitrate and propane/butane dramatically decreased under anaerobic conditions, but recovered after resupplying limited oxygen, suggesting oxygen was an essential triggering factor for propane/butane-based nitrate reduction. High-throughput sequencing targeting 16S rRNA, bmoX and narG genes indicated Mycobacterium/Rhodococcus/Thauera were the potential microorganisms oxidizing propane/butane, while various denitrifiers (e.g. Dechloromonas, Denitratisoma, Zoogloea, Acidovorax, Variovorax, Pseudogulbenkiania and Rhodanobacter) might perform nitrate reduction in the biofilms. Our findings provide evidence to link SCGA oxidation with nitrate reduction under oxygen-limiting conditions and may ultimately facilitate the design of cost-effective techniques for ex-situ groundwater remediation using natural gas.
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Nitratos , Propano , Humanos , Gas Natural , ARN Ribosómico 16S , Alcanos , Metano , Butanos , Oxidación-Reducción , Biopelículas , Oxígeno , Agua , Reactores BiológicosRESUMEN
Anaerobic microorganisms are thought to play a critical role in regulating the flux of short-chain gaseous alkanes (SCGAs; including ethane, propane and butane) from terrestrial and aquatic ecosystems to the atmosphere. Sulfate has been confirmed to act as electron acceptor supporting microbial anaerobic oxidation of SCGAs, yet several other energetically more favourable acceptors co-exist with these gases in anaerobic environments. Here, we show that a bioreactor seeded with biomass from a wastewater treatment facility can perform anaerobic propane oxidation coupled to nitrate reduction to dinitrogen gas and ammonium. The bioreactor was operated for more than 1000 days, and we used 13C- and 15N-labelling experiments, metagenomic, metatranscriptomic, metaproteomic and metabolite analyses to characterize the microbial community and the metabolic processes. The data collectively suggest that a species representing a novel order within the bacterial class Symbiobacteriia is responsible for the observed nitrate-dependent propane oxidation. The closed genome of this organism, which we designate as 'Candidatus Alkanivorans nitratireducens', encodes pathways for oxidation of propane to CO2 via fumarate addition, and for nitrate reduction, with all the key genes expressed during nitrate-dependent propane oxidation. Our results suggest that nitrate is a relevant electron sink for SCGA oxidation in anaerobic environments, constituting a new microbially-mediated link between the carbon and nitrogen cycles.
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Compuestos de Amonio , Nitratos , Alcanos/metabolismo , Anaerobiosis , Butanos , Carbono , Dióxido de Carbono , Ecosistema , Etano/metabolismo , Fumaratos , Metano/metabolismo , Nitratos/metabolismo , Oxidación-Reducción , Propano/metabolismo , Sulfatos/metabolismoRESUMEN
The present study demonstrated that the perchlorate reduction rate in a methane-based membrane biofilm reactor was significantly enhanced from 14.4 to 25.6 mg-Cl/L/d by increasing copper concentration in the feeding medium from 1 to 10 µM, indicating a stimulatory effect of copper on the methane-supported perchlorate reduction process. Batch tests further confirmed that the increased copper concentration enhanced both methane oxidation and perchlorate reduction rates, which was supported by an increasing trend of functional genes (pmoA for methanotrophs and pcrA for specific perchlorate reducers) abundances through quantitative polymerase chain reaction (qPCR). Both 16S rRNA gene sequencing and functional genes (pmoA and pcrA) sequencing jointly revealed that the biofilm supplied with a higher copper concentration exhibited a more diverse microbial community. The methane-supported perchlorate reduction was accomplished through a synergistic association of methanotrophs (Methylocystis, Methylomonas, and Methylocystaceae) and perchlorate reducers (Dechloromonas, Azospira, Magnetospirillum, and Denitratisoma). Acetate may function as the key syntrophic linkage between methanotrophs and perchlorate reducers. It was proposed that the increased copper concentration improved the activity of particulate methane monooxygenase (pMMO) for methane oxidation or promoted the biosynthesis of intracellular carbon storage compounds polyhydroxybutyrate (PHB) in methanotrophs for generating more acetate available for perchlorate reduction.
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Metano , Percloratos , Biopelículas , Reactores Biológicos , Cobre , Oxidación-Reducción , Oxigenasas , ARN Ribosómico 16S/genéticaRESUMEN
Short chain gaseous alkanes (SCGAs) mainly consist of methane (CH4), ethane (C2H6), propane (C3H8) and butane (C4H10). The first three SCGAs have been shown to remove perchlorate (ClO4-) and selenate (SeO42-), yet it is unknown whether C4H10 is available to reduce these contaminants. This study demonstrated that C4H10 fed biofilms were capable of reducing ClO4- and SeO42- to chloride (Cl-) and elemental selenium (Se0), respectively, by employing two independent membrane biofilms reactors (MBfRs). Batch tests showed that C4H10 and oxygen fed biofilms had much higher ClO4- and SeO42- reduction rates and enhanced expression levels of bmoX and pcrA than that without C4H10 or O2. Polyhydroxyalkanoates (PHA) accumulated in the biofilms when C4H10 was supplied, and they decomposed for driving ClO4- and SeO42- reduction when C4H10 was absent. Moreover, we revisited the literature and found that a cross-feeding pathway seems to be universal in microaerobic SCGA-driven perchlorate and selenate reduction processes. In the ClO4--reducing MBfRs, Mycobacterium primarily conducts C2H6 and C3H8 oxidation in synergy with Dechloromonas who performs perchlorate reduction, while both Mycobacterium and Rhodococcus carried out C4H10 oxidation with perchlorate-respiring Azospira as the partner. In the SeO42--reducing MBfRs, Mycobacterium oxidized C2H6 solely or oxidized C3H8 jointly with Rhodococcus, while Burkholderiaceae likely acted as the selenate-reducing bacterium. When C4H10 was supplied as the electron donor, both Mycobacterium and Rhodococcus conducted C4H10 oxidation in synergy with unknow selenate-reducing bacterium. Collectively, we confirm that from CH4 to C4H10, all SCGAs could be utilized as electron donors for bio-reduction process. These findings offer insights into SCGA-driven bio-reduction processes, and are helpful in establishing SCGA-based technologies for groundwater remediation.
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Reactores Biológicos , Percloratos , Alcanos , Biopelículas , Gases , Oxidación-Reducción , Ácido SelénicoRESUMEN
Although methane (CH4) has been proven to be able to serve as an electron donor for bio-reducing various oxidized contaminants (e.g., selenate (SeO42-)), little is known regarding the roles of oxygen in methane-based reduction processes. Here, a methane-based membrane biofilm reactor (MBfR) was established for evaluating the effects of oxygen supply rates on selenate reduction performance and microbial communities. The oxygen supply rate played a dual role (stimulatory or suppressive effect) in selenate reduction rates, depending on the presence or absence of dissolved oxygen (DO). Specifically, selenate reduction rate was substantially enhanced when an appropriate oxygen rate (e.g., 12 to 184 mg/L.d in this study) was supplied but with negligible DO. The highest selenate reduction rate (up to 34 mg-Se/L.d) was obtained under an oxygen supply rate of 184 mg/L.d. In contrast, excessive oxygen supply rate (626 mg/L.d) would significantly suppress selenate reduction rate under DO level of 3 mg/L. Accordingly, though the high oxygen supply rate (626 mg/L.d) would promote the expression of pmoA (5.9 × 109 copies g-1), the expression level of narG (a recognized gene to mediate selenate reduction) would be significantly downregulated (6.1 × 109 copies g-1), thus suppressing selenate reduction. In contrast, the expression of narG gene significantly increased to 2.8 × 1010 copies g-1, and the expression of pmoA gene could still maintain at 1.1 × 109 copies g-1 under an oxygen supply rate of 184 mg/L.d. High-throughput sequencing targeting 16S rRNA gene, pmoA, and narG collectively suggested Methylocystis acts as the major aerobic methanotroph, in synergy with Arthrobacter and Variovorax which likely jointly reduce selenate to selenite (SeO32-), and further to elemental selenium (Se0). Methylocystis was predominant in the biofilm regardless of variations of oxygen supply rates, while Arthrobacter and Variovorax were sensitive to oxygen fluctuation. These findings provide insights into the effects of oxygen on methane-dependent selenate reduction and suggest that it is feasible to achieve a higher selenate removal by regulating oxygen supply rates.
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Metano , Oxígeno , Biopelículas , Reactores Biológicos , Oxidación-Reducción , ARN Ribosómico 16S/genética , Ácido SelénicoRESUMEN
Being an energetic fuel, methane is able to support microbial growth and drive the reduction of various electron acceptors. These acceptors include a broad range of oxidized contaminants (e.g., nitrate, nitrite, perchlorate, bromate, selenate, chromate, antimonate and vanadate) that are ubiquitously detected in water environments and pose threats to human and ecological health. Using methane as electron donor to biologically reduce these contaminants into nontoxic forms is a promising solution to remediate polluted water, considering that methane is a widely available and inexpensive electron donor. The understanding of methane-based biological reduction processes and the responsible microorganisms has grown in the past decade. This review summarizes the fundamentals of metabolic pathways and microorganisms mediating microbial methane oxidation. Experimental demonstrations of methane as an electron donor to remove oxidized contaminants are summarized, compared, and evaluated. Finally, the review identifies opportunities and unsolved questions that deserve future explorations for broadening understanding of methane oxidation and promoting its practical applications.
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Metano , Aguas Residuales , Anaerobiosis , Biopelículas , Reactores Biológicos , Desnitrificación , Humanos , Oxidación-ReducciónRESUMEN
Previous studies demonstrated that methane can be used as an electron donor to microbially remove various oxidized contaminants in groundwater. Natural gas, which is more widely available and less expensive than purified methane, is potentially an alternative source of methane. However, natural gas commonly contains a considerable amount of ethane (C2H6) and propane (C3H8), in addition to methane. It is important that these gaseous alkanes are also utilized along with methane to avoid emissions. Here, we demonstrate that perchlorate (ClO4-), a frequently reported contaminant in groundwater, can be microbially reduced to chloride (Cl-) driven by C2H6 or C3H8 under oxygen-limiting conditions. Two independent membrane biofilm reactors (MBfRs) supplied with C2H6 and C3H8, respectively, were operated in parallel to biologically reduce ClO4-. The continuous ClO4- removal during long-term MBfR operation combined with the concurrent C2H6/C3H8 consumption and ClO4- reduction in batch tests confirms that ClO4- reduction was associated with C2H6 or C3H8 oxidation. Polyhydroxyalkanoates (PHAs) were synthesized in the presence of C2H6 or C3H8 and were subsequently utilized for supporting ClO4- bio-reduction in the absence of gaseous alkanes. Analysis by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) showed that transcript abundance of bmoX (encoding alpha hydroxylase subunit of C2H6/C3H8 monooxygenase) was positively correlated to the consumption rates of C2H6/C3H8, while pcrA (encoding a catalytic subunit of perchlorate reductase) was positively correlated to the consumption of ClO4-. High-throughput sequencing targeting 16S rRNA, bmoX, and pcrA indicated that Mycobacterium was the dominant microorganism oxidizing C2H6/C3H8, while Dechloromonas may be the major perchlorate-reducing bacterium in the biofilms. These findings shed light on microbial ClO4- reduction driven by C2H6 and C3H8, facilitating the development of cost-effective strategies for ex situ groundwater remediation.
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Etano , Percloratos , Reactores Biológicos , Oxidación-Reducción , Propano , ARN Ribosómico 16S/genéticaRESUMEN
Importance: Schools have been suspended nationwide in 188 countries, and classes have shifted to home-based distance learning models to control the spread of the coronavirus disease 2019 (COVID-19) pandemic. Additional information is needed to determine mental health status among school-aged children and adolescents during this public health crisis and the risk factors associated with psychological distress during the pandemic. Objective: To assess self-reported psychological distress among school-aged children and adolescents associated with the COVID-19 pandemic. Design, Setting, and Participants: This cross-sectional study using data from a survey on the mental health of school-aged children and adolescents in Guangdong province, China, conducted by using a stratified cluster random sampling method between March 8 to 30, 2020. To estimate outcomes associated with location of districts, only data from students with internet protocol addresses and current addresses in Guangdong were included. Data were analyzed from April 5 to July 20, 2020. Exposure: Home-based distance learning during the COVID-19 pandemic. Main Outcome and Measures: The main outcome was self-reported psychological distress, measured using the total score on the 12-item General Health Questionnaire of 3 or greater. Multivariate logistic regression was used to analyze risk factors associated with mental health status. Odds ratios (ORs) were used to analyze the associations of factors with psychological distress. Results: Among 1â¯310â¯600 students who completed the survey, 1â¯199â¯320 students (mean [SD] age, 12.04 [3.01] years; 619â¯144 [51.6%] boys) were included in the final analysis. A total of 126â¯355 students (10.5%) self-reported psychological distress. Compared with students in primary school, high school students had increased risk of psychological distress (OR, 1.19 [95% CI, 1.15-1.23]). Compared with students who wore a face mask frequently, students who never wore a face mask had increased risk of psychological distress (OR, 2.59 [95% CI, 2.41-2.79]). Additionally, students who spent less than 0.5 hours exercising had increased odds of self-reported psychological distress compared with students who spent more than 1 hour exercising (OR, 1.64 [95% CI, 1.61-1.67]). Conclusions and Relevance: These findings suggest that the prevalence of self-reported psychological distress among students during the COVID-19 pandemic was relatively high. Frequency of wearing a face mask and time spent exercising were factors associated with mental health. Therefore, it may be necessary for governments, schools, and families to pay attention to the mental health of school-aged children and adolescents during the COVID-19 pandemic and take corresponding countermeasures to reduce the impact of the COVID-19 pandemic on students' mental health.
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Ansiedad/etiología , COVID-19/psicología , Depresión/etiología , Salud Mental , Pandemias , Distrés Psicológico , Estrés Psicológico/etiología , Adolescente , Ansiedad/epidemiología , Niño , China/epidemiología , Estudios Transversales , Depresión/epidemiología , Ejercicio Físico , Femenino , Humanos , Modelos Logísticos , Masculino , Máscaras , Oportunidad Relativa , Prevalencia , Factores de Riesgo , SARS-CoV-2 , Instituciones Académicas , Autoinforme , Estrés Psicológico/epidemiología , EstudiantesRESUMEN
Although remediation of toxic vanadium (V) [V(V)] pollution can be achieved through either heterotrophic or sulfur-based autotrophic microbial reduction, these processes would require a large amount of organic carbons or generate excessive sulfate. This study reported that by using mixotrophic V(V) bio-reduction with acetate and elemental sulfur [S(0)] as joint electron donors, V(V) removal performance was enhanced due to cooccurrence of heterotrophic and autotrophic activities. Deposited vanadium (IV) was identified as the main reduction product by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Based on 16S rRNA gene amplicon sequencing, qPCR and genus-specific reverse transcription qPCR, it was observed that V(V) was likely detoxified by heterotrophic V(V) reducers (e.g., Syntrophobacter, Spirochaeta and Geobacter). Cytochrome c, intracellular nicotinamide adenine dinucleotide and extracellular polymeric substances were involved in V(V) reduction and binding. Organic metabolites synthesized by autotrophs (e.g., Thioclava) with energy from S(0) oxidation might compensate electron donors for heterotrophic V(V) and sulfate reducers. Less sulfate was accumulated presumably due to activities of sulfur-respiring genera (e.g., Desulfurella). This study demonstrates mixotrophic microbial V(V) reduction can save organic dosage and avoid excessive sulfate accumulation, which will be beneficial to bioremediation of V(V) contamination.
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Azufre , Vanadio , Procesos Autotróficos , Reactores Biológicos , Oxidación-Reducción , ARN Ribosómico 16S/genética , SulfatosRESUMEN
Understanding the recovery of anaerobic ammonium-oxidizing (anammox) bacteria after inhibition by dissolved oxygen (DO) is critical for the successful applications of anammox-based processes. Therefore, the effects of oxygen exposure (2 mg L-1 DO for 90 min) and subsequent recovery treatments [N2 purging or nano zero-valent iron (nZVI) addition] on the activity and gene expression in a Kuenenia stuttgartiensis enrichment culture were examined. Combining the self-organizing map clustering and enrichment analysis, we proposed the oxidative stress response of anammox bacteria based on the existing concepts of oxidative stress in microbes: the DO exposure triggered a stringent response in K. stuttgartiensis, which downregulated the transcription levels of genes involved in the central metabolism and diverted energy to a flagellar assembly and metal transport modules; these changes possibly promoted survival during the inhibition of anammox activity. According to the cotranscription with central catabolism genes, putative reactive oxygen species (ROS) scavenger genes (kat and sod) were presumed to detoxify the anammox intermediates rather than ROS. In addition, both activity and mRNA profiles with appropriate amount of nZVI addition (5 and 25 mg L-1) were close to that of control, which proved the effectiveness of nZVI addition in anammox recovery. These results would be relevant to the physio-biochemistry development of anammox bacteria and further enhancement of nitrogen removal in wastewater treatment.
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Compuestos de Amonio , Oxígeno , Anaerobiosis , Bacterias/genética , Reactores Biológicos , Crecimiento Quimioautotrófico , Nitrógeno , Oxidación-Reducción , TranscriptomaRESUMEN
Selenate (Se(VI)) contamination in groundwater is one of major concerns for human health, in particular in shale gas extraction sites. Microbial selenate reduction coupled to methane (CH4) oxidation has been demonstrated very recently. Little is known whether ethane (C2H6) and butane (C3H8) are able to drive selenate reduction, although they are also important components in shale gas. In this study, we demonstrated Se(VI) bio-reduction could be achieved using C2H6 and C3H8 as electron donors and carbon sources. Scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDX) confirmed elemental Se (Se0) was the major final product formed from Se(VI) bio-reduction. Polyhydroxyalkanoates (PHAs) were generated in the biofilms as the internal electron-storage materials, which were consumed for sustaining Se(VI) bio-reduction in absence of C2H6 and C3H8. Microbial community analysis showed that two genera capable of oxidizing gaseous alkanes dominated in the biofilms, including Mycobacterium (in both C2H6 and C3H8-fed biofilms) and Rhodococcus (in C3H8-fed biofilm). In addition, several potential Se(VI) reducers (e.g., Variovorax) were detected in the biofilms. Investigation of Communities by Reconstruction of Unobserved States analysis supported that predictive genes associated with alkanes oxidation, denitrification and PHAs cycle were enriched in the biofilms. These findings offer insights into the process of selenate reduction driven by C2H6 and C3H8, which ultimately may help to develop a solution to use shale gas for groundwater remediation, especially near shale gas exploitation sites.
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Etano , Propano , Biopelículas , Reactores Biológicos , Electrones , Oxidación-Reducción , Ácido SelénicoRESUMEN
It has been reported that microbial reduction of sulfate, nitrite/nitrate and iron/manganese could be coupled with anaerobic oxidation of methane (AOM), which plays a significant role in controlling methane emission from anoxic niches. However, little is known about microbial chromate (Cr(VI)) reduction coupling with AOM. In this study, a microbial consortium was enriched via switching nitrate dosing to chromate feeding as the sole electron acceptor under anaerobic condition in a membrane biofilm reactor (MBfR), in which methane was continuously provided as the electron donor through bubble-less hollow fiber membranes. According to long-term reactor operation and chromium speciation analysis, soluble chromate could be reduced into Cr(III) compounds by using methane as electron donor. Fluorescence in situ hybridization and high-throughput 16S rRNA gene amplicon profiling further indicated that after feeding chromate Candidatus 'Methanoperedens' (a known nitrate-dependent anaerobic methane oxidation archaeon) became sole anaerobic methanotroph in the biofilm, potentially responsible for the chromate bio-reduction driven by methane. Two potential pathways of the microbial AOM-coupled chromate reduction were proposed: (i) Candidatus 'Methanoperedens' independently utilizes chromate as electron acceptor to form Cr(III) compounds, or (ii) Candidatus 'Methanoperedens' oxidizes methane to generate intermediates or electrons, which will be utilized to reduce chromate to Cr(III) compounds by unknown chromate reducers synergistically. Our findings suggest a possible link between the biogeochemical chromium and methane cycles.