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1.
Chemosphere ; 239: 124823, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726520

RESUMO

Several studies have demonstrated that gypsum (CaSO4·2H2O) and calcite (CaCO3) can be important hosts of arsenic in contaminated hydrogeological systems. However, the extent to which microbial reducing processes contribute to the dissolution and transformation of carbonate and sulfate minerals and, thereby, to arsenic mobilization is poorly understood. These processes are likely to have a strong impact on arsenic mobility in iron-poor environments and in reducing aquifers where iron oxyhydroxides become unstable. Anoxic batch bioassays with arsenate (As(V)) coprecipitated with calcite, gypsum, or ferrihydrite (Fe(OH)3) were conducted in the presence of sulfate or molybdate to examine the impact of bioprocesses (i.e. As(V), sulfate, and Fe(III)-reduction) on arsenic dissolution, speciation, and eventual remineralization. Microbial reduction of As(V)-bearing calcite caused an important dissolution of arsenite, As(III), which remained in solution up to the end of the experiment (30 days). The reduction of As(V) from gypsum-As(V) also led to the release of As(III), which was subsequently remineralized, possibly as arsenic sulfides. The presence of sulfate triggered arsenic dissolution in the bioassays with ferrihydrite-As(V). This study showed that although gypsum and calcite have a lower capacity to bind arsenic, compared to iron oxides, they can play a critical role in the biogeochemical cycle of arsenic in natural calcareous and gypsiferous systems depleted of iron since they can be a source of electron acceptors for reducing bioprocesses.


Assuntos
Arsênico/química , Bactérias/metabolismo , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Compostos Férricos/química , Arseniatos/química , Arsenicais/química , Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Ferro/química , Molibdênio/química , Oxirredução , Solubilidade , Sulfatos/química , Sulfetos/química
2.
Biodegradation ; 29(5): 429-442, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29948518

RESUMO

Availability of fixed nitrogen is a pivotal driver on primary productivity in the oceans, thus the identification of key processes triggering nitrogen losses from these ecosystems is of major importance as they affect ecosystems function and consequently global biogeochemical cycles. Denitrification and anaerobic ammonium oxidation coupled to nitrite reduction (Anammox) are the only identified marine sinks for fixed nitrogen. The present study provides evidence indicating that anaerobic ammonium oxidation coupled to the reduction of sulfate, the most abundant electron acceptor present in the oceans, prevails in marine sediments. Tracer analysis with 15N-ammonium revealed that this microbial process, here introduced as Sulfammox, accounts for up to 5 µg 15N2 produced g-1 day-1 in sediments collected from the eastern tropical North Pacific coast. Raman and X-ray diffraction spectroscopies revealed that elemental sulfur and sphalerite (ZnFeS) were produced, besides free sulfide, during the course of Sulfammox. Anaerobic ammonium oxidation linked to Fe(III) reduction (Feammox) was also observed in the same marine sediments accounting for up to 2 µg 15N2 produced g-1 day-1. Taxonomic characterization, based on 16S rRNA gene sequencing, of marine sediments performing the Sulfammox and Feammox processes revealed the microbial members potentially involved. These novel nitrogen sinks may significantly fuel nitrogen loss in marine environments. These findings suggest that the interconnections among the oceanic biogeochemical cycles of N, S and Fe are much more complex than previously considered.


Assuntos
Compostos de Amônio/metabolismo , Compostos Férricos/metabolismo , Sedimentos Geológicos/química , Nitrogênio/análise , Água do Mar/microbiologia , Sulfatos/metabolismo , Anaerobiose , Bactérias/metabolismo , Biodegradação Ambiental , Elétrons , Ferro/análise , Oxirredução , Enxofre/metabolismo
3.
Microb Ecol ; 75(4): 930-940, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29116347

RESUMO

Methanogenesis and sulfate reduction are important microbial processes in hypersaline environments. However, key aspects determining substrate competition between these microbial processes have not been well documented. We evaluated competitive and non-competitive substrates for stimulation of both processes through microcosm experiments of hypersaline microbial mat samples from Guerrero Negro, Baja California Sur, Mexico, and we assessed the effect of these substrates on the microbial community composition. Methylotrophic methanogenesis evidenced by sequences belonging to methanogens of the family Methanosarcinaceae was found as the dominant methanogenic pathway in the studied hypersaline microbial mat. Nevertheless, our results showed that incubations supplemented with acetate and lactate, performed in absence of sulfate, also produced methane after 40 days of incubation, apparently driven by hydrogenotrophic methanogens affiliated to the family Methanomicrobiaceae. Sulfate reduction was mainly stimulated by addition of acetate and lactate; however, after 40 days of incubation, an increase of the H2S concentrations in microcosms amended with trimethylamine and methanol was also observed, suggesting that these substrates are putatively used for sulfate reduction. Moreover, 16S rRNA gene sequencing analysis showed remarkable differences in the microbial community composition among experimental treatments. In the analyzed sample amended with acetate, sulfate-reducing bacteria (SRB) belonging to the family Desulfobacteraceae were dominant, while members of Desulfohalobiaceae, Desulfomicrobiaceae, and Desulfovibrionaceae were found in the incubation with lactate. Additionally, we detected an unexpected high abundance of unclassified Hydrogenedentes (near 25%) in almost all the experimental treatments. This study contributes to better understand methanogenic and sulfate-reducing activities, which play an important role in the functioning of hypersaline environments.


Assuntos
Bactérias/metabolismo , Crescimento Quimioautotrófico , Metano/metabolismo , Microbiota/fisiologia , Salinidade , Sulfatos/metabolismo , Bactérias/classificação , Bactérias/genética , Biodiversidade , Sulfeto de Hidrogênio/metabolismo , Metilaminas/metabolismo , México , Microbiota/genética , Filogenia , RNA Ribossômico 16S/genética
4.
Antonie Van Leeuwenhoek ; 110(11): 1453-1465, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28608318

RESUMO

Considering the great agronomic and environmental importance of denitrification, the aim of the present study was to study the temporal and spatial factors controlling the abundance and activity of denitrifying bacterial communities in a range of eight agricultural soils over 2 years. Abundance was quantified by qPCR of the nirS, nirK and nosZ genes, and the potential denitrification enzyme activity (DEA) was estimated. Our data showed a significant temporal variation considerably high for the abundance of nirK-harboring communities, followed by nosZ and nirS communities. Regarding soil parameters, the abundances of nosZ, nirS and nirK were mostly influenced by organic material, pH, and slightly by NO3-, respectively. Soil texture was the most important factor regulating DEA, which could not be explained by the abundance of denitrifiers. Analyses of general patterns across lands to understand the soil functioning is not an easy task because the multiple factors influencing processes such as denitrification can skew the data. Careful analysis of atypical sites are necessary to classify the soils according to trait similarity and in this way reach a better predictability of the denitrifiers dynamics.


Assuntos
Bactérias/enzimologia , Desnitrificação/fisiologia , Nitrito Redutases/metabolismo , Microbiologia do Solo , Solo/química , Agricultura , Genes Bacterianos/genética , Países Baixos , Nitrito Redutases/genética , Reação em Cadeia da Polimerase em Tempo Real , Análise de Regressão , Análise Espaço-Temporal
5.
Bioresour Technol ; 238: 528-533, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28475995

RESUMO

A novel reactor configuration for the enrichment of anammox bacteria from marine sediments was developed. Marine sediments were successfully kept inside the bioreactors during the enrichment process by strategically installing traps at different depths to prevent the wash-out of sediments. Three up-flow anaerobic sediment trapped (UAST) reactors were set up (α, ß and ω supplied with 50, 150 and 300mgCa2+/L, respectively). Nitrogen removal rates (NRR) of up to 3.5gN/L-d and removal efficiencies of >95% were reached. Calcium enhanced biomass production as evidenced by increased volatile suspended solids and extracellular polymeric substances. After the long-term operation, dominant families detected were Rhodobacteracea, Flavobacteracea, and Alteromonadacea, while the main anammox genera detected in the three reactors were Candidatus Kuenenia and Candidatus Anammoximicrobium. The UAST reactor is proposed as suitable technology for the enrichment of anammox bacteria applicable for the treatment of saline industrial wastewaters with high nitrogen content.


Assuntos
Reatores Biológicos , Sedimentos Geológicos , Bactérias , Bactérias Anaeróbias , Crescimento Quimioautotrófico , Nitrogênio , Oxirredução
6.
Appl Environ Microbiol ; 83(11)2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28341676

RESUMO

Wetlands constitute the main natural source of methane on Earth due to their high content of natural organic matter (NOM), but key drivers, such as electron acceptors, supporting methanotrophic activities in these habitats are poorly understood. We performed anoxic incubations using freshly collected sediment, along with water samples harvested from a tropical wetland, amended with 13C-methane (0.67 atm) to test the capacity of its microbial community to perform anaerobic oxidation of methane (AOM) linked to the reduction of the humic fraction of its NOM. Collected evidence demonstrates that electron-accepting functional groups (e.g., quinones) present in NOM fueled AOM by serving as a terminal electron acceptor. Indeed, while sulfate reduction was the predominant process, accounting for up to 42.5% of the AOM activities, the microbial reduction of NOM concomitantly occurred. Furthermore, enrichment of wetland sediment with external NOM provided a complementary electron-accepting capacity, of which reduction accounted for ∼100 nmol 13CH4 oxidized · cm-3 · day-1 Spectroscopic evidence showed that quinone moieties were heterogeneously distributed in the wetland sediment, and their reduction occurred during the course of AOM. Moreover, an enrichment derived from wetland sediments performing AOM linked to NOM reduction stoichiometrically oxidized methane coupled to the reduction of the humic analogue anthraquinone-2,6-disulfonate. Microbial populations potentially involved in AOM coupled to microbial reduction of NOM were dominated by divergent biota from putative AOM-associated archaea. We estimate that this microbial process potentially contributes to the suppression of up to 114 teragrams (Tg) of CH4 · year-1 in coastal wetlands and more than 1,300 Tg · year-1, considering the global wetland area.IMPORTANCE The identification of key processes governing methane emissions from natural systems is of major importance considering the global warming effects triggered by this greenhouse gas. Anaerobic oxidation of methane (AOM) coupled to the microbial reduction of distinct electron acceptors plays a pivotal role in mitigating methane emissions from ecosystems. Given their high organic content, wetlands constitute the largest natural source of atmospheric methane. Nevertheless, processes controlling methane emissions in these environments are poorly understood. Here, we provide tracer analysis with 13CH4 and spectroscopic evidence revealing that AOM linked to the microbial reduction of redox functional groups in natural organic matter (NOM) prevails in a tropical wetland. We suggest that microbial reduction of NOM may largely contribute to the suppression of methane emissions from tropical wetlands. This is a novel avenue within the carbon cycle in which slowly decaying NOM (e.g., humic fraction) in organotrophic environments fuels AOM by serving as a terminal electron acceptor.


Assuntos
Bactérias/metabolismo , Metano/metabolismo , Anaerobiose , Antraquinonas/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Oxirredução , Áreas Alagadas
7.
PeerJ ; 1: e47, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23638384

RESUMO

Ecological succession is one of the most important concepts in ecology. However for microbial community succession, there is a lack of a solid theoretical framework regarding succession in microorganisms. This is in part due to microbial community complexity and plasticity but also because little is known about temporal patterns of microbial community shifts in different kinds of ecosystems, including arid soils. The Cuatro Cienegas Basin (CCB) in Coahuila, Mexico, is an arid zone with high diversity and endemisms that has recently been threatened by aquifer overexploitation. The gypsum-based soil system of the CCB is one of the most oligotrophic places in the world. We undertook a comparative 16S rRNA 454 pyrosequencing study to evaluate microbial community succession and recovery over a year after disturbance at two sites. Results were related to concurrent measurements of humidity, organic matter and total C and N content. While each site differed in both biogeochemistry and biodiversity, both present similar pattern of change at the beginning of the succession that diverged in later stages. After one year, experimentally disturbed soil was not similar to established and undisturbed adjacent soil communities indicating recovery and succession in disturbed soils is a long process.

8.
Astrobiology ; 12(7): 699-709, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22920518

RESUMO

The OMEGA/Mars Express hyperspectral imager identified gypsum at several sites on Mars in 2005. These minerals constitute a direct record of past aqueous activity and are important with regard to the search of extraterrestrial life. Gale Crater was chosen as Mars Science Laboratory Curiosity's landing site because it is rich in gypsum, as are some desert soils of the Cuatro Ciénegas Basin (CCB) (Chihuahuan Desert, Mexico). The gypsum of the CCB, which is overlain by minimal carbonate deposits, was the product of magmatic activity that occurred under the Tethys Sea. To examine this Mars analogue, we retrieved gypsum-rich soil samples from two contrasting sites with different humidity in the CCB. To characterize the site, we obtained nutrient data and analyzed the genes related to the N cycle (nifH, nirS, and nirK) and the bacterial community composition by using 16S rRNA clone libraries. As expected, the soil content for almost all measured forms of carbon, nitrogen, and phosphorus were higher at the more humid site than at the drier site. What was unexpected is the presence of a rich and divergent community at both sites, with higher taxonomic diversity at the humid site and almost no taxonomic overlap. Our results suggest that the gypsum-rich soils of the CCB host a unique microbial ecosystem that includes novel microbial assemblies.


Assuntos
Bactérias/crescimento & desenvolvimento , Sulfato de Cálcio/química , Exobiologia , Marte , Consórcios Microbianos , Ciclo do Nitrogênio , Solo/química , Bactérias/classificação , Bactérias/genética , Intervalos de Confiança , Desnitrificação/genética , Biblioteca Gênica , Genes Bacterianos/genética , México , Consórcios Microbianos/genética , Dados de Sequência Molecular , Ciclo do Nitrogênio/genética , Fixação de Nitrogênio/genética , Filogenia , RNA Ribossômico 16S/genética , Microbiologia do Solo
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