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The ISME Journal Apr 2021Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often...
Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often characterized by co-burial of iron oxides with recalcitrant aromatic organic matter of terrigenous origin. Thus far, iron oxides are predicted to either impede organic matter degradation, aiding its preservation, or identified to enhance organic carbon oxidation via direct electron transfer. Here, we investigated the effect of various iron oxide phases with differing crystallinity (magnetite, hematite, and lepidocrocite) during microbial degradation of the aromatic model compound benzoate in methanic sediments. In slurry incubations with magnetite or hematite, concurrent iron reduction, and methanogenesis were stimulated during accelerated benzoate degradation with methanogenesis as the dominant electron sink. In contrast, with lepidocrocite, benzoate degradation, and methanogenesis were inhibited. These observations were reproducible in sediment-free enrichments, even after five successive transfers. Genes involved in the complete degradation of benzoate were identified in multiple metagenome assembled genomes. Four previously unknown benzoate degraders of the genera Thermincola (Peptococcaceae, Firmicutes), Dethiobacter (Syntrophomonadaceae, Firmicutes), Deltaproteobacteria bacteria SG8_13 (Desulfosarcinaceae, Deltaproteobacteria), and Melioribacter (Melioribacteraceae, Chlorobi) were identified from the marine sediment-derived enrichments. Scanning electron microscopy (SEM) and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) images showed the ability of microorganisms to colonize and concurrently reduce magnetite likely stimulated by the observed methanogenic benzoate degradation. These findings explain the possible contribution of organoclastic reduction of iron oxides to the elevated dissolved Fe pool typically observed in methanic zones of rapidly accumulating coastal and continental margin sediments.
Topics: Benzoates; Ferric Compounds; Geologic Sediments; In Situ Hybridization, Fluorescence; Iron; Oxidation-Reduction; Oxides
PubMed: 33154547
DOI: 10.1038/s41396-020-00824-7 -
Nature Communications Oct 2020Nickel-iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel-iron hydroxides. The...
Nickel-iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel-iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel-iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies.
Topics: Corrosion; Density Functional Theory; Desulfotomaculum; Electrochemistry; Electrodes; Hydroxides; Nickel; Oxygen; Spectrum Analysis, Raman; X-Ray Absorption Spectroscopy
PubMed: 33033245
DOI: 10.1038/s41467-020-18891-x -
Microorganisms Jul 2020The aim was to assess the gut microbiota of long-livers from Moscow. This study included two groups of patients who signed their consent to participate. The group of...
The aim was to assess the gut microbiota of long-livers from Moscow. This study included two groups of patients who signed their consent to participate. The group of long-livers (LL) included 20 participants aged 97-100 years (4 men and 16 women). The second group included 22 participants aged 60-76 years (6 men) without clinical manifestations of chronic diseases (healthy elderly). Gut microbiota was studied by 16S rRNA sequencing. Long-livers underwent a complex geriatric assessment as well as expanded blood biochemistry. Gut microbiota composition in the cohorts was also compared with microbiome in long-livers from Japan and Italy. Russian long-livers' microbiome contained more beneficial bacteria than healthy elderly including families. Conditional pathogens like were more abundant in the healthy elderly. Compared with Italian and Japanese microbiome LL, the Russian LL appeared to be more similar to the Italian cohort. and balances were associated with femoral and carotid intima-media thickness, respectively. balance was assessed with the folic acid level and the with Mini Nutritional Assessment score. Long-livers' microbiome appeared to be unexpectedly balanced. The high representation of beneficial bacteria in long-livers may prevent them from low-grade inflammation and thus protect them from the development of atherosclerosis and other aging-associated conditions.
PubMed: 32751673
DOI: 10.3390/microorganisms8081162 -
Toxins Jun 2020Trichothecenes are the most common mycotoxins contaminating small grain cereals worldwide. The C12,13 epoxide group in the trichothecenes was identified as a toxic group...
Trichothecenes are the most common mycotoxins contaminating small grain cereals worldwide. The C12,13 epoxide group in the trichothecenes was identified as a toxic group posing harm to humans, farm animals, and plants. Aerobic biological de-epoxidation is considered the ideal method of controlling these types of mycotoxins. In this study, we isolated a novel trichothecene mycotoxin-de-epoxidating bacterium, sp. PGC-3-9, from a consortium obtained from the soil of a wheat field known for the occurrence of frequent head blight epidemics under aerobic conditions. Along with MMYPF media, a combination of two antibiotics (sulfadiazine and trimethoprim) substantially increased the relative abundance of species from 1.55% (aerobic) to 29.11% (aerobic) and 28.63% (anaerobic). A single colony purified strain, PGC-3-9, was isolated and a 16S rRNA sequencing analysis determined that it was . The PGC-3-9 strain completely de-epoxidated HT-2, deoxynivalenol (DON), nivalenol and 15-acetyl deoxynivalenol, and efficiently eliminated DON in wheat grains under aerobic and anaerobic conditions. The strain PGC-3-9 exhibited high DON de-epoxidation activity at a wide range of pH (6-10) and temperature (15-50 °C) values under both conditions. This strain may be used for the development of detoxification agents in the agriculture and feed industries and the isolation of de-epoxidation enzymes.
Topics: Desulfitobacterium; Edible Grain; Food Microbiology; Fungi; Hydrogen-Ion Concentration; Inactivation, Metabolic; Oxygen; Soil Microbiology; Temperature; Trichothecenes; Triticum
PubMed: 32492959
DOI: 10.3390/toxins12060363 -
Microorganisms Mar 2020The relationship between predominant physiological types of prokaryotes in marine sediments and propionate degradation through sulfate reduction, fermentation, and...
The relationship between predominant physiological types of prokaryotes in marine sediments and propionate degradation through sulfate reduction, fermentation, and methanogenesis was studied in marine sediments. Propionate conversion was assessed in slurries containing sediment from three different biogeochemical zones of Aarhus Bay, Denmark. Sediment slurries were amended with 0, 3, or 20 mM sulfate and incubated at 25 °C and 10 °C for 514-571 days. Methanogenesis in the sulfate zone and sulfate reduction in the methane zone slurries was observed. Both processes occurred simultaneously in enrichments originating from samples along the whole sediment. Bacterial community analysis revealed the dominance of and members in sulfate-amended slurries incubated at 25°C and 10°C. belonging to the family dominated sulfate-free methanogenic slurries at 25°C, whereas bacteria related to were dominant at 10°C. Archaeal community analysis revealed the prevalence of different genera belonging to in slurries incubated at different temperatures and amended with different sulfate concentrations. were only detected in the absence of sulfate. In summary, Aarhus Bay sediment zones contain sulfate reducers, syntrophs, and methanogens interacting with each other in the conversion of propionate. Our results indicate that in Aarhus Bay sediments, degraded propionate in syntrophic association with methanogens
PubMed: 32168975
DOI: 10.3390/microorganisms8030394 -
The FEBS Journal Nov 2020Corrinoid-dependent enzyme systems rely on the super-reduced state of the protein-bound corrinoid cofactor to be functional, for example, in methyl transfer reactions....
Corrinoid-dependent enzyme systems rely on the super-reduced state of the protein-bound corrinoid cofactor to be functional, for example, in methyl transfer reactions. Due to the low redox potential of the [Co ]/[Co ] couple, autoxidation of the corrinoid cofactor occurs and leads to the formation of the inactive [Co ]-state. For the reactivation, which is an energy-demanding process, electrons have to be transferred from a physiological donor to the corrinoid cofactor by the help of a reductive activator protein. In this study, we identified reduced flavodoxin as electron donor for the ATP-dependent reduction of protein-bound corrinoid cofactors of bacterial O-demethylase enzyme systems. Reduced flavodoxin was generated enzymatically using pyruvate:ferredoxin/flavodoxin oxidoreductase rather than hydrogenase. Two of the four flavodoxins identified in Acetobacterium dehalogenans and Desulfitobacterium hafniense DCB-2 were functional in supplying electrons for corrinoid reduction. They exhibited a midpoint potential of about -400 mV (E , pH 7.5) for the semiquinone/hydroquinone transition. Reduced flavodoxin could be replaced by reduced clostridial ferredoxin. It was shown that the low-potential electrons of reduced flavodoxin are first transferred to the iron-sulfur cluster of the reductive activator and finally to the protein-bound corrinoid cofactor. This study further highlights the importance of reduced flavodoxin, which allows maintaining a variety of enzymatic reaction cycles by delivering low-potential electrons.
Topics: Acetobacterium; Adenosine Triphosphate; Bacterial Proteins; Corrinoids; Desulfitobacterium; Electrons; Flavodoxin; Hydroquinones; Oxidation-Reduction; Oxidoreductases; Spectrophotometry
PubMed: 32160390
DOI: 10.1111/febs.15290 -
Scientific Reports Feb 2020Impaired thermoregulation and lowered average daily gains (ADG) result when livestock graze toxic endophyte (Epichloë coenophialum)-infected tall fescue (E+) and are...
Impaired thermoregulation and lowered average daily gains (ADG) result when livestock graze toxic endophyte (Epichloë coenophialum)-infected tall fescue (E+) and are hallmark signs of fescue toxicosis (FT), a disease exacerbated by increased temperature and humidity (+temperature-humidity index; +THI). We previously reported FT is associated with metabolic and microbiota perturbations under thermoneutral conditions; here, we assessed the influence of E+ grazing and +THI on the microbiota:metabolome interactions. Using high-resolution metabolomics and 16S rRNA gene sequencing, plasma/urine metabolomes and the fecal microbiota of Angus steers grazing non-toxic or E+ tall fescue were evaluated in the context of +THI. E+ grazing affected the fecal microbiota profile; +THI conditions modulated the microbiota only in E+ steers. E+ also perturbed many metabolic pathways, namely amino acid and inflammation-related metabolism; +THI affected these pathways only in E+ steers. Integrative analyses revealed the E+ microbiota correlated and co-varied with the metabolomes in a THI-dependent manner. Operational taxonomic units in the families Peptococcaceae, Clostridiaceae, and Ruminococcaceae correlated with production parameters (e.g., ADG) and with multiple plasma/urine metabolic features, providing putative FT biomarkers and/or targets for the development of FT therapeutics. Overall, this study suggests that E+ grazing increases Angus steer susceptibility to +THI, and offers possible targets for FT interventions.
Topics: Animals; Cattle; Cattle Diseases; Environment; Epichloe; Feces; Gastrointestinal Microbiome; Herbivory; Lolium; Metabolome; Mycotoxicosis
PubMed: 32051515
DOI: 10.1038/s41598-020-59104-1 -
Frontiers in Microbiology 2019Altered gut microbiota has been identified during psychological stress, which causes severe health issues worldwide. The integrity of the intestinal barrier and...
Altered gut microbiota has been identified during psychological stress, which causes severe health issues worldwide. The integrity of the intestinal barrier and blood-brain barrier regulates the process of bacterial translocation and can supply the nervous system with real-time information about the environment. However, the association of gut microbiota with psychological stress remains to be fully interpreted. In this study, we established a psychological stress model using an improved communication box and compared the expression of tight junction proteins in multiple regions of the intestinal (duodenum, jejunum, ileum) and blood-brain (amygdala, hippocampus) barriers between model and control rats. We also conducted fecal microbiota analysis using 16S rRNA gene sequencing. Expression levels of the stress-related indicators adrenocorticotropic hormone, NR3C1,2, and norepinephrine were increased in the model group compared to control group. Psychological stress reduced brain and intestinal levels of tight junction proteins, including claudin5, occludin, α-actin, and ZO-1. Microbiota analysis revealed elevated microbial diversity and fecal proportions of , , and in the model group. Further analysis indicated a negative correlation of and , as well as a positive correlation of , , and , with claudin5, occludin, α-actin, and ZO-1. Our use of a rodent model to explore the association between compromised intestinal and blood-brain barriers and altered fecal microbiota under psychological stress improves our understanding of the gut-brain axis. Here, cues converge to control basic developmental processes in the intestine and brain such as barrier function. This study provides new directions for investigating the pathogenesis of emotional disorders and the formulation of clinical treatment.
PubMed: 32010111
DOI: 10.3389/fmicb.2019.03067 -
The ISME Journal Apr 2020Dichloromethane (DCM) is an anthropogenic pollutant with ozone destruction potential that is also formed naturally. Under anoxic conditions, fermentation of DCM to...
Dichloromethane (DCM) is an anthropogenic pollutant with ozone destruction potential that is also formed naturally. Under anoxic conditions, fermentation of DCM to acetate and formate has been reported in axenic culture Dehalobacterium formicoaceticum, and to acetate, H and CO in mixed culture RM, which harbors the DCM degrader 'Candidatus Dichloromethanomonas elyunquensis'. RM cultures produced 28.1 ± 2.3 μmol of acetate from 155.6 ± 9.3 μmol DCM, far less than the one third (i.e., about 51.9 µmol) predicted based on the assumed fermentation model, and observed in cultures of Dehalobacterium formicoaceticum. Temporal metabolite analyses using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy revealed that no C-labeled acetate was formed in C-DCM-grown RM cultures, indicating acetate was not a direct product of DCM metabolism. The data were reconciled with DCM mineralization and H consumption via CO reduction to acetate and methane by homoacetogenic and methanogenic partner populations, respectively. In contrast, Dehalobacterium formicoaceticum produced C-labeled acetate and formate from C-DCM, consistent with a fermentation pathway. Free energy change calculations predicted that organisms with the mineralization pathway are the dominant DCM consumers in environments with H <100 ppmv. These findings have implications for carbon and electron flow in environments where DCM is introduced through natural production processes or anthropogenic activities.
Topics: Acetates; Anaerobiosis; Bacteria, Anaerobic; Biodegradation, Environmental; Carbon; Carbon Dioxide; Euryarchaeota; Fermentation; Hydrogen; Methane; Methylene Chloride; Peptococcaceae
PubMed: 31907367
DOI: 10.1038/s41396-019-0579-5 -
PeerJ 2019Bacteria capable of dechlorinating the toxic environmental contaminant dichloromethane (DCM, CHCl) are of great interest for potential bioremediation applications. A...
Bacteria capable of dechlorinating the toxic environmental contaminant dichloromethane (DCM, CHCl) are of great interest for potential bioremediation applications. A novel, strictly anaerobic, DCM-fermenting bacterium, "DCMF", was enriched from organochlorine-contaminated groundwater near Botany Bay, Australia. The enrichment culture was maintained in minimal, mineral salt medium amended with dichloromethane as the sole energy source. PacBio whole genome SMRT sequencing of DCMF allowed , gap-free assembly despite the presence of cohabiting organisms in the culture. Illumina sequencing reads were utilised to correct minor indels. The single, circularised 6.44 Mb chromosome was annotated with the IMG pipeline and contains 5,773 predicted protein-coding genes. Based on 16S rRNA gene and predicted proteome phylogeny, the organism appears to be a novel member of the family. The DCMF genome is large in comparison to known DCM-fermenting bacteria. It includes an abundance of methyltransferases, which may provide clues to the basis of its DCM metabolism, as well as potential to metabolise additional methylated substrates such as quaternary amines. Full annotation has been provided in a custom genome browser and search tool, in addition to multiple sequence alignments and phylogenetic trees for every predicted protein, http://www.slimsuite.unsw.edu.au/research/dcmf/.
PubMed: 31592187
DOI: 10.7717/peerj.7775