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Gut Microbes 2021Several studies reported a potential role of methane producing archaea in the pathophysiology of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We... (Meta-Analysis)
Meta-Analysis
Several studies reported a potential role of methane producing archaea in the pathophysiology of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We conducted a systematic review and meta-analysis to assess the prevalence of methane positive small intestinal bacterial overgrowth (SIBO) in IBS and IBD compared with controls. MEDLINE (PubMed) and Embase electronic databases were searched from inception until March 2021 for case-control and prevalence studies reporting SIBO in IBS and IBD. We extracted data from published studies and calculated pooled prevalence of SIBO in IBS or IBD, odds ratios (OR), and 95% CIs, utilizing a random effects model. The final dataset included 17 independent studies assessing the prevalence of methane positive SIBO in 1,653 IBS-patients and 713 controls, and 7 studies assessing the prevalence of methane positive SIBO in 626 IBD-patients and 497 controls, all utilizing breath test for SIBO diagnosis. Prevalence of methane positive SIBO in IBS and IBD was 25.0% (95% CI 18.8-32.4) and 5.6% (95% CI 2.6-11.8), respectively. Methane positive SIBO in IBS was not increased compared to controls (OR = 1.2, 95% CI 0.8-1.7, = .37) but was significantly more prevalent in IBS-C as compared to IBS-D (OR = 3.1, 95% CI 1.7-5.6, = .0001). The prevalence of methane-positive SIBO in patients with IBD was 3-fold lower at 7.4% (95% CI 5.4-9.8) compared to 23.5% (95% CI 19.8-27.5) in controls. The prevalence of methane positive SIBO was significantly lower in Crohn's disease as compared to ulcerative colitis, (5.3%, 95% CI 3.0-8.5 vs. 20.2%, 95% CI 12.8-29.4). This systematic review and meta-analysis suggests methane positivity on breath testing is positively associated with IBS-C and inversely with IBD. However, the quality of evidence is low largely due to clinical heterogeneity of the studies. Thus, causality is uncertain and further studies are required.
Topics: Bacteria; Breath Tests; Case-Control Studies; Female; Humans; Inflammatory Bowel Diseases; Intestine, Small; Irritable Bowel Syndrome; Male; Methane
PubMed: 34190027
DOI: 10.1080/19490976.2021.1933313 -
Molecules (Basel, Switzerland) Nov 2023(indolyl)methanes (BIMs) are a class of compounds that have been recognized as an important core in the design of drugs with important pharmacological properties, such...
(indolyl)methanes (BIMs) are a class of compounds that have been recognized as an important core in the design of drugs with important pharmacological properties, such as promising anticancer and antiparasitic activities. Here, we explored the biological activity of the BIM core functionalized with different (hetero)aromatic moieties. We synthesized substituted BIM derivatives with triphenylamine, -dimethyl-1-naphthylamine and 8-hydroxylquinolyl groups, studied their photophysical properties and evaluated their in vitro antiproliferative and antiparasitic activities. The triphenylamine BIM derivative displayed an IC of 3.21, 3.30 and 3.93 μM against , and HT-29 cancer cell line, respectively. The selectivity index demonstrated that compound was up to eight-fold more active against the parasites and HT-29 than against the healthy cell line MRC-5. Fluorescence microscopy studies with MRC-5 cells and parasites incubated with derivative indicate that the compound seems to accumulate in the cell's mitochondria and in the parasite's nucleus. In conclusion, the BIM scaffold functionalized with the triphenylamine moiety proved to be the most promising antiparasitic and anticancer agent of this series.
Topics: Humans; Antiparasitic Agents; Methane; Trypanosoma brucei brucei; Antineoplastic Agents; Neoplasms; Structure-Activity Relationship
PubMed: 38067459
DOI: 10.3390/molecules28237728 -
Journal of Dairy Science Sep 2022The effects of different ruminal protozoa (RP) on CH emissions from ruminants were evaluated in a meta-analysis, using 64 publications reporting data from 79 in vivo... (Meta-Analysis)
Meta-Analysis
The effects of different ruminal protozoa (RP) on CH emissions from ruminants were evaluated in a meta-analysis, using 64 publications reporting data from 79 in vivo experiments. Experiments included in the database reported CH emissions (g/d) and total RP (TRP, log cells/mL) from the same group of animals. The relationship between CH emissions and RP (TRP, entodiniomorphids, and isotrichids), and TRP-, entodiniomorphid-, and isotrichid-based CH emission prediction models, were evaluated as mixed models with experiment as a random effect and weighted by the reciprocal of the standard error of the mean and centered around one. Positive associations existed between TRP and isotrichids with CH emissions but not between entodiniomorphids and CH emissions. A reduction in CH emissions was observed, averaging 7.96 and 4.25 g/d, per log unit reduction in TRP and isotrichid concentrations, respectively. Total RP and isotrichids were important variables in predicting CH emissions from ruminants. Isotrichid CH prediction model was more robust than the TRP, evidenciated by lower predicted sigma hat study (%), and error (%), and with higher concordance correlation coefficient. Both TRP and isotrichid models can accurately predict CH emissions across different ruminant types, as shown by the low square root of the mean square prediction error, with 6.59 and 4.08% of the mean of root of the mean square prediction error in the TRP and isotrichid models, respectively. Our results confirm that isotrichids are more important than entodiniomorphids in methanogenesis. Distinguishing these 2 populations yielded a more robust CH prediction model than combining them as total protozoa.
Topics: Animals; Diet; Methane; Rumen; Ruminants
PubMed: 35931473
DOI: 10.3168/jds.2021-21139 -
Proceedings of the National Academy of... Apr 2022Methane has been proposed as an exoplanet biosignature. Imminent observations with the James Webb Space Telescope may enable methane detections on potentially habitable...
Methane has been proposed as an exoplanet biosignature. Imminent observations with the James Webb Space Telescope may enable methane detections on potentially habitable exoplanets, so it is essential to assess in what planetary contexts methane is a compelling biosignature. Methane’s short photochemical lifetime in terrestrial planet atmospheres implies that abundant methane requires large replenishment fluxes. While methane can be produced by a variety of abiotic mechanisms such as outgassing, serpentinizing reactions, and impacts, we argue that—in contrast to an Earth-like biosphere—known abiotic processes cannot easily generate atmospheres rich in CH4 and CO2 with limited CO due to the strong redox disequilibrium between CH4 and CO2. Methane is thus more likely to be biogenic for planets with 1) a terrestrial bulk density, high mean-molecular-weight and anoxic atmosphere, and an old host star; 2) an abundance of CH4 that implies surface fluxes exceeding what could be supplied by abiotic processes; and 3) atmospheric CO2 with comparatively little CO.
Topics: Atmosphere; Earth, Planet; Exobiology; Extraterrestrial Environment; Methane; Planets
PubMed: 35353627
DOI: 10.1073/pnas.2117933119 -
ACS Synthetic Biology May 2024Ruminant livestock produce around 24% of global anthropogenic methane emissions. Methanogenesis in the animal rumen is significantly inhibited by bromoform, which is...
Ruminant livestock produce around 24% of global anthropogenic methane emissions. Methanogenesis in the animal rumen is significantly inhibited by bromoform, which is abundant in seaweeds of the genus . This has prompted the development of livestock feed additives based on to mitigate methane emissions, although this approach alone is unlikely to satisfy global demand. Here we engineer a non-native biosynthesis pathway to produce bromoform in vivo with yeast as an alternative biological source that may enable sustainable, scalable production of bromoform by fermentation. β-dicarbonyl compounds with low pa values were identified as essential substrates for bromoform production and enabled bromoform synthesis in engineered expressing a vanadate-dependent haloperoxidase gene. In addition to providing a potential route to the sustainable biological production of bromoform at scale, this work advances the development of novel microbial biosynthetic pathways for halogenation.
Topics: Saccharomyces cerevisiae; Metabolic Engineering; Biosynthetic Pathways; Animals; Fermentation; Methane; Seaweed; Halogenation
PubMed: 38525720
DOI: 10.1021/acssynbio.4c00005 -
Journal of Bacteriology Aug 2023Methanogenic archaea are the only organisms that produce CH as part of their energy-generating metabolism. They are ubiquitous in oxidant-depleted, anoxic environments... (Review)
Review
Methanogenic archaea are the only organisms that produce CH as part of their energy-generating metabolism. They are ubiquitous in oxidant-depleted, anoxic environments such as aquatic sediments, anaerobic digesters, inundated agricultural fields, the rumen of cattle, and the hindgut of termites, where they catalyze the terminal reactions in the degradation of organic matter. Methanogenesis is the only metabolism that is restricted to members of the domain . Here, we discuss the importance of model organisms in the history of methanogen research, including their role in the discovery of the archaea and in the biochemical and genetic characterization of methanogenesis. We also discuss outstanding questions in the field and newly emerging model systems that will expand our understanding of this uniquely archaeal metabolism.
Topics: Animals; Cattle; Archaea; Methane; Energy Metabolism
PubMed: 37458589
DOI: 10.1128/jb.00115-23 -
Environmental Science & Technology Feb 2023Success in reducing oil and gas sector methane emissions is contingent on understanding the sources driving emissions, associated options for mitigation, and the...
Success in reducing oil and gas sector methane emissions is contingent on understanding the sources driving emissions, associated options for mitigation, and the effectiveness of regulations in achieving intended outcomes. This study combines high-resolution, high-sensitivity aerial survey data with subsequent on-site investigations of detected sources to examine these points. Measurements were performed in British Columbia, Canada, an active oil- and gas-producing province with modern methane regulations featuring mandatory three times per year leak detection and repair (LDAR) surveys at most facilities. Derived emission factors enabled by source attribution show that significant methane emissions persist under this regulatory framework, dominated by (i) combustion slip (compressor exhaust and also catalytic heaters, which are not covered in current regulations), (ii) intentional venting (uncontrolled tanks, vent stacks or intentionally unlit flares, and uncontrolled compressors), and (iii) unintentional venting (controlled tanks, unintentionally unlit/blown out flares, and abnormally operating pneumatics). Although the detailed analysis shows mitigation options exist for all sources, the importance of combustion slip and the persistently large methane contributions from controlled tanks and unlit flares demonstrate the limits of current LDAR programs and the critical need for additional monitoring and verification if regulations are to have the intended impacts, and reduction targets of 75% and greater are to be met.
Topics: Methane; Air Pollutants; Vehicle Emissions; British Columbia; Surveys and Questionnaires; Natural Gas
PubMed: 36716186
DOI: 10.1021/acs.est.2c07318 -
Journal of Environmental Management Nov 2023Achieving the ambitious Global Methane Pledge announced in the Glasgow Climate Pact requires collaborative efforts from both the signatory countries and China which...
Achieving the ambitious Global Methane Pledge announced in the Glasgow Climate Pact requires collaborative efforts from both the signatory countries and China which serves as the world's largest emitter. Considering the heterogeneity of economic structures within China and the relocation of emissions between regions via the global economic network, it is vital to investigate how China's methane emissions at the subnational level are linked to global final consumption. In this paper, we mapped global methane footprint in China from 2007 to2015 at the subnational level, by nesting China's interprovincial input-output tables into global multiregional input-output accounts and upscaling grid-level methane emission data of the Edgar database to the provincial level. Our results suggested that global methane footprint in China shifted westward, and the United States, European Union, Japan, and Hong Kong were the main drivers of China's local methane emissions. By illustrating the international and interprovincial trade flows of methane emissions, this study demonstrated that southeast coastal provinces were the hotspots for global methane footprint while middle inland provinces were the emission hotspots for China's domestic demands. We also showed how China's methane emissions were distributed through the nested global economic network to different economic agents. Moreover, emission trends of key exporting sectors for China's eight economic zones were detailed discussed. The outcome of this study may be fully supportive for identifying the heterogeneous effects of global methane footprint in China and implicative for interprovincial and international collaborations towards methane emission mitigation.
Topics: Methane; China; Hong Kong; Climate; Japan; Carbon Dioxide
PubMed: 37421727
DOI: 10.1016/j.jenvman.2023.118479 -
Marine Pollution Bulletin Jan 2022Biologically productive regions such as estuaries and coastal areas, even though they only cover a small percentage of the world's oceans, contribute significantly to... (Review)
Review
Biologically productive regions such as estuaries and coastal areas, even though they only cover a small percentage of the world's oceans, contribute significantly to methane and nitrous oxide emissions. This paper synthesises greenhouse gas data measured in UK estuary studies, highlighting that urban wastewater loading is significantly correlated with both methane (P < 0.001) and nitrous oxide (P < 0.005) concentrations. It demonstrates that specific estuary typologies render them more sensitive to anthropogenic influences on greenhouse gas production, particularly estuaries that experience low oxygen levels due to reduced mixing and stratification or high sediment oxygen demand. Significantly, we find that estuaries with high urban wastewater loading may be hidden sources of greenhouse gases globally. Synthesising available information, a conceptual model for greenhouse gas concentrations in estuaries with different morphologies and mixing regimes is presented. Applications of this model should help identification of estuaries susceptible to anthropogenic impacts and potential hotspots for greenhouse gas emissions.
Topics: Anthropogenic Effects; Estuaries; Greenhouse Gases; Methane; Nitrous Oxide
PubMed: 35090288
DOI: 10.1016/j.marpolbul.2021.113240 -
Environmental Science & Technology Jan 2021Unburned methane entrained in exhaust from natural gas-fired compressor engines ("combustion slip") can account for a substantial portion of station-level methane...
Unburned methane entrained in exhaust from natural gas-fired compressor engines ("combustion slip") can account for a substantial portion of station-level methane emissions. A novel in-stack, tracer gas method was coupled with Fourier transform infrared (FTIR) species measurements to quantify combustion slip from natural gas compressor engines at 67 gathering and boosting stations owned or managed by nine "study partner" operators in 11 U.S. states. The mean methane emission rate from 63 four-stroke, lean-burn (4SLB) compressor engines was 5.62 kg/h (95% CI = 5.15-6.17 kg/h) and ranged from 0.3 to 12.6 kg/h. The mean methane emission rate from 39 four-stroke, rich-burn (4SRB) compressor engines was 0.40 kg/h (95% CI = 0.37-0.42 kg/h) and ranged from 0.01 to 4.5 kg/h. Study results for 4SLB engines were lower than both the U.S. EPA compilation of air pollutant emission factors (AP-42) and Inventory of U.S. Greenhouse Gas Emissions and Sinks (GHGI) by 8 and 9%, respectively. Study results for 4SRB engines were 43% of the AP-42 emission factor and 8% of the GHGI emission factor, the latter of which does not distinguish between engine types. Total annual combustion slip from the U.S. natural gas gathering and boosting sector was modeled using measured emission rates and compressor unit counts from the U.S. EPA Greenhouse Gas Reporting Program. Modeled results [328 Gg/y (95% CI = 235-436 Gg/y) of unburned methane] would account for 24% (95% CI = 17-31%) of the 1391 Gg of methane emissions for "Gathering and Boosting Stations", or 6% of the net emissions for "Natural Gas Systems" (5598 Gg) as reported in the 2020 U.S. EPA GHGI. Gathering and boosting combustion slip emissions reported in the 2020 GHGI (374 Gg) fall within the uncertainty of this model.
Topics: Air Pollutants; Greenhouse Gases; Methane; Natural Gas; United States; Vehicle Emissions
PubMed: 33410668
DOI: 10.1021/acs.est.0c05492