scholarly journals Anaerobic Degradation of Non-Methane Alkanes by “Candidatus Methanoliparia” in Hydrocarbon Seeps of the Gulf of Mexico

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Rafael Laso-Pérez ◽  
Cedric Hahn ◽  
Daan M. van Vliet ◽  
Halina E. Tegetmeyer ◽  
Florence Schubotz ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Anaerobic Degradation ◽  
Single Cells ◽  
Short Chain ◽  
Alkane Degradation ◽  
Coenzyme M ◽  
Oil Droplets ◽  
Marine Habitats ◽  
Methyl Coenzyme M Reductase ◽  
Long Chain

ABSTRACT Crude oil and gases in the seabed provide an important energy source for subsurface microorganisms. We investigated the role of archaea in the anaerobic degradation of non-methane alkanes in deep-sea oil seeps from the Gulf of Mexico. We identified microscopically the ethane and short-chain alkane oxidizers “Candidatus Argoarchaeum” and “Candidatus Syntrophoarchaeum” forming consortia with bacteria. Moreover, we found that the sediments contain large numbers of cells from the archaeal clade “Candidatus Methanoliparia,” which was previously proposed to perform methanogenic alkane degradation. “Ca. Methanoliparia” occurred abundantly as single cells attached to oil droplets in sediments without apparent bacterial or archaeal partners. Metagenome-assembled genomes of “Ca. Methanoliparia” encode a complete methanogenesis pathway including a canonical methyl-coenzyme M reductase (MCR) but also a highly divergent MCR related to those of alkane-degrading archaea and pathways for the oxidation of long-chain alkyl units. Its metabolic genomic potential and its global detection in hydrocarbon reservoirs suggest that “Ca. Methanoliparia” is an important methanogenic alkane degrader in subsurface environments, producing methane by alkane disproportionation as a single organism. IMPORTANCE Oil-rich sediments from the Gulf of Mexico were found to contain diverse alkane-degrading groups of archaea. The symbiotic, consortium-forming “Candidatus Argoarchaeum” and “Candidatus Syntrophoarchaeum” are likely responsible for the degradation of ethane and short-chain alkanes, with the help of sulfate-reducing bacteria. “Ca. Methanoliparia” occurs as single cells associated with oil droplets. These archaea encode two phylogenetically different methyl-coenzyme M reductases that may allow this organism to thrive as a methanogen on a substrate of long-chain alkanes. Based on a library survey, we show that “Ca. Methanoliparia” is frequently detected in oil reservoirs and may be a key agent in the transformation of long-chain alkanes to methane. Our findings provide evidence for the important and diverse roles of archaea in alkane-rich marine habitats and support the notion of a significant functional versatility of the methyl coenzyme M reductase.

scholarly journals “Candidatus Ethanoperedens,” a Thermophilic Genus of Archaea Mediating the Anaerobic Oxidation of Ethane

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Cedric Jasper Hahn ◽  
Rafael Laso-Pérez ◽  
Francesca Vulcano ◽  
Konstantinos-Marios Vaziourakis ◽  
Runar Stokke ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Gulf Of California ◽  
Molecular Mechanisms ◽  
Stable Isotope Probing ◽  
Microbial Consortia ◽  
Cold Seeps ◽  
Ethane Oxidation ◽  
Alkane Degradation ◽  
Coenzyme M ◽  
Methyl Coenzyme M Reductase

ABSTRACT Cold seeps and hydrothermal vents deliver large amounts of methane and other gaseous alkanes into marine surface sediments. Consortia of archaea and partner bacteria thrive on the oxidation of these alkanes and its coupling to sulfate reduction. The inherently slow growth of the involved organisms and the lack of pure cultures have impeded the understanding of the molecular mechanisms of archaeal alkane degradation. Here, using hydrothermal sediments of the Guaymas Basin (Gulf of California) and ethane as the substrate, we cultured microbial consortia of a novel anaerobic ethane oxidizer, “Candidatus Ethanoperedens thermophilum” (GoM-Arc1 clade), and its partner bacterium “Candidatus Desulfofervidus auxilii,” previously known from methane-oxidizing consortia. The sulfate reduction activity of the culture doubled within one week, indicating a much faster growth than in any other alkane-oxidizing archaea described before. The dominance of a single archaeal phylotype in this culture allowed retrieval of a closed genome of “Ca. Ethanoperedens,” a sister genus of the recently reported ethane oxidizer “Candidatus Argoarchaeum.” The metagenome-assembled genome of “Ca. Ethanoperedens” encoded a complete methanogenesis pathway including a methyl-coenzyme M reductase (MCR) that is highly divergent from those of methanogens and methanotrophs. Combined substrate and metabolite analysis showed ethane as the sole growth substrate and production of ethyl-coenzyme M as the activation product. Stable isotope probing demonstrated that the enzymatic mechanism of ethane oxidation in “Ca. Ethanoperedens” is fully reversible; thus, its enzymatic machinery has potential for the biotechnological development of microbial ethane production from carbon dioxide. IMPORTANCE In the seabed, gaseous alkanes are oxidized by syntrophic microbial consortia that thereby reduce fluxes of these compounds into the water column. Because of the immense quantities of seabed alkane fluxes, these consortia are key catalysts of the global carbon cycle. Due to their obligate syntrophic lifestyle, the physiology of alkane-degrading archaea remains poorly understood. We have now cultivated a thermophilic, relatively fast-growing ethane oxidizer in partnership with a sulfate-reducing bacterium known to aid in methane oxidation and have retrieved the first complete genome of a short-chain alkane-degrading archaeon. This will greatly enhance the understanding of nonmethane alkane activation by noncanonical methyl-coenzyme M reductase enzymes and provide insights into additional metabolic steps and the mechanisms underlying syntrophic partnerships. Ultimately, this knowledge could lead to the biotechnological development of alkanogenic microorganisms to support the carbon neutrality of industrial processes.

scholarly journals Functional and Genomic Characterization of a Pseudomonas aeruginosa Strain Isolated From the Southwestern Gulf of Mexico Reveals an Enhanced Adaptation for Long-Chain Alkane Degradation

2019 ◽  
Vol 6 ◽  
Author(s):  
Luis Felipe Muriel-Millán ◽  
José Luis Rodríguez-Mejía ◽  
Elizabeth Ernestina Godoy-Lozano ◽  
Nancy Rivera-Gómez ◽  
Rosa-María Gutierrez-Rios ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gulf Of Mexico ◽  
Alkane Degradation ◽  
Genomic Characterization ◽  
Long Chain

scholarly journals The absorption of stearic acid from triacylglycerols: an inquiry and analysis

2000 ◽  
Vol 13 (2) ◽  
pp. 185-214 ◽  
Author(s):  
Geoffrey Livesey
Keyword(s):  
Fatty Acids ◽  
Body Weight ◽  
Melting Point ◽  
Cocoa Butter ◽  
Stearic Acid ◽  
Short Chain ◽  
Apparent Digestibility ◽  
Long Chain Fatty Acids ◽  
Long Chain ◽  
Chain Fatty Acids

AbstractAlthough stearic acid is a saturated fatty acid, its influence on plasma cholesterol acid other health variables is neutral; possibly owing in part to poor absorption. Reduced absorption of stearic acid from particular triacylglycerols, cocoa butter and novel fats formulated with short- and long-chain acid triacylglycerol molecules (Salatrims) has been attributed to high intakes. However, the circumstances and causes of poor stearic acid digestion from triacylglycerols are unclear; published data were therefore collected and analysed, with emphasis on human studies. Of twenty-eight studies conducted in adults, most are in men (>90%). The assertion that reduced absorption is due to a high intake of stearoyl groups is not supported: dietary intakes of stearoyl of 0·05–0·65 g stearic acid equivalent/kg body weight (cf typical intake of 0·2 g stearic acid equivalent/kg body weight in the Western diet) indicate that the ‘true’ digestibility of stearoyl is 0·98 (SE 0·01) g/g, with apparent digestibility less than this value at low intakes owing to endogenous stearic acid excretion and to inter-publication variation of unidentified cause. The neutral health impact of stearic acid must be due to factors other than availability. Exceptions include cocoa butter, Salatrims and tristearin, for which digestibility is an additional factor. The efficiency with which human subjects digest stearoyl from cocoa butter still remains uncertain, while the digestion of total long-chain fat from this source is 0·89–0·95 g/g, high in comparison with 0·33 g/g for Salatrim 23CA and 0·15 g/g for tristearin in their prepared states. Salatrims contain the highest proportion of long-chain fatty acids that are stearic acid-rich other than tristearin, which is the main component of fully-hydrogenated soyabean and rapeseed oil. Analysis shows that apparent digestibility of stearic acid is associated with stearoyl density within the triacylglycerol molecule and that, in Salatrims, the occurrence of short-chain fatty acids in place of long-chain fatty acids increases this density. Soap formation appears not to be a major factor in the reduced digestion of stearic acid from tristearin under regular dietary circumstances, but both microcrystallinity and reduced digestibility of tri-, di- and monostearoylglycerols appears to be important. Solubilisation of high-melting-point tristearin in low-melting-point oils improves the digestibility of its stearic acid, particularly when emulsified or liquidized at above melting point. However, without such artificial aids, the digestive tracts of the rat, dog and man have a low capacity for emulsifying and digesting stearic acid from tristearin. Reduced digestibility of stearic acid from Salatrim 23CA also appears to be attributable to reduced digestibility of di- and monostearoylglycerols and is particularly due to remnants with the 1- or 3-stearoylglycerol intact after initial hydrolytic cleavage. Short-chain organic acid in Salatrim 23CA, which is readily hydrolysed, leaves such remnants. Unlike tristearin, Salatrim 23CA melts at body temperature and mixing it with low-melting-point oils is not expected to cause further disruption of microcrystalline structures to aid digestibility of its stearoyl groups. The low digestibility of stearoyl in Salatrim 23CA, together with the occurrence of short-chain organic acids in this product, account for its relatively low nutritional energy value (about 20 kJ (5 kcal)/g) compared with traditional fats (37 kJ (9 kcal)/g) and low fat value (<20:37 kJ/kJ; <5:9 kcal/kcal) relative to traditional fats. In part these differences are because of minor effects of Salatrim 23CA on the excretion of other fat and protein, due to the bulking properties of this poorly-digestible fat.

Jumping on the Omega-3 Bandwagon: Distinguishing the Role of Long-Chain and Short-Chain Omega-3 Fatty Acids

2012 ◽  
Vol 52 (9) ◽  
pp. 795-803 ◽  
Author(s):  
Giovanni M. Turchini ◽  
Peter D. Nichols ◽  
Colin Barrow ◽  
Andrew J. Sinclair
Keyword(s):  
Fatty Acids ◽  
Short Chain ◽  
Omega 3 Fatty Acids ◽  
Omega 3 ◽  
Long Chain

scholarly journals Expression, Purification, and Characterization of (R)-Sulfolactate Dehydrogenase (ComC) from the Rumen MethanogenMethanobrevibacter milleraeSM9

Archaea ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-6
Author(s):  
Yanli Zhang ◽  
Linley R. Schofield ◽  
Carrie Sang ◽  
Debjit Dey ◽  
Ron S. Ronimus
Keyword(s):  
Biosynthetic Pathway ◽  
Critical Role ◽  
Reduction Reaction ◽  
Coenzyme M ◽  
Purification And Characterization ◽  
The Third ◽  
Optimal Activity ◽  
Methyl Coenzyme M Reductase

(R)-Sulfolactate dehydrogenase (EC 1.1.1.337), termed ComC, is a member of an NADH/NADPH-dependent oxidoreductase family of enzymes that catalyze the interconversion of 2-hydroxyacids into their corresponding 2-oxoacids. The ComC reaction is reversible and in the biosynthetic direction causes the conversion of (R)-sulfolactate to sulfopyruvate in the production of coenzyme M (2-mercaptoethanesulfonic acid). Coenzyme M is an essential cofactor required for the production of methane by the methyl-coenzyme M reductase complex. ComC catalyzes the third step in the first established biosynthetic pathway of coenzyme M and is also involved in methanopterin biosynthesis. In this study, ComC fromMethanobrevibacter milleraeSM9 was cloned and expressed inEscherichia coliand biochemically characterized. Sulfopyruvate was the preferred substrate using the reduction reaction, with 31% activity seen for oxaloacetate and 0.2% seen forα-ketoglutarate. Optimal activity was observed at pH 6.5. The apparentKMfor coenzyme (NADH) was 55.1 μM, and for sulfopyruvate, it was 196 μM (for sulfopyruvate theVmaxwas 93.9 μmol min−1 mg−1andkcatwas 62.8 s−1). The critical role of ComC in two separate cofactor pathways makes this enzyme a potential means of developing methanogen-specific inhibitors for controlling ruminant methane emissions which are increasingly being recognized as contributing to climate change.

scholarly journals A methylotrophic origin of methanogenesis and early divergence of anaerobic multicarbon alkane metabolism

2021 ◽  
Vol 7 (27) ◽  
pp. eabj1453
Author(s):  
Yinzhao Wang ◽  
Gunter Wegener ◽  
Tom A. Williams ◽  
Ruize Xie ◽  
Jialin Hou ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Energy Conservation ◽  
Life Forms ◽  
Short Chain ◽  
Present Evidence ◽  
Origin And Evolution ◽  
Ancestral Form ◽  
Climate Stability ◽  
Long Chain

Methanogens are considered as one of the earliest life forms on Earth, and together with anaerobic methane-oxidizing archaea, they have crucial effects on climate stability. However, the origin and evolution of anaerobic alkane metabolism in the domain Archaea remain controversial. Here, we present evidence that methylotrophic methanogenesis was the ancestral form of this metabolism. Carbon dioxide–reducing methanogenesis developed later through the evolution of tetrahydromethanopterin S-methyltransferase, which linked methanogenesis to the Wood-Ljungdahl pathway for energy conservation. Anaerobic multicarbon alkane metabolisms in Archaea also originated early, with genes coding for the activation of short-chain or even long-chain alkanes likely evolving from an ethane-metabolizing ancestor. These genes were likely horizontally transferred to multiple archaeal clades including Candidatus (Ca.) Bathyarchaeia, Ca. Lokiarchaeia, Ca. Hadarchaeia, and the methanogenic Ca. Methanoliparia.

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