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At least 19 recordsLinked to original sources
PubMed1978

Thermophilic methanogenesis in a hot-spring algal-bacterial mat (71 to 30 degrees C).

Algal-bacterial mats which grow in the effluent channels of alkaline hot springs provided an environment suitable for studying natural thermophilic methane producing bacteria. Methane was rapidly produced in cores taken from the meat and appeared to be an end product of decomposition of the algal-bacterial organic matter. Formaldehyde prevented production of methane. Initial methanogenic rate was lower and methanogenesis became exponential when samples were permitted to cool before laboratory incubation. Methanogenesis occurred and methanogenic bacteria were present over a range of 68 to 30 degrees C, with optimum methanogenesis near 45 degrees C. The temperature distribution of methanogenesis in the mat is discussed relative to published results on standing crop, primary production, and decomposition in the thermal gradient. The depth distribution of methanogenesis was similar to that of freshwater sediments, with a zone of intense methanogenesis near the mat surface. Methanogenesis in deeper mat layers was very low or undetectable despite large numbers of viable methanogenic bacteria and could not be stimulated by addition of anoxic source water, sulfide, or a macronutrient solution.

Anaerobiosis↗
PubMed2026

Integrative analysis of rumen microbiota activity and host metabolism following methanogenesis inhibition in dairy cattle.

Enteric methane emission from dairy cattle is an environmental challenge. The most efficient mitigation strategies nowadays include the use of methanogenesis inhibitors that specifically target the rumen methanogens. Specific inhibitors, such as 3-nitrooxypropanol (3-NOP), reduce methane emissions without negative effects on the products of fermentation that serve as energy metabolites for the host. However, the concomitant effects of methanogenesis inhibition on rumen microbiota and host metabolism are poorly characterized. Thus, the objective of this study was to explore the association between rumen microbiota and host metabolism when methanogenesis is inhibited. Thirteen dairy cows were used as controls, and 12 were supplemented with 3-NOP for 6 weeks. Rumen microbiota composition and activity were characterized using metagenomics and metatranscriptomics. The host metabolism was assessed in a previous publication by a metabolomic analysis of the plasma. Microbiota data were used as explanatory variables of the metabolome data in a multiblock sparse partial least squares analysis. Overall, the association between rumen microbiota and host metabolism was moderate. Notwithstanding this, a few downregulated transcripts related to glycolysis, hydrogen transfer, and protein synthesis, together with a decrease in the proportion of taxa of the Oscillospirales order, showed a correlation with host one-carbon metabolites (|r| > 0.6). These associations raised novel hypotheses that remain to be elucidated, especially with regard to the effects of dihydrogen on the accumulation of microbial glycolysis and methanogenesis metabolite intermediates.IMPORTANCEDairy cattle produce a substantial amount of methane, a potent greenhouse gas. Several strategies have been designed to reduce methane production by targeting the rumen microbiota. One such strategy specifically inhibits methanogens with a molecule called 3-nitrooxypropanol. This study uses an integrative data analysis approach, combining rumen microbiota and host metabolome information, to explore the consequences of inhibiting methanogenesis on the holobiont. This provides additional holistic insight into the effect of methane mitigation strategies on dairy cattle.

Animals↗
PubMed1976

Temperature limitation of methanogenesis in aquatic sediments.

Microbial methanogenesis was examined in sediments collected from Lake Mendota, Wisconsin, at water depths of 5, 10, and 18 m. The rate of sediment methanogenesis was shown to vary with respect to sediment site and depth, sampling date, in situ temperature, and number of methanogens. Increased numbers of methanogenic bacteria and rates of methanogenesis correlated with increased sediment temperature during seasonal change. The greatest methanogenic activity was observed for 18-m sediments throughout the sampling year. As compared with shallower sediments, 18-m sediment was removed from oxygenation effects and contained higher amounts of ammonia, carbonate, and methanogenic bacteria, and the population density of methanogens fluctuated less during seasonal change. Rates of methanogenesis in 18-m sediment cores decreased with increasing sediment depth. The optimum temperature, 35 to 42 C, for sediment methanogenesis was considerably higher than the maximum observed in situ temperature of 23 C. The conversion of H2 and [14C]carbonate to [14C]methane displayed the same temperature optimum when these substrates were added to sediments. The predominant methanogenic population had simple nutritional requirements and were metabolically active at 4 to 45 C. Hydrogen oxidizers were the major nutritional type of sediment methanogens; formate and methanol fermentors were present, but acetate fermentors were not observed. Methanobacterium species were most abundant in sediments although Methanosarcina, Methanococcus, and Methanospirillum species were observed in enrichment cultures. A chemolithotropic species of Methanosarcina and Methanobacterium was isolated in pure culture that displayed temperature optima above 30 C and had simple nutritional requirements.

Cell Count↗
PubMed1978

Growth and methanogenesis by Methanosarcina strain 227 on acetate and methanol.

Methanosarcina strain 227 exhibited exponential growth on sodium acetate in the absence of added H(2). Under these conditions, rates of methanogenesis were limited by concentrations of acetate below 0.05 M. One mole of methane was formed per mole of acetate consumed. Additional evidence from radioactive labeling studies indicated that sufficient energy for growth was obtained by the decarboxylation of acetate. Diauxic growth and sequential methanogenesis from methanol followed by acetate occurred in the presence of mixtures of methanol and acetate. Detailed studies showed that methanol-grown cells did not metabolize acetate in the presence of methanol, although acetate-grown cells did metabolize methanol and acetate simultaneously before shifting to methanol. Acetate catabolism appeared to be regulated in response to the presence of better metabolizable substrates such as methanol or H(2)-CO(2) by a mechanism resembling catabolite repression. Inhibition of methanogenesis from acetate by 2-bromoethanesulfonate, an analog of coenzyme M, was reversed by addition of coenzyme M. Labeling studies also showed that methanol may lie on the acetate pathway. These results suggested that methanogenesis from acetate, methanol, and H(2)-CO(2) may have some steps in common, as originally proposed by Barker. Studies with various inhibitors, together with molar growth yield data, suggest a role for electron transport mechanisms in energy metabolism during methanogenesis from methanol, acetate, and H(2)-CO(2).

Acetates↗
PubMed1979

Microbial methanogenesis and acetate metabolism in a meromictic lake.

Methanogenesis and the anaerobic metabolism of acetate were examined in the sediment and water column of Knaack Lake, a small biogenic meromictic lake located in central Wisconsin. The lake was sharply stratified during the summer and was anaerobic below a depth of 3 m. Large concentrations (4,000 mumol/liter) of dissolved methane were detected in the bottom waters. A methane concentration maximum occurred at 4 m above the sediment. The production of (14)CH(4) from (14)C-labeled HCOOH, HCO(3) (-), and CH(3)OH and [2-(14)C]acetate demonstrated microbial methanogenesis in the water column of the lake. The maximum rate of methanogenesis calculated from reduction of H(14)CO(3) (-) by endogenous electron donors in the surface sediment (depth, 22 m) was 7.6 nmol/h per 10 ml and in the water column (depth, 21 m) was 0.6 nmol/h per 10 ml. The methyl group of acetate was simultaneously metabolized to CH(4) and CO(2) in the anaerobic portions of the lake. Acetate oxidation was greatest in surface waters and decreased with water depth. Acetate was metabolized primarily to methane in the sediments and water immediately above the sediment. Sulfide inhibition studies and temperature activity profiles demonstrated that acetate metabolism was performed by several microbial populations. Sulfide additions (less than 5 mug/ml) to water from 21.5 m stimulated methanogenesis from acetate, but inhibited CO(2) production. Sulfate addition (1 mM) had no significant effect on acetate metabolism in water from 21.5 m, whereas nitrate additions (10 to 14,000 mug/liter) completely inhibited methanogenesis and stimulated CO(2) formation.

Acetates↗
PubMed1977

Effect of sulfate on carbon and electron flow during microbial methanogenesis in freshwater sediments.

The effect of sulfate on methane production in Lake Mendota sediments was investigated to clarify the mechanism of sulfate inhibition of methanogenesis. Methanogenesis was shown to be inhibited by the addition of as little as 0.2 mM sulfate. Sulfate inhibition was reversed by the addition of either H2 or acetate. Methane evolved when inhibition was reversed by H2 additions was derived from 14CO2. Conversely, when acetate was added to overcome sulfate inhibition, the evolved methane was derived from [2-14C]acetate. A competition for available H2 and acetate was proposed as the mechanism by which sulfate inhibited methanogenesis. Acetate was shown to be metabolized even in the absence of methanogenic activity. In the presence of sulfate, the methyl position of acetate was converted to CO2. The addition of sulfate to sediments did not result in the accumulation of significant amounts of sulfide in the pore water. Sulfate additions did not inhibit methanogenesis unless greater than 100 mug of free sulfide per ml was present in the pore water. These results indicate that carbon and electron flow are altered when sulfate is added to sediments. Sulfate-reducing organisms appear to assume the role of methanogenic bacteria in sulfate-containing sediments by utilizing methanogenic precursors.

Acetates↗
PubMed1978

Hydrogen as a substrate for methanogenesis and sulphate reduction in anaerobic saltmarsh sediment.

Hydrogen gas stimulated sulphate reduction in a saltmarsh sediment and the importance of H2 transferred from organotrophic bacteria to the sulphate-reducers is discussed. beta-fluorolactate inhibited sulphate reduction whether lactate, ethanol or hydrogen was being used as growth substrate. When added to sediment beta-fluorolactate inhibited sulphate reduction with a consequent increase in methane production. Addition of H2 stimulated methanogenesis in sediment and this stimulation was greater if CO2 was also present. Hydrogen availability was the primary limitation of methanogenesis but the low concentration of dissolved CO2 in seawater may limit methane production even if H2 is available. The removal of inhibition of methanogenesis by the use of fluorolactate to suppress sulphate reduction or by the provision of hydrogen indicates competitive inhibition of methanogens by sulphate reducers utilizing transferred hydrogen.

Desulfovibrio↗
PubMed1977

Association of hydrogen metabolism with methanogenesis in Lake Mendota sediments.

Lake Mendota sediments were studied to determine the role of H2 in sediment methanogenesis. H2 was generally not detectable in sediment. The addition of H2 to sediment significantly increased methanogenensis. The amount of methane produced was proportional to the concentration of hydrogen added. H2 addition stimulated the reduction of CO2 to methane, but did not significantly stimulate the conversion of methanol or the methyl position of acetate to methane. Various organic compounds also stimulated sediment methanogenesis. Formate, ethanol, and glucose were shown to serve as electron donors for CO2 reduction to methane. The addition of formate to sediment resulted in H2 evolution. H2 was not deith the phenomenon of interspecies hydrogen transfer. The results indicate that hydrogen is an important intermediate and a rate-limiting factor in sediment methanogenesis.

Acetates↗
PubMed1978

Methanogenesis from acetate: enrichment studies.

An acetate enrichment culture was initiated by inoculating anaerobic sludge from a mesophilic methane digestor into a mineral salts medium with calcium acetate as the sole carbon and energy source. This enrichment was maintained indefinitely by weekly transfer into medium of the same composition. A study of this enrichment disclosed an unexpected age-dependent inhibition of methanogenesis by H2 and formate which apparently differed from the inhibition by chloroform and benzyl viologen. This age-dependent inhibition indicated that microbial interactions of the mixed enrichment population may play a regulatory role in methane formation. Futhermore, stimulation of methanogenesis in the acetate enrichment by addition of yeast extract showed a nutrient limitation which indicated that syntrophic interactions leading to formation of growth factors may also occur. A model is presented to illustrate the possible interrelationships between methanogenic and nonmethanogenic bacteria in their growth and formation of methane and carbon dioxide from acetate.

Acetates↗
PubMed1978

Inhibition of methanogenesis by sulphate reducing bacteria competing for transferred hydrogen.

A methanogenic bacterial consortium was obtained after inoculation of benzoate medium under N2/CO2 atmosphere with intertidal sediment. A hydrogen donating organotroph and Methanococcus mazei were isolated from this enrichment. H2-utilising sulphate reducing bacteria were isolated under H2/CO2 in the absence of organic electron donors. The Methanococcus was able to produce methane in yeast extract medium under N2/CO2 if the H2 donating organism was present, and sulphate reduction occurred if the hydrogen utilising sulphate reducing bacteria were grown with the H2 donating organism. The ability of the H2 utilising sulphate reducing bacteria to inhibit Methanococcus competitively was shown in clutures containing both of these H2 utilising bacteria.

Bacteria↗
PubMed2024

Metagenome reveals the possible mechanism that microbial strains promote methanogenesis during anaerobic digestion of food waste.

For better understanding the mechanism of microbial strains promoting methane production, four strains Hungatella xylanolytica A5, Bacillus licheniformis B1, Paraclostridium benzoelyticum C2 and Advenella faeciporci E1 were inoculated into anaerobic digestion systems. After bioaugmentation, the cumulative methane production of A5, B1, C2 and E1 groups elevated by 11.68%, 8.20%, 18.21% and 15.67% compared to CK group, respectively. The metagenomic analysis revealed that the species diversity and uniformity of the experimental groups was improved, and hydrolytic acidifying bacteria, represented by Clostridiaceae, Anaerolineaceae and Oscillospiraceae, and methanogens, such as Methanotrichaceae and Methanobacteriaceae, were enriched. Meanwhile, the abundance of key genes in carbohydrate, pyruvate and methane metabolism was increased in the inoculated groups, providing reasonable reasons for more methane production. The strengthening mechanism of microbial strains in this study offered a theoretical foundation for selecting a suitable bioaugmentation strategy to solve the problems of slow start-up and low methane production in anaerobic digestion.

Methane↗
PubMed1978

Methanogenesis from acetate: a nonmethanogenic bacterium from an anaerobic acetate enrichment.

A methanogenic acetate enrichment was initiated by inoculation of an acetate-mineral salts medium with domestic anaerobic digestor sludge and maintained by weekly transfer for 2 years. The enrichment culture contained a Methanosarcina and several obligately anaerobic nonmethanogenic bacteria. These latter organisms formed varying degrees of association with the Methanosarcina, ranging from the nutritionally fastidious gram-negative rod called the satellite bacterium to the nutritionally nonfastidious Eubacterium limosum. The satellite bacterium had growth requirements for amino acids, a peptide, a purine base, vitamin B12, and other B vitamins. Glucose, mannitol, starch, pyruvate, cysteine, lysine, leucine, isoleucine, arginine, and asparagine stimulated growth and hydrogen production. Acetate was neither incorporated nor metabolized by the satellite organism. Since acetate was the sole organic carbon source in the enrichment culture, organism(s) which metabolize acetate (such as the Methanosarcina) must produce substrates and growth factors for associated organisms which do not metabolize acetate.

Acetates↗
PubMed2026

Feedstock-specific effects of sulfur-rich vegetable fractions on food waste anaerobic digestion: Sulfide-associated redox perturbation and adaptive microbial reassembly.

Food waste (FW) anaerobic digestion (AD) is strongly affected by feedstock heterogeneity, yet the role of sulfur-rich vegetable fractions remains poorly defined. Here, garlic (GAR), Chinese cabbage (CHC), and cabbage (CAB) were used as representative sulfur-rich vegetables to assess their effects on methane production, redox status, and microbial function during FW AD. At equal volatile solids loading, GAR showed no significant effect, whereas CHC and CAB caused a biphasic response, with delayed methane accumulation and reduced cumulative yield followed by late-stage daily methane production 39.6% and 45.9% higher than the control, respectively. CHC and CAB promoted sulfide accumulation and elevated reactive oxygen species (ROS) during the early stage. Elevated ROS levels were associated with lower NADH/NAD+ ratios, reduced electron transport activity, and volatile fatty acid accumulation, collectively indicating a redox-perturbed state characterized by functional decoupling between acidogenesis and methanogenesis. Metagenomic analysis showed that this early disturbance was followed by functional reassembly of the community. Hydrolytic-acidogenic bacteria sustained fermentation, accompanied by enrichment of genes associated with PFOR-Rnf-mediated energy conservation and the ED and oxidative PPP pathways, while methanogenesis shifted toward acetoclastic and methylotrophic routes. Genome-resolved analysis attributed the genomic potential for PFOR-Rnf-mediated energy conservation to Aminobacterium and Defluviitoga MAGs, and showed that Methanosarcina possessed the broadest oxidative stress defense repertoire, supporting its dominance after ROS perturbation. These findings provide a mechanistic framework linking sulfur-rich feedstock heterogeneity to methane-production dynamics, involving sulfide-associated redox perturbation and subsequent microbial functional reassembly.

Energy conservation↗
PubMed2026

Evidence of direct methane production from long-chain fatty acids by thermophilic Archaeoglobi.

Methanogenic degradation of long-chain fatty acids has traditionally been thought to occur through syntrophic partnerships between fatty acid-degrading bacteria and methanogenic archaea. However, recent genomic evidence suggests that certain archaea may independently carry out the entire process. Here we report the enrichment of an archaeon from the class Archaeoglobi, Candidatus Methanoglobus sphaerolipidus DLY3, from hot spring sediments in Tengchong, China. The results of selective enrichment, growth experiments, microscopy, stable isotope tracing, metagenomics and metatranscriptomics suggest that Ca. M. sphaerolipidus directly converts long-chain fatty acids to methane. This transformation involves the beta-oxidation pathway, the Wood-Ljungdahl pathway and methanogenic methyl-coenzyme M reductase and methyltransferase complexes-a process we term liparotrophy. In addition to oleic acid, Ca. M. sphaerolipidus is also capable of utilizing methanol as a substrate for methanogenesis. Our findings expand the known substrate range for methanogenic archaea beyond carbon dioxide reduction, acetoclastic methanogenesis, methylotrophy, methyl reduction, methoxydotrophy and the recently reported alkylotrophy.

Journal Article↗
PubMed1979

Methane synthesis without the addition of adenosine triphosphate by cell membranes isolated from Methanobacterium ruminantium.

The membrane fraction isolated from broken cells of Methanobacterium ruminantium actively synthesized methane from CO2 and H2 without the addition of ATP or other cofactors. This activity was lost unless strictly anaerobic conditions were maintained throughout the isolation and incubation procedures. 3H2, but not 3H2O, was readily incorporated into methane. This indicates that hydrogen atoms are used in the formation of methane without the prior equilibration of protons with the water phase. Methylenetetrahydrofolate was shown to be converted into methane, but less efficiently than CO2. The evidence indicates that tetrahydrofolate derivatives may not be of primary importance in the formation of methane from CO2 and H2. No requirement for ATP in methanogenesis could be demonstrated. However, chemical reagents that can increase proton conductance in membranes and therby abolish the membrane electrical potential were also effective inhibitors of methanogenesis. It was postulated that, although the reduction of CO2 to methane by bacterial membranes may require energy derived from a transmembrane potential, this does not appear to be coupled to the intermediary synthesis of ATP.

Adenine Nucleotides↗
PubMed1977

Thermophilic methane production from cattle waste.

Methane production from waste of cattle fed a finishing diet was investigated, using four 3-liter-working volume anaerobic digestors at 60 degrees C. At 55 degrees C a start-up culture, in which waste was the only source of bacteria, was generated within 8 days and readily adapted to 60 degrees C, where efficiency of methanogenesis was greater. Increasing the temperature from 60 to 65 degrees C tended to drastically lower efficiency. When feed concentrations of volatile solids (VS, organic matter) were increased in steps of 2% after holding for 1 months at a given concentration, the maximum concentrations for efficient fermentation were 8.2, 10.0, 11.6, and 11.6% for the retention times (RT) of 3, 6, 9, and 12 days, respectively. The VS destructions for these and lower feed concentrations were 31 to 37, 36 to 40, 47 to 49 and 51 to 53% for the 3-, 6-, 9-, and 12-day RT digestors, respectively, and the corresponding methane production rates were about 0.16, 0.18, 0.20, and 0.22 liters/day per g of VS in the feed. Gas contained 52 to 57% methane. At the above RT and feed concentrations, alkalinity rose to 5,000 to 7,700 mg of CaCo3 per liter (pH to 7.5 to 7.8), NH3 plus NH4+ to 64 to 90 mM, and total volatile acids to 850 to 2,050 mg/liter as acetate. The 3-day RT digestor was quite stable up to 8.2% feed VS and at this feed concentration produced methane at the very high rate of 4.5 liters/day per liter of digestor. Increasing the percentage of feed VS beyond those values indicated above resulted in greatly decreased organic matter destruction and methane production, variable decrease in pH, and increased alkalinity, ammonia, and total volatile acid concentrations, with propionate being the first to accumulate in large amounts. In a second experiment with another lot of waste, the results were similar. These studies indicate that loading rates can be much higher than those previously thought useful for maximizing methanogenesis from cattle waste.

Anaerobiosis↗