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PubMed2006

Effect of phosphogypsum on respiration and methane emissions in sediment.

The impact of adding phosphogypsum (PG) to freshwater wetland areas, and potential effect on methane production and respiration in sediment was studied in the laboratory. Two organic matter levels (native and enriched with 0.5% by weight ground dry plant material) were studied using five sediment treatments each: (1) no PG added, (2) 4% PG by dry weight (homogenized), (3) 20% PG by dry weight (homogenized), (4) 2000 kg ha(-1) (surface applied), and (5) 5000 kg ha (surface applied), and the experiment was run in triplicate. There was a net flux of methane into sediment for all treatments that were maintained at the native organic matter level, indicating net methane oxidation. In the organic-enriched cores, both of the homogenized treatments exhibited no methane emissions, while the surface applied treatments retained the potential for high emissions. Soil respiration was depressed in all treatments when compared to controls, especially in the organic-enriched cores. The results conclude that it may be possible to add PG to non-vegetated areas with few observable effects on sediment respiration, but organic matter content and method of application are critical concerns.

Calcium Sulfate↗

PubMed1994

Effect of resistant starch on breath-hydrogen and methane excretion in healthy volunteers.

Colonic fermentation of dietary carbohydrates and fiber might produce a protective effect against the development of large bowel cancer. Resistant starch, ie, starch that escapes small bowel digestion, is a candidate fermentable substrate that has been hitherto little studied. We supplemented 19 healthy volunteers with 15 g native amylomaize (Hylon-VII) three times a day, containing 28 g type II resistant starch, or with dextrins as a placebo for 7 d in a crossover design. Pre-experimentally, 11 subjects regularly produced breath methane and 8 did not. Resistant starch increased 24-h integrated excretion of breath hydrogen. The mean rise relative to placebo was 35% (P = 0.03) for all subjects and 60% for eight subjects not producing methane (P = 0.02). The 11 methane producers showed a 93% increase in breath-methane excretion on resistant starch (P = 0.03). Continued consumption of 28 g type II resistant starch/d is well tolerated and increases colonic fermentation in healthy volunteers.

Adult↗

PubMed1998

Breath hydrogen and methane expiration in men and women after oat extract consumption.

Oat extract has been shown to modify blood glucose response and fasting lipids after dietary incorporation although some abdominal discomfort and increased flatulence were noted. To determine the extent of gas production, hydrogen and methane were determined after tolerance tests containing cooked and uncooked oat extract and after dietary incorporation. Breath gases were determined before and periodically after tolerance tests. Study 1: While consuming a maintenance diet, 24 subjects (55.3-112.5 kg body weight) underwent a tolerance test (1 g carbohydrate/kg body wt) of glucose (GTT, 1700 kJ/100 g) or uncooked, baked, or boiled pudding [2191 kJ/100 g carbohydrate, (0.67 glucose and 0.33 oat extract containing 10 g/100 g beta-glucan)]. Hydrogen and methane expiration after all tolerance tests with the oat extract puddings, regardless of cooking method, was significantly higher than expirations after the GTT. Cooking the oat extract did not significantly change hydrogen or methane expiration. Study 2: Twenty-three subjects consumed a maintenance diet followed by the incorporation of oat extracts (50 g/8.33 MJ, 1 or 10 g/100 g beta-glucan) to the diet in a crossover pattern. A GTT and a tolerance test containing 0.67 g glucose and 0.33 g of the respective oat extract/kg body weight were consumed after the maintenance and oat extract diet periods. Breath hydrogen was significantly higher after both oat extract tolerance tests than after the GTT. Hydrogen excretion after the 10% beta-glucan oat extract was higher at 4, 5 and 6 h than after the 1% beta-glucan oat extract; breath methane was not significantly different. These data indicate that cooking did not alter the influence of oat extracts on intestinal function, and increased beta-glucan marginally increased hydrogen expiration.

Adult↗

PubMed1998

Increased serum cholesterol in healthy human methane producers is confounded by age.

It has been theorized that colonic production and absorption of short-chain fatty acids (SCFA) is different in methane producers (MP) compared with nonproducers (MNP). Because colonic SCFA may influence systemic lipid metabolism, blood lipids may differ in MP and MNP. To compare serum lipids and SCFA in fasting MP and MNP, we measured breath gases, serum lipids and SCFA in 167 healthy subjects and excluded subjects with abnormal blood lipids. The 66 MP were significantly older than the 63 MNP (49.5 +/- 16.0 vs. 39.6 +/- 17.0 y, P = 0.0009), and breath methane concentrations were weakly correlated with age in MP (r = 0.268, P = 0.03). Mean serum cholesterol was significantly higher in MP compared with MNP, but the differences were not significant after adjusting for age. No significant differences were observed in serum SCFA between the two groups. This study has shown that breath methane increases with age, which may be due to age-related increases in transit time and carbohydrate malabsorption. These results provide no conclusive link between colonic events and serum lipids in MP because, with age, methane production increased as did serum cholesterol. More research is required before any definite conclusions can be drawn.

Adult↗

PubMed2003

Simultaneous generation of methane, carbon dioxide, and carbon monoxide from choline and ascorbic acid: a defensive mechanism against reductive stress?

Indirect evidence suggests that an abnormal increase in reducing power (reductive stress) may be associated with abnormal clinical states. We have recently proposed that under such conditions biomolecules with electrophilic methyl groups (EMGs) bound to positively charged nitrogen or sulfur moieties may act as electron acceptors and that this poising mechanism may entail the generation of methane gas. Here we report for the first time the generation of methane by rat liver mitochondria. We also report the formation of methane from choline in the presence of hydrogen peroxide, catalytic iron, and ascorbic acid. In this system, carbon monoxide and carbon dioxide are formed from the ascorbate molecule in parallel with methane generation. In view of these findings, we try to explain the essential role of biomolecules with EMG moiety. We hypothesize that this concerted reaction may be a defensive response to reductive stress and may provide the protection needed against redox imbalance in living systems.

Animals↗

PubMed1992

Death scene gas analysis in suspected methane asphyxia.

Two cases of methane asphyxia occurring in two boys (age 11 and 12 years) who were found at the bottom of a 37-ft (11.1-m)-deep sewer shaft are described. Attempted resuscitation of the first patient was unsuccessful and achieved only temporary stabilization of the second, who died 48 h after his discovery. Autopsies revealed relatively minor multifocal traumatic injuries, with evidence of hypoxic-ischemic encephalopathy in the patient who survived for 2 days. Subsequent analysis of gas in the shaft revealed 21% oxygen at the surface, 14.3% at a depth of 5 ft (1.5 m), and only 4.8% at depths of 10 ft (3 m) and below. Other gases detected at the lower levels were methane, nitrogen, and carbon dioxide (4.3%). These cases demonstrate the value of atmospheric gas analysis in cases of possible methane asphyxia in confirming the presence of methane and in demonstrating levels of oxygen below that necessary to support life.

Accidental Falls↗

PubMedDate not supplied

Methane production in patients with cystic fibrosis.

Methane production was studied in 28 cystic fibrosis patients aged 3-16 years and in 290 healthy children. The percentages of methane producers in the cystic fibrosis and control groups were 60.7 and 20.6%, respectively. In the patient group there was no difference between methane producers and nonproducers with respect to the degree of malabsorption or the administration of pancreatic supplements or antibiotics. We hypothesize that the high proportion of methane producers in cystic fibrosis patients may be associated with the presence of specific substrate(s) (glycoprotein?) in their intestinal contents. Changes of the intestinal microenvironment may favor the development of a methanogenic flora.

Adolescent↗

PubMed1999

Ineffectiveness of breath methane excretion as a diagnostic test for lactose malabsorption.

BACKGROUND: In clinical and field conditions, breath gas analysis has been widely used in evaluating carbohydrate digestion. A field study was performed to determine the prevalence of lactose malabsorption in Myanmar children and to evaluate the possibility of using breath methane excretion to indicate lactose malabsorption in a field situation. METHODS: The study population consisted of 118 children aged 1 to 12 years. A hydrogen breath test after a lactose meal (2 g/kg, maximum 50 g) was used as a standard test. RESULTS: Lactose malabsorption was detected in 16.7% of children aged 1 to 2.9 years, with the prevalence increasing with age from 40.5% of those aged 3 to 5.9 years to 88.5% of those aged 6 to 8.9 years and reaching 91.7% in those aged 9 to 11.9 years. Lactose malabsorption was more prevalent when children were weaned before 4 months of age (87.2 vs. 41.1%; p < 0.01). Compared with lactose-tolerant children, those with lactose malabsorption had significantly higher concentrations of breath hydrogen excretion 60 minutes after the lactose test meal. Breath methane excretion was also significantly higher in samples at 120 minutes in children with lactose malabsorption. Breath methane excretion of greater than or equal to 2 parts per million at 180 minutes as a diagnostic test for lactose malabsorption had a sensitivity of 61.5% and a specificity of 84.6%. CONCLUSION: The breath methane test for lactose malabsorption has a lower sensitivity and specificity than the breath hydrogen test and therefore does not replace the lactose breath hydrogen test.

Breath Tests↗

PubMed2002

Methylocapsa acidiphila gen. nov., sp. nov., a novel methane-oxidizing and dinitrogen-fixing acidophilic bacterium from Sphagnum bog.

A novel genus and species, Methylocapsa acidiphila gen. nov., sp. nov., are proposed for a methane-oxidizing bacterium isolated from an acidic Sphagnum peat bog. This bacterium, designated strain B2T, represents aerobic, gram-negative, colourless, non-motile, curved coccoids that form conglomerates covered by an extracellular polysaccharide matrix. The cells use methane and methanol as sole sources of carbon and energy and utilize the serine pathway for carbon assimilation. Strain B2T is a moderately acidophilic organism with growth between pH 4.2 and 7.2 and at temperatures from 10 to 30 degrees C. The cells possess a well-developed system of intracytoplasmic membranes (ICM) packed in parallel on only one side of the cell membrane. This type of ICM structure represents a novel arrangement, which was termed type III. The resting cells are Azotobacter-type cysts. Strain B2T is capable of atmospheric nitrogen fixation; it possesses particulate methane monooxygenase and does not express soluble methane monooxygenase. The major phospholipid fatty acid is 18:1omega7c and the major phospholipids are phosphatidylglycerols. The G+C content of the DNA is 63.1 mol%. This bacterium belongs to the alpha-subclass of the Proteobacteria and is most closely related to the acidophilic methanotroph Methylocella palustris KT (97.3% 16S rDNA sequence similarity). However, the DNA-DNA hybridization value between strain B2T and Methylocella palustris K(T) is only 7%. Thus, strain B2T is proposed to comprise a novel genus and species, Methylocapsa acidiphila gen. nov., sp. nov. Strain B2T (= DSM 13967T = NCIMB 13765T) is the type strain.

Bryopsida↗

PubMed2002

Molecular phylogeny of type II methane-oxidizing bacteria isolated from various environments.

Type II methane-oxidizing bacteria (MOB) were isolated from diverse environments, including rice paddies, pristine and polluted freshwaters and sediments, mangrove roots, upland soils, brackish water ecosystems, moors, oil wells, water purification systems and livestock manure. Isolates were identified based on morphological traits as either Methylocystis spp., Methylosinus sporium or Methylosinus trichosporium. Molecular phylogenies were constructed based on nearly complete 16S rRNA gene sequences, and on partial sequences of genes encoding PmoA (a subunit of particulate methane monooxygenase), MxaF (a subunit of methanol dehydrogenase) and MmoX (a subunit of soluble methane monooxygenase). The maximum pairwise 16S rDNA difference between isolates was 4.2%, and considerable variability was evident within the Methylocystis (maximum difference 3.6%). Due to this variability, some of the published 'specific' oligonucleotide primers for type II MOB exhibit multiple mismatches with gene sequences from some isolates. The phylogenetic tree constructed from pmoA gene sequences closely mirrored that constructed from 16S rDNA sequences, and both supported the presently accepted taxonomy of type II MOB. Contrary to previously published phylogenetic trees, morphologically distinguishable species were generally monophyletic based on pmoA or 16S rRNA gene sequences. This was not true for phylogenies constructed from mmoX and mxaF gene sequences. The phylogeny of mxaF gene sequences suggested that horizontal transfer of this gene may have occurred across type II MOB species. Soluble methane monooxygenase could not be detected in many Methylocystis strains either by an enzyme activity test (oxidation of naphthalene) or by PCR-based amplification of an mmoX gene.

Alphaproteobacteria↗

PubMed1995

Detection of novel marine methanotrophs using phylogenetic and functional gene probes after methane enrichment.

A major limitation of rRNA-targeted group-specific probes is that they may cross-react with organisms of other physiological, or even phylogenetic groups when applied to environmental samples containing unknown sequences. We have exploited the restricted physiology of methane-oxidizing bacteria to assess the specificity and efficiency of probes for this physiological type which target the 16S rRNA or genes involved in methanotroph physiology. Seawater samples were enriched for methanotrophs by addition of methane and essential nutrients. The changes in composition of the bacterial population were monitored by analysis of 16S rRNA gene libraries. Methanotroph group-specific probes failed to give a signal with samples from these enrichments even though a methanol dehydrogenase structural gene was detected. A 16S rDNA sequence that was abundant only after methane addition was recovered and found to show a close phylogenetic relationship to Methylomonas. Organisms containing this sequence were observed in enrichments by in situ hybridization. The combination of enrichment on methane and screening with the broad specificity methanol dehydrogenase probe allowed detection of novel methanotrophs that were not detected with the original suite of methanotroph group-specific probes.

Alcohol Oxidoreductases↗

PubMed2003

Molecular fossil record of elevated methane levels in late Pleistocene coastal waters.

Accumulating evidence suggests that methane has been released episodically from hydrates trapped in sea floor sediments during many intervals of rapid climate warming. Here we show that sediments from the Santa Barbara Basin deposited during warm intervals in the last glacial period contain molecular fossils that are diagnostic of aerobic and anaerobic methanotrophs. Sediment intervals with high abundances of these compounds indicate episodes of vigorous methanotrophic activity in methane-laden water masses. Signals for anaerobic methanotrophy in 44,100-year-old sediment are evidence for particularly intense methane emissions and suggest that the basin's methane cycle can profoundly affect oxygen budgets in the water column.

Aerobiosis↗

PubMed1998

Isolation of acidophilic methane-oxidizing bacteria from northern peat wetlands.

Acidic northern wetlands are an important source of methane, one of the gases that contributes to global warming. Methane oxidation in the surface of these acidic wetlands can reduce the methane flux to the atmosphere up to 90 percent. Here the isolation of three methanotrophic microorganisms from three boreal forest sites is reported. They are moderately acidophilic organisms and have a soluble methane monooxygenase. In contrast to the known groups of methanotrophs, 16S ribosomal DNA sequence analysis shows that they are affiliated with the acidophilic heterotrophic bacterium Beijerinckia indica subsp. indica.

Amino Acid Sequence↗

PubMed2006

Methane- and sulfur-metabolizing microbial communities dominate the Lost City hydrothermal field ecosystem.

Hydrothermal venting and the formation of carbonate chimneys in the Lost City hydrothermal field (LCHF) are driven predominantly by serpentinization reactions and cooling of mantle rocks, resulting in a highly reducing, high-pH environment with abundant dissolved hydrogen and methane. Phylogenetic and terminal restriction fragment length polymorphism analyses of 16S rRNA genes in fluids and carbonate material from this site indicate the presence of organisms similar to sulfur-oxidizing, sulfate-reducing, and methane-oxidizing Bacteria as well as methanogenic and anaerobic methane-oxidizing Archaea. The presence of these metabolic groups indicates that microbial cycling of sulfur and methane may be the dominant biogeochemical processes active within this ultramafic rock-hosted environment. 16S rRNA gene sequences grouping within the Methylobacter and Thiomicrospira clades were recovered from a chemically diverse suite of carbonate chimney and fluid samples. In contrast, 16S rRNA genes corresponding to the Lost City Methanosarcinales phylotype were found exclusively in high-temperature chimneys, while a phylotype of anaerobic methanotrophic Archaea (ANME-1) was restricted to lower-temperature, less vigorously venting sites. A hyperthermophilic habitat beneath the LCHF may be reflected by 16S rRNA gene sequences belonging to Thermococcales and uncultured Crenarchaeota identified in vent fluids. The finding of a diverse microbial ecosystem supported by the interaction of high-temperature, high-pH fluids resulting from serpentinization reactions in the subsurface provides insight into the biogeochemistry of what may be a pervasive process in ultramafic subseafloor environments.

Archaea↗

PubMed1986

Biodegradation of chlorinated ethenes by a methane-utilizing mixed culture.

Chlorinated ethenes are toxic substances which are widely distributed groundwater contaminants and are persistent in the subsurface environment. Reports on the biodegradation of these compounds under anaerobic conditions which might occur naturally in groundwater show that these substances degrade very slowly, if at all. Previous attempts to degrade chlorinated ethenes aerobically have produced conflicting results. A mixed culture containing methane-utilizing bacteria was obtained by methane enrichment of a sediment sample. Biodegradation experiments carried out in sealed culture bottles with radioactively labeled trichloroethylene (TCE) showed that approximately half of the radioactive carbon had been converted to 14CO2 and bacterial biomass. In addition to TCE, vinyl chloride and vinylidene chloride could be degraded to products which are not volatile chlorinated substances and are therefore likely to be further degraded to CO2. Two other chlorinated ethenes, cis and trans-1,2-dichloroethylene, were shown to degrade to chlorinated products, which appeared to degrade further. A sixth chlorinated ethene, tetrachloroethylene, was not degraded by the methane-utilizing culture under these conditions. The biodegradation of TCE was inhibited by acetylene, a specific inhibitor of methane oxidation by methanotrophs. This observation supported the hypothesis that a methanotroph is responsible for the observed biodegradations.

1-Propanol↗

PubMed1996

Biodegradation of individual and multiple chlorinated aliphatic hydrocarbons by methane-oxidizing cultures.

The microbial degradation of chlorinated and nonchlorinated methanes, ethanes, and ethanes by a mixed methane-oxidizing culture grown under chemostat and batch conditions is evaluated and compared with that by two pure methanotrophic strains: CAC1 (isolated from the mixed culture) and Methylosinus trichosporium OB3b. With the exception of 1,1-dichloroethylene, the transformation capacity (Tc) for each chlorinated aliphatic hydrocarbon was generally found to be in inverse proportion to its chlorine content within each aliphatic group (i.e., methanes, ethanes, and ethenes), whereas similar trends were not observed for degradation rate constants. Tc trends were similar for all methane-oxidizing cultures tested. None of the cultures were able to degrade the fully chlorinated aliphatics such as perchloroethylene and carbon tetrachloride. Of the four cultures tested, the chemostat-grown mixed culture exhibited the highest Tc for trichloroethylene, cis-1,2-dichloroethylene, tetrachloroethane, 1,1,1-trichloroethane, and 1,2-dichloroethane, whereas the pure batch-grown OB3b culture exhibited the highest Tc for all other compounds tested. The product toxicity of chlorinated aliphatic hydrocarbons in a mixture containing multiple compounds was cumulative and predictable when using parameters measured from the degradation of individual compounds. The Tc for each chlorinated aliphatic hydrocarbon in a mixture (Tcmix) and the total Tc for the mixture (sigma Tcmix) are functions of the individual Tc, the initial substrate concentration (S0), and the first-order rate constant (k/Ks) of each compound in the mixture, indicating the importance of identifying the properties and compositions of all potentially degradable compounds in a contaminant mixture.

Bacteria↗

PubMed1998

Effect of selected monoterpenes on methane oxidation, denitrification, and aerobic metabolism by bacteria in pure culture.

Selected monoterpenes inhibited methane oxidation by methanotrophs (Methylosinus trichosporium OB3b, Methylobacter luteus), denitrification by environmental isolates, and aerobic metabolism by several heterotrophic pure cultures. Inhibition occurred to various extents and was transient. Complete inhibition of methane oxidation by Methylosinus trichosporium OB3b with 1.1 mM (-)-alpha-pinene lasted for more than 2 days with a culture of optical density of 0.05 before activity resumed. Inhibition was greater under conditions under which particulate methane monooxygenase was expressed. No apparent consumption or conversion of monoterpenes by methanotrophs was detected by gas chromatography, and the reason that transient inhibition occurs is not clear. Aerobic metabolism by several heterotrophs was much less sensitive than methanotrophy was; Escherichia coli (optical density, 0.01), for example, was not affected by up to 7.3 mM (-)-alpha-pinene. The degree of inhibition was monoterpene and species dependent. Denitrification by isolates from a polluted sediment was not inhibited by 3.7 mM (-)-alpha-pinene, gamma-terpinene, or beta-myrcene, whereas 50 to 100% inhibition was observed for isolates from a temperate swamp soil. The inhibitory effect of monoterpenes on methane oxidation was greatest with unsaturated, cyclic hydrocarbon forms [e.g., (-)-alpha-pinene, (S)-(-)-limonene, (R)-(+)-limonene, and gamma-terpinene]. Lower levels of inhibition occurred with oxide and alcohol derivatives [(R)-(+)-limonene oxide, alpha-pinene oxide, linalool, alpha-terpineol] and a noncyclic hydrocarbon (beta-myrcene). Isomers of pinene inhibited activity to different extents. Given their natural sources, monoterpenes may be significant factors affecting bacterial activities in nature.

Aerobiosis↗

PubMed1998

Effect of nitrogen source on growth and trichloroethylene degradation by methane-oxidizing bacteria.

The effect of nitrogen source on methane-oxidizing bacteria with respect to cellular growth and trichloroethylene (TCE) degradation ability were examined. One mixed chemostat culture and two pure type II methane-oxidizing strains, Methylosinus trichosporium OB3b and strain CAC-2, which was isolated from the chemostat culture, were used in this study. All cultures were able to grow with each of three different nitrogen sources: ammonia, nitrate, and molecular nitrogen. Both M. trichosporium OB3b and strain CAC-2 showed slightly lower net cellular growth rates and cell yields but exhibited higher methane uptake rates, levels of poly-beta-hydroxybutyrate (PHB) production, and naphthalene oxidation rates when grown under nitrogen-fixing conditions. The TCE-degrading ability of each culture was measured in terms of initial TCE oxidation rates and TCE transformation capacities (mass of TCE degraded/biomass inactivated), measured both with and without external energy sources. Higher initial TCE oxidation rates and TCE transformation capacities were observed in nitrogen-fixing mixed, M. trichosporium OB3b, and CAC-2 cultures than in nitrate- or ammonia-supplied cells. TCE transformation capacities were found to correlate with cellular PHB content in all three cultures. The results of this study suggest that the nitrogen-fixing capabilities of methane-oxidizing bacteria can be used to select for high-activity TCE degraders for the enhancement of bioremediation in fixed-nitrogen-limited environments.

Ammonia↗