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Showing papers on "Methanogen published in 1997"


Journal ArticleDOI
TL;DR: Methanogenesis per ciliate protozoan and most probable numbers (MPN) of methanogens per c affiliate were measured and observed to be affected by feeding and indicated that apparent methane production by ciliates depended primarily on the number of meethanogens associated with them.

75 citations


Journal ArticleDOI
TL;DR: Because the phenomenon of sodium toxicity antagonism by betaine was demonstrated in anaerobic batch reactors, CSTRs, fluidized bed reactors, and UASB reactors, the usefulness of betaine in an industrial application may be feasible.

53 citations


Journal ArticleDOI
TL;DR: In this paper, an unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures.
Abstract: Interactions involving hydrogen transfer were studied in a coculture of two hyperthermophilic microorganisms: Thermotoga maritima, an anaerobic heterotroph, and Methanococcus jannaschii, a hydrogenotrophic methanogen. Cell densities of T. maritima increased 10-fold when cocultured with M. jannaschii at 85 degrees C, and the methanogen was able to grow in the absence of externally supplied H(2) and CO(2). The coculture could not be established if the two organisms were physically separated by a dialysis membrane, suggesting the importance of spatial proximity. The significance of spatial proximity was also supported by cell cytometry, where the methanogen was only found in cell sorts at or above 4.5 microm in samples of the coculture in exponential phase. An unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures. Calculations suggest the increases in methanogenesis rates with temperature result from greater interactions between the methanogenic and fermentative organisms, as evidenced by the sharp decline in H(2) concentration in the proximity of a hyperthermophilic methanogen. The experimental and modeling results presented here illustrate the need to consider the interactions within hyperthermophilic consortia when choosing isolation strategies and evaluating biotransformations at elevated temperatures.

47 citations


Journal ArticleDOI
TL;DR: Using experimental approaches based on DNA sequences identifying either methanogen‐specific or methanotroph‐specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments, focused on blanket bog peat.
Abstract: The role of methane as a greenhouse gas and the contribution of bacteria to the production (methanogenesis) and destruction (methane oxidation) of methane is described. Using experimental approaches based on DNA sequences identifying either methanogen-specific or methanotroph-specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments. These methods were focused on blanket bog peat but are suitable for other environments. In addition to group specific 16S rRNA DNA sequences, specific functional gene probes based on methane coenzyme reductase sequences for methanogens and methane monooxygenase sequences for methanotrophs, were developed. These sequences were used in PCR-based protocols to detect and amplify specific gene sequences from the total DNA isolated from transverse sections of blanket bog peat. This permitted the analysis of the vertical distribution of methanogen and methanotroph populations, discrimination between different sub-sets of these populations, and the identification of novel organisms not previously detected by culture-based methods.

37 citations


Journal ArticleDOI
TL;DR: The metabolic activities of both the sulfate-reducing bacteria and the methanogenic bacteria were essential for complete degradation of phenol in an anaerobic bacterial consortium isolated from swine manure.
Abstract: Swine manure contains diverse groups of aerobic and anaerobic bacteria. An anaerobic bacterial consortium containing sulfate-reducing bacteria (SRB) and acetate-utilizing methanogenic bacteria was isolated from swine manure. This consortium used phenol as its sole source of carbon and converted it to methane and CO2. The sulfate-reducing bacterial members of the consortium are the incomplete oxidizers, unable to carry out the terminal oxidation of organic substrates, leaving acetic acid as the end product. The methanogenic bacteria of the consortium converted the acetic acid to methane. When a methanogen inhibitor was used in the culture medium, phenol was converted to acetic acid by the SRB, but the acetic acid did not undergo further metabolism. On the other hand, when the growth of SRB in the consortium was suppressed with a specific SRB inhibitor, namely, molybdenum tetroxide, the phenol was not degraded. Thus, the metabolic activities of both the sulfate-reducing bacteria and the methanogenic bacteria were essential for complete degradation of phenol.

32 citations


Journal ArticleDOI
TL;DR: Soils, which developed from different parent material and had various use history, had notably different cell numbers and activities of methanogenic bacteria, and those in upland soil were pronounced lower than those in rice soil.
Abstract: The population, methanogenic activities and dominant species of methanogenic bacteria in paddy rice soils under different conditions were studied. Application of fertilizer, especially organic manure and submergence with deep water increased the population and methanogenic activities of methanogenic bacteria in rice soils. No large differences was observed among the population of methanogen in rice soils from different depths of 0-5, 5-13 and 13-18 cm. Soils, which developed from different parent material and had various use history, had notably different cell numbers and activities of methanogenic bacteria. Methanogenic activities in soils developed from fluvo-aquic soil were obviously higher than those in soils developed from quaternary red soil and coastal saline soil, and those in upland soil were pronounced lower than those in rice soil. The methanogenic bacteria that survived in air-dried rice soil could form methane after addition of water and incubation. The dominant species of methanogens were Methanobacterium formicicum, Methanobrevibacter sp., Methanosarcina mazeii and Methanosarcina barkeri.

22 citations


Journal ArticleDOI
TL;DR: The results suggest that the endosymbiotic methanogens which function as hydrogen scavengers are not indispensable for the growth and survival of T. compressum, although the growth yield decreased slightly in the absence of methanogen, and the ciliate is capable of fermenting food bacteria without endosyrate by changing its metabolic pathway.
Abstract: We examined the influence of endosymbiotic methanogens on the growth and metabolic profile of the anaerobic ciliate Trimyema compressum When we isolated the ciliate, it possessed a large number of endosymbiotic Methanobacterium-like methanogens inside the cell The culture was transferred to fresh medium with Lactobacillus sp cells as food bacteria T compressum grew to give a maximum cell number of 3300 cells/ml without loss of the endosymbionts over 30 passages of transfer Acetate and methane were major end products with smaller amounts of propionate and butyrate However, after further continued cultivation, the number of endosymbiotic methanogens started to decrease and they eventually disappeared The growth and metabolic profile of the ciliate were changed significantly as the symbiotic association deteriorated The major fermentation products were shifted to butyrate These results suggest that the endosymbiotic methanogens which function as hydrogen scavengers are not indispensable for the growth and survival of T compressum, although the growth yield decreased slightly in the absence of methanogens, and the ciliate is capable of fermenting food bacteria without endosymbiotic methanogens by changing its metabolic pathway

17 citations


Journal ArticleDOI
TL;DR: Thermophilic (75°C), anaerobic biodegradation of chlorobenzoates was investigated using different inocula from geothermal and non‐geothermal environments, resulting in the first reported biotransformation of this chlorinated aromatic at a temperature of 75°C.
Abstract: Thermophilic (75 degrees C), anaerobic biodegradation of chlorobenzoates was investigated using different inocula from geothermal and non-geothermal environments. Microbial dehalogenation of 3-chlorobenzoate (0.5 mmol l-1 was achieved by two mixed cultures growing anaerobically at 75 degrees C. One culture consisted of a facultative anaerobe and two obligate anaerobes, one of which was a methanogen, isolated from terrestrial sediments from hot springs in New Zealand. The other culture, derived from a non-geothermal environment, consisted of a Clostridium spp. and a non-spore-forming obligate anaerobe. No degradation of either 2-chlorobenzoate or 4-chlorobenzoate was achieved by these thermophilic cultures over the same time period. This is the first reported biotransformation of this chlorinated aromatic at a temperature of 75 degrees C.

8 citations


01 Jan 1997
TL;DR: Using experimental approaches based on DNA sequences identifying either methanogenspecific or methanotroph-specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments, focused on blanket bog peat.
Abstract: The role of methane as a greenhouse gas and the contribution of bacteria to the production (methanogenesis) and destruction (methane oxidation) of methane is described. Using experimental approaches based on DNA sequences identifying either methanogenspecific or methanotroph-specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments. These methods were focused on blanket bog peat but are suitable for other environments. In addition to group specific 16S rRNA DNA sequences, specific functional gene probes based on methane coenzyme reductase sequences for methanogens and methane monooxygenase sequences for methanotrophs, were developed. These sequences were used in PCR-based protocols to detect and amplify specific gene sequences from the total DNA isolated from transverse sections of blanket bog peat. This permitted the analysis of the vertical distribution of methanogen and methanotroph populations, discrimination between different sub-sets of these populations, and the identification of novel organisms not previously detected by culture-based methods.