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L Daniels

Publications and source records attributed to L Daniels.

At least 73 records · Page 4Linked to original sources
PubMed1987

Production of ethane, ethylene, and acetylene from halogenated hydrocarbons by methanogenic bacteria.

Several methanogenic bacteria were shown to produce ethane, ethylene, and acetylene when exposed to the halogenated hydrocarbons bromoethane, dibromo- or dichloroethane, and 1,2-dibromoethylene, respectively. They also produced ethylene when exposed to the coenzyme M analog and specific methanogenic inhibitor bromoethanesulfonic acid. The production of these gases from halogenated hydrocarbons has a variety of implications concerning microbial ecology, agriculture, and toxic waste treatment. All halogenated aliphatic compounds tested were inhibitory to methanogens. Methanococcus thermolithotrophicus, Methanococcus deltae, and Methanobacterium thermoautotrophicum DeltaH and Marburg were completely inhibited by 7 muM 1,2-dibromoethane and, to various degrees, by 51 to 1,084 muM 1,2-dichloroethane, 1,2-dibromoethylene, 1,2-dichloroethylene, and trichloroethylene. In general, the brominated compounds were more inhibitory. The two Methanococcus species were fully inhibited by 1 muM bromoethanesulfonic acid, whereas both Methanobacterium strains were only partly inhibited by 2,124 muM. Coenzyme M protected cells from bromoethanesulfonic acid but not from any of the other inhibitors.

Journal Article↗
PubMed1987

Assessment of nutrient intake of patients with cystic fibrosis compared with healthy children.

The food intakes of 40 patients with cystic fibrosis (CF) (0.7 to 23 years) on low-fat diets were assessed in relation to the appropriate recommended dietary allowance (RDA) and intakes of healthy children. Mean energy intakes of the subjects with CF were similar to the control groups but fell well short of the frequently cited goal of 120-150 per cent of the RDA. Failure to achieve this may account for their marked growth failure. The study highlights the inability of CF patients to maintain a high energy intake despite nutritional counselling when dietary fat is restricted. When energy per kg body weight was considered, children with CF ate more than their peers and it may be unrealistic to expect them to increase their spontaneous oral intake above this level.

Adolescent↗
PubMed1986

31P-NMR spectra of methanogens: 2,3-cyclopyrophosphoglycerate is detectable only in methanobacteria strains.

The unique compound 2,3-cyclopyrophosphoglycerate occurs at a detectable concentration in the genera Methanobacterium and Methanobrevibacter but not in Methanococcus, Methanospirillum and Methanosarcina, as shown by a 31P-NMR survey of several different methanogens. Metabolic poisons (carbonyl cyanide m-chlorophenylhydrazone and valinomycin) do not decrease the level of the cyclic pyrophosphate in Methanobacterium thermoautotrophicum; therefore, it cannot be a phosphagen, i.e., an energy storage material. 13CO2 is rapidly incorporated into this cyclic compound which represents the major soluble carbon as well as the phosphorus component of this methanobacteria. 13C-NMR analysis demonstrates that the pKa of the 2,3-cyclopyrophosphoglycerate carboxyl group is 2.55. The unusual pseudomurein cell wall structure of methano- and methanobrevibacteria necessitates a high demand on carbohydrate metabolism. For this reason, and the fact that when its concentration is decreased no new phosphorus resonances appear in the high resolution spectra, it is suggested that 2,3-cyclopyrophosphoglycerate has a function in carbohydrate metabolism.

2,3-Diphosphoglycerate↗
PubMed1986

Assimilatory reduction of sulfate and sulfite by methanogenic bacteria.

A variety of sulfur-containing compounds were investigated for use as medium reductants and sulfur sources for growth of four methanogenic bacteria. Sulfide (1 to 2 mM) served all methanogens investigated well. Methanococcus thermolithotrophicus and Methanobacterium thermoautotrophicum Marburg and delta H grew well with S0, SO3(2-), or thiosulfate as the sole sulfur source. Only Methanococcus thermolithotrophicus was able to grow with SO4(2-) as the sole sulfur source. 2-Mercaptoethanol at 20 mM was greatly inhibitory to growth of Methanococcus thermolithotrophicus on SO4(2-) or SO2(2-) and Methanobacterium thermoautotrophicum Marburg on SO3(2-) but not to growth of strain delta H on SO3(2-). Sulfite was metabolized during growth by Methanococcus thermolithotrophicus. Sulfide was produced in cultures of Methanococcus thermolithotrophicus growing on SO4(2-), SO3(2-), thiosulfate, and S0. Methanobacterium thermoautotrophicum Marburg was successfully grown in a 10-liter fermentor with S0, SO3(2-), or thiosulfate as the sole sulfur source.

Euryarchaeota↗
PubMed1986

Variation in composition and yield of exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4.

The exopolysaccharides produced by Klebsiella sp. strain K32 and Acinetobacter calcoaceticus BD4 under different growth conditions have been analyzed for sugar composition. The first use of ion chromatography for the quantitative determination of microbial exopolysaccharide composition is reported. Klebsiella sp. strain K32 produced a polymer composed of rhamnose, galactose, and mannose early in its fermentation. The composition of the polymer varied markedly depending on the growth stage of the organism. Klebsiella sp. strain K32 grown in a fermentor produced a polymer which was rich in mannose during early exponential growth in a complex medium, but in the late stationary phase it did not contain detectable levels of mannose. The rhamnose present in the polymer increased from 12 to 55% over the course of growth, whereas galactose decreased from 63 to 45%. A. calcoaceticus BD4 produced a polymer containing rhamnose, glucose, mannose throughout its growth and stationary phase. Klebsiella sp. strain K32 and A. calcoaceticus BD4 were grown on various carbon sources in shake flasks. The polymer yield and composition from both organisms were found to vary with the carbon source. The exopolysaccharide with the highest mannose composition was obtained by using rhamnose as a carbon source for both organisms. These and other data suggest that regulatory changes caused by growth on different substrates result in either the production of a different distribution of polymers or a change in exopolysaccharide structure.

Acinetobacter↗
PubMed1986

Relationship of formate to growth and methanogenesis by Methanococcus thermolithotrophicus.

Methanococcus thermolithotrophicus is a methanogenic archaebacterium that can use either H2 or formate as its source of electrons for reduction of CO2 to methane. Growth and suspended-whole-cell experiments show that H2 plus CO2 methanogenesis was constitutive, while formate methanogenesis required adaptation time; selenium was necessary for formate utilization. Cells grown on formate had 20 to 100 times higher methanogenesis rates on formate than cells grown on H2-CO2 and transferred into formate medium. Enzyme assays with crude extracts and with F420 or methyl viologen as the electron acceptor revealed that hydrogenase was constitutive, while formate dehydrogenase was regulated. Cells grown on formate had 10 to 70 times higher formate dehydrogenase activity than cells grown on H2-CO2 with Se present in the medium; when no Se was added to H2-CO2 cultures, even lower activities were observed. Adaptation to and growth on formate were pH dependent, with an optimal pH for both about one pH unit above that optimal for H2-CO2 (pH 5.8 to 6.5). When cells were grown on H2-CO2 in the presence of formate, formate (greater than or equal to 50 mM) inhibited both growth and methanogenesis at pH 5.8 to 6.2, but not at pH greater than 6.6. Both acetate and propionate produced similar inhibition. Formate inhibition was also observed in Methanospirillum hungatei.

Acetates↗
PubMed1986

Source of carbon and hydrogen in methane produced from formate by Methanococcus thermolithotrophicus.

Methanococcus thermolithotrophicus is able to produce methane either from H2-CO2 or from formate. The route of formate entry into the methanogenic pathway was investigated by using 2H2O or [13C]formate and analysis by mass spectrometry. When cells (H2-CO2 or formate grown) were transferred to formate medium in 95% 2H water, the proportion of 2H in methane was 95%. When cells (H2-CO2 or formate grown) were transferred to media containing [13C]formate in the presence of H2-CO2 or He-CO2, the ratio of 13CH4 to 12CH4 increased over time parallel to the ratio of 13CO2 to 12CO2. The cells catalyzed a significant exchange of label between [13C]formate and 13CO2.

Carbon↗
PubMed1984

The bioenergetics of methanogenesis.

The reduction of CO2 or any other methanogenic substrate to methane serves the same function as the reduction of oxygen, nitrate or sulfate to more reduced products. These exergonic reactions are coupled to the production of usable energy generated through a charge separation and a protonmotive-force-driven ATPase. For the understanding of how methanogens derive energy from C-1 unit reduction one must study the biochemistry of the chemical reactions involved and how these are coupled to the production of a charge separation and subsequent electron transport phosphorylation. Data on methanogenesis by a variety of organisms indicates ubiquitous use of CH3-S-CoM as the final electron acceptor in the production of methane through the methyl CoM reductase and of 5-deazaflavin as a primary source of reducing equivalents. Three known enzymes serve as catalysts in the production of reduced 5-deazaflavin: hydrogenase, formate dehydrogenase and CO dehydrogenase. All three are potential candidates for proton pumps. In the organisms that must oxidize some of their substrate to obtain electrons for the reduction of another portion of the substrate to methane (e.g., those using formate, methanol or acetate), the latter two enzymes may operate in the oxidizing direction. CO2 is the most frequent substrate for methanogenesis but is the only substrate that obligately requires the presence of H2 and hydrogenase. Growth on methanol requires a B12-containing methanol-CoM methyl transferase and does not necessarily need any other methanogenic enzymes besides the methyl-CoM reductase system when hydrogenase is present. When bacteria grow on methanol alone it is not yet clear if they get their reducing equivalents from a reversal of methanogenic enzymes, thus oxidizing methyl groups to CO2. An alternative (since these and acetate-catabolizing methanogens possess cytochrome b) is electron transport and possible proton pumping via a cytochrome-containing electron transport chain. Several of the actual components of the methanogenic pathway from CO2 have been characterized. Methanofuran is apparently the first carbon-carrying cofactor in the pathway, forming carboxy-methanofuran. Formyl-FAF or formyl-methanopterin (YFC, a very rapidly labelled compound during 14C pulse labeling) has been implicated as an obligate intermediate in methanogenesis, since methanopterin or FAF is an essential component of the carbon dioxide reducing factor in dialyzed extract methanogenesis. FAF also carries the carbon at the methylene and methyl oxidation levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetates↗
PubMed1984

A method for the spectrophotometric assay of anaerobic enzymes.

A convenient and inexpensive system for conducting large numbers of spectrophotometric assays at wavelengths between 300 and 750 nm under strictly anaerobic conditions has been developed. Round test tubes or round cuvettes stoppered with either thick black rubber stoppers or thinner red rubber stoppers are used to replace rectangular cuvettes. The round tubes are held in place in the spectrophotometer by a simple metal holder. Additions to the tubes are made by syringe using a specially constructed needle guide to prevent needle bending.

Anaerobiosis↗
PubMed1983

A novel one-carbon carrier (carboxy-5,6,7,8-tetrahydromethanopterin) isolated from Methanobacterium thermoautotrophicum and derived from methanopterin.

During short-term labeling experiments, cells of Methanobacterium thermoautotrophicum incorporated a substantial part of 14CO2 in a compound with a bright yellow fluorescence on dry thin-layer chromatography plates and called yellow fluorescent compound (YFC) [Daniels, L. and Zeikus, J.G. (1978) J. Bacteriol. 136, 75-84]. This compound was extracted and purified by ion-exchange column chromatography with formic acid gradients up to 0.3 M. Out of 325 g wet cells of M. thermoautotrophicum about 4 mg of the compound were isolated. This material and some degradation products obtained from it were studied by means of chemical decomposition, ultraviolet-visible-light spectroscopy and preliminary 1H-NMR spectroscopy. It has structural elements in common with methanopterin (see preceding paper in this journal); these elements are a pterin group, glutamate, a hexosamine. The pterin in this compound is present in a reduced form, presumably as 5,6,7,8-tetrahydromethanopterin, and the additional one-carbon unit is probably present as a carboxy group. Probably the first step of methanogenesis implies a carboxylation of methanopterin and a concomitant reduction of the pterin. The trivial name carboxy-5,6,7,8-tetrahydromethanopterin is introduced for the compound.

Carbon↗
PubMed1983

Paramagnetic centers in the nickel-containing, deazaflavin-reducing hydrogenase from Methanobacterium thermoautotrophicum.

Two hydrogenases from the methanogenic bacterium Methanobacterium thermoautotrophicum strain DeltaH have been purified and contain tightly bound nickel as well as the anticipated iron/sulfur atoms with a fixed ratio of 15-20 iron atoms per nickel. One hydrogenase reduces the 8-hydroxy-5-deazaflavin coenzyme factor 420 (F(420)), whereas the other has been purified as a methyl viologen-reducing hydrogenase. Both enzymes possess an EPR signal attributed to paramagnetic nickel as demonstrated by hyperfine coupling in (61)Ni-containing hydrogenases. Comparison to model compounds suggests a nickel(III) oxidation state in the inactive forms of these aerobically purified enzymes. Loss of the nickel(III) signal accompanies reductive activation but is not kinetically correlated with regain of high specific activity. On replacement of H(2) by argon in the gas phase over reduced, active, F(420)-reducing enzyme, several EPR signals appear, including a signal at g = 2.004 that is probably enzyme-bound FADH semiquinone, two signals at g = 2.140 and 2.196 that reflect a new form of paramagnetic nickel(III), and also a signal at g = 2.036 that may be an iron signal. The F(420)-reducing hydrogenase in the second paramagnetic nickel form is either itself active or in facile equilibrium with active enzyme. The size of the signal at g = 2.036 may correlate with the degree of activation of the enzyme. In contrast to the hydrogenase of Clostridium pasteurianum [Erbes, D. L., Burris, R. H. & Orme-Johnson, W. H. (1975) Proc. Natl. Acad. Sci. USA 72, 4795-4799], which appears to use only iron/sulfur prosthetic groups and which reacts with one-electron-transfer agents, this methanogen hydrogenase seems to utilize iron, nickel, and flavin redox sites and to reduce obligate one-electron (viologen) and two-electron (deazaflavin) oxidants.

Coenzymes↗
PubMed1982

Purification and properties of an 8-hydroxy-5-deazaflavin-reducing hydrogenase from Methanobacterium thermoautotrophicum.

A coenzyme F430-reducing hydrogenase from Methanobacterium thermoautotrophicum has been purified 25-fold, to approximately 50% homogeneity. Following anaerobic preincubation in high salt under reducing conditions, the purified enzyme exhibits equal catalytic activity (turnover number = 725 s-1) toward the artificial 1-electron acceptor, methyl viologen, and the physiological 2-electron acceptor, 7,8-didemethyl-8-hydroxy-5-deazaflavin (F420). The enzyme had the following Km values (micromolarity) under the described assay conditions: 420 (methyl viologen, pH 9.0), 19 (F420, pH 7.2), 34 (Fo, 7.8-didemethyl-8-hydroxy-5-deazariboflavin, pH 7.2), 10 (H2, Fo as co-substrate, pH 7.2), 2 (H2, methyl viologen as co-substrate, pH 9.0). The native protein is oligomeric (apparent Mr greater than 500,000) and is composed of three distinct subunits with Mr - 40,000, 31,000, and 26,000 in the ratio of 2:2:1, leading to a minimum Mr = 170,000. In addition to 33 atoms of Fe and 24 atoms of acid-labile sulfur, the F420-hydrogenase contains 2.3 mol of FAD/mol of Mr - 170,000. This activity is chromatographically distinct from a smaller methanogen hydrogenase capable of rapid viologen reduction, but which only very slowly reduces 5-deazariboflavins.

Euryarchaeota↗
PubMed1980

Product isotope effects on in vivo methanogenesis by Methanobacterium thermoautotrophicum.

The hydrogen in methane produced by cultures of Methanobacterium thermoautotrophicum originates from water. In H2O/D2O mixtures, a methane product isotope effect is observed that increases rapidly as the water deuterium enrichment approaches 100%. This effect is due to the intracellular production of protons from H2, catalyzed by hydrogenase, which occurs at 12% the rate of water diffusion through the cell membrane. We estimate that water diffusion through the thick cell membrane of M. thermoautotrophicum is retarded by a factor of 10(6) over the free diffusion rate. The intracellular production of H+ suggests that either (1) hydrogenase is not directly involved in the production of a chemiosmotic proton gradient or (2) if it is involved, the proton gradient exists between the cytosol and the interior of vesicles observed in this bacterium. The intrinsic deutrium product isotope effect in methanogenesis is 1.20 +/- 0.1, comparable to anabolic deuterium product isotope effects in other autotrophs. An algebraic model incorporating the intracellular H2 to H+ flux accurately predicts the distribution of deuterated methane species at all levels of water deuterium enrichment.

Deuterium↗
PubMed1980

The obese child: observations in the gymnasium of the Adelaide Children's Hospital.

This study reviews 107 obese children who were referred to the gymnasium of the Adelaide Children's Hospital. The majority had multiple handicaps. The treatment involved physical activities in small groups associated with counselling of parents (both individually and in groups) by social workers, dietitians, and doctors. A significant number of children were helped by the programme, showing not only a reduction in weight but also improvement in behaviour and attitude. Some children exhibited a hypoactive form of minimal cerebral dysfunction, which is postulated as a new risk factor in the development of childhood obesity. The importance of prevention is emphasized.

Adolescent↗
PubMed1980

Origin of hydrogen in methane produced by Methanobacterium thermoautotrophicum.

The production of deuterated methane by Methanobacterium thermoautotrophicum in H2O-D2O mixtures was examined by high-resolution mass spectrometry. The hydrogen in the methane arose solely from water and not from hydrogen gas. Hydrogen gas served only as an electron source in methanogenesis. A whole-cell product isotope discrimination of 1.5 favoring hydrogen over deuterium was observed in methane production in 81 atom% deuterated water. The distribution of deuterated methane species is described by a simple model of the overall reaction.

Deuterium↗
PubMed1978

One-carbon metabolism in methanogenic bacteria: analysis of short-term fixation products of 14CO2 and 14CH3OH incorporated into whole cells.

Methanobacterium thermoautotrophicum, M. ruminantium, and Methanosarcina barkeri were labeled with 14CO2 (14CO2 + H14CO3- + 14CO32-) for from 2 to 45 s. Radioactivity was recovered in coenzyme M derivatives, alanine, aspartate, glutamate, and several unidentified compounds. The properties of one important structurally unidentified intermediate (yellow fluorescent compound) displayed UV absorbance maxima at pH 1 of 290 and 335 nm, no absorbance in the visible region, and a fluorescence maximum at 460 nm. Label did not appear in organic phosphates until after 1 min. 14CH3OH was converted by M. barkeri primarily into coenzyme M derivatives at 25 s. [2-14C]acetate was assimilated by M. thermoautotrophicum mainly into alanine and succinate during 2 to 240 s, but not into coenzyme M derivatives or yellow fluorescent compound. Cell-free extracts of M. thermoautotrophicum lacked ribulose 1,5-bisphosphate carboxylase activity. The data indicated the absence of the Calvin, serine, and hexulose phosphate paths of C1 assimilation in the methanogens examined and indicated that pyruvate was an early intermediate product of net CO2 fixation. The in vivo importance of coenzyme M derivatives in methanogenesis was demonstrated.

Alanine↗