Response of atmospheric methane consumption by maine forest soils to exogenous aluminum salts.
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Atmospheric methane consumption by Maine forest soils was inhibited by additions of environmentally relevant levels of aluminum. Aluminum chloride was more inhibitory than nitrate or sulfate salts, but its effect was comparable to that of a chelated form of aluminum. Inhibition could be explained in part by the lower soil pH values which resulted from aluminum addition. However, significantly greater inhibition by aluminum than by mineral acids at equivalent soil pH values indicated that inhibition also resulted from direct effects of aluminum per se. The extent of inhibition by exogenous aluminum increased with increasing methane concentration for soils incubated in vitro. At methane concentrations of >10 ppm, inhibition could be observed when aluminum chloride was added at concentrations as low as 10 nmol g (fresh weight) of soil(-1). These results suggest that widespread acidification of soils and aluminum mobilization due to acid precipitation may exacerbate inhibition of atmospheric methane consumption due to changes in other parameters and increase the contribution of methane to global warming. (+info)
Parallel processing of substrate correlates with greater functional stability in methanogenic bioreactor communities perturbed by glucose.
(50/1531)
Parallel processing is more stable than serial processing in many areas that employ interconnected activities. This hypothesis was tested for microbial community function using two quadruplicate sets of methanogenic communities, each set having substantially different populations. The two communities were maintained at a mean cell residence time of 16 days and a mean glucose loading rate of 0.34 g/liter-day in variable-volume reactors. To test stability to perturbation, they were subjected to an instantaneous glucose pulse that resulted in a 6.8-g/liter reactor concentration. The pattern of accumulated products in response to the perturbation was analyzed for various measures of functional stability, including resistance, resilience, and reactivity for each product. A new stability parameter, "moment of amplification envelope," was used to compare the soluble compound stability. These parameters indicated that the communities with predominantly parallel substrate processing were functionally more stable in response to the perturbation than the communities with predominantly serial substrate processing. The data also indicated that there was good replication of function under perturbed conditions; the degrees of replication were 0.79 and 0.83 for the two test communities. (+info)
Flexible community structure correlates with stable community function in methanogenic bioreactor communities perturbed by glucose.
(51/1531)
Methanogenic bioreactor communities were used as model ecosystems to evaluate the relationship between functional stability and community structure. Replicated methanogenic bioreactor communities with two different community structures were established. The effect of a substrate loading shock on population dynamics in each microbial community was examined by using morphological analysis, small-subunit (SSU) rRNA oligonucleotide probes, amplified ribosomal DNA (rDNA) restriction analysis (ARDRA), and partial sequencing of SSU rDNA clones. One set of replicated communities, designated the high-spirochete (HS) set, was characterized by good replicability, a high proportion of spiral and short thin rod morphotypes, a dominance of spirochete-related SSU rDNA genes, and a high percentage of Methanosarcina-related SSU rRNA. The second set of communities, designated the low-spirochete (LS) set, was characterized by incomplete replicability, higher morphotype diversity dominated by cocci, a predominance of Streptococcus-related and deeply branching Spirochaetales-related SSU rDNA genes, and a high percentage of Methanosaeta-related SSU rRNA. In the HS communities, glucose perturbation caused a dramatic shift in the relative abundance of fermentative bacteria, with temporary displacement of spirochete-related ribotypes by Eubacterium-related ribotypes, followed by a return to the preperturbation community structure. The LS communities were less perturbed, with Streptococcus-related organisms remaining prevalent after the glucose shock, although changes in the relative abundance of minor members were detected by morphotype analysis. A companion paper demonstrates that the more stable LS communities were less functionally stable than the HS communities (S. A. Hashsham, A. S. Fernandez, S. L. Dollhopf, F. B. Dazzo, R. F. Hickey, J. M. Tiedje, and C. S. Criddle, Appl. Environ. Microbiol. 66:4050-4057, 2000). (+info)
Starvation alters the apparent half-saturation constant for methane in the type II methanotroph Methylocystis strain LR1.
(52/1531)
When cells of a type II methanotrophic bacterium (Methylocystis strain LR1) were starved of methane, both the K(m(app)) and the V(max(app)) for methane decreased. The specific affinity (a(o)(s)) remained nearly constant. Therefore, the decreased K(m(app)) in starved cells was probably not an adjustment to better utilize low-methane concentrations. (+info)
Novel polyunsaturated n-alkenes in the marine diatom Rhizosolenia setigera.
(53/1531)
Four previously unknown n-C25 and n-C27 heptaenes of the marine diatom Rhizosolenia setigera were isolated and identified using NMR spectroscopy. They possess six methylene interrupted (Z)-double bonds starting at C-3 and an additional terminal or n-2 (Z)-double bond. Structural and stable carbon isotopic evidence suggests that these polyenes are biosynthesized by chain elongation of the C22:6n-3 fatty acid, followed by decarboxylation and introduction of double bonds at specific positions. (+info)
Possible interactions within a methanotrophic-heterotrophic groundwater community able to transform linear alkylbenzenesulfonates.
(54/1531)
The relationships and interactions within a methanotrophic-heterotrophic groundwater community were studied in a closed system (shake culture) in the presence of methane as the primary carbon and energy source and with the addition of the pure linear alkylbenzenesulfonate (LAS) congener 2-[4-(sulfophenyl)]decan as a cometabolic substrate. When cultured under different conditions, this community was shown to be a stable association, consisting of one obligate type II methanotroph and four or five heterotrophs possessing different nutritional and physiological characteristics. The results of experiments examining growth kinetics and nutritional relationships suggested that a number of complex interactions existed in the community in which the methanotroph was the only member able to grow on methane and to cometabolically initiate LAS transformation. These growth and metabolic activities of the methanotroph ensured the supply of a carbon source and specific nutrients which sustained the growth of four or five heterotrophs. In addition to the obligatory nutritional relationships between the methanotroph and heterotrophs, other possible interactions resulted in the modification of basic growth parameters of individual populations and a concerted metabolic attack on the complex LAS molecule. Most of these relationships conferred beneficial effects on the interacting populations, making the community adaptable to various environmental conditions and more efficient in LAS transformation than any of the individual populations alone. (+info)
alpha-methylene ordering of acyl chains differs in glucolipids and phosphatidylglycerol from Acholeplasma laidlawii membranes: (2)H-NMR quadrupole splittings from individual lipids in mixed bilayers.
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A Acholeplasma laidlawii strain A-EF22 was grown in a medium supplemented with alpha-deuterated oleic acid. Phosphatidylglycerol (PG), the glucolipids monoglucosyldiacylglycerol (MGlcDAG), diglucosyldiacylglycerol (DGlcDAG) and monoacyldiglucosyldiacylglycerol, and the phosphoglucolipid glycerophosphoryldiglucosyldiacylglycerol (GPDGlcDAG) were purified, and the phase behaviour and molecular ordering for the individual lipids, as well as for mixtures of the lipids, were studied by (2)H-, (31)P-NMR and X-ray scattering methods. The chemical structure of all the A. laidlawii lipids, except PG, has been determined and verified previously; here also the chemical structure of PG was verified, utilising mass spectrometry and (1)H and (13)C high resolution NMR spectroscopy. For the first time, lipid dimers were found in the mass spectrometry measurements. The major findings in this work are: (1) addition of 50 mol% of PG to the non-lamellar-forming lipid MGlcDAG does not significantly alter the transition temperature between lamellar and non-lamellar phases; (2) the (2)H-NMR quadrupole splitting patterns obtained from the lamellar liquid crystalline phase are markedly different for PG on one hand, and DGlcDAG and GPDGlcDAG on the other hand; and (3) mixtures of PG and DGlcDAG or MGlcDAG give rise to (2)H-NMR spectra consisting of a superposition of splitting patterns of the individual lipids. These remarkable features show that the local ordering of the alpha-carbon of the acyl chains is different for PG than for MGlcDAG and DGlcDAG, and that this difference is preserved when PG is mixed with the glucolipids. The results obtained are interpreted in terms of differences in molecular shape and hydrophilicity of the different polar headgroups. (+info)
Methanocalculus pumilus sp. nov., a heavy-metal-tolerant methanogen isolated from a waste-disposal site.
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A mesophilic hydrogenotrophic methanogen, strain MHT-1T, was isolated from the leachate of a sea-based site for solid waste disposal (the port of Osaka, Japan). Strain MHT-1T was found to be an irregular coccus and was able to use H2/CO2 and formate as energy sources. Acetate was required for growth. The optimum temperature and pH for growth were 35 degrees C and 6.5-7.5, respectively. Strain MHT-1T was resistant to high concentrations of several heavy metals such as CdCl2 and CuSO4. The G+C content of the DNA was 51.9 mol%. Analysis of the 16S rRNA gene revealed that the isolate was a member of the genus Methanocalculus but distinct from its nearest neighbour, Methanocalculus halotolerans, there being a sequence similarity of 98.9%. DNA-DNA hybridization analysis revealed 51% relatedness with the DNA of M. halotolerans strain SEBR 4845T. The optimum NaCl concentration was 1.0%, whereas the optimum in M. halotolerans was 5.0%. A new species, Methanocalculus pumilus, is proposed for strain MHT-1T. The type strain is MHT-1T (= DSM 12632T = JCM 10627T). (+info)