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At least 343 records · Page 19Linked to original sources
PubMed1992

Effects of topography on caesium-137 in montane peat soils and vegetation.

This study investigated the relationship between altitude and 137Cs fallout in soils and plants. The soils and plants, Calluna vulgaris, Erica cinerea and Molinia caerulea, were sampled across a transect of two valleys in north-western Ireland. The results provided evidence that greater 137Cs deposition to soils occurred at higher altitudes, and the data supported the findings of a previous investigation in the same area. A valley effect, whereby greater concentrations of 137Cs accumulated in plants on the lower altitudes of the valley floors, was shown to be significant. Deposition values for total 137Cs in soils were not correlated with plant concentrations, although a relationship between concentrations in C. vulgaris and M. caerulea was found to be statistically significant. No relationship was observed between the 137Cs from weapons fallout with that of Chernobyl origin in the 0-10 cm depth soils, although a significant correlation emerged between the same two components measured in C. vulgaris. The results suggest that existing definitions of concentration ratios and transfer factors are, for many reasons, inappropriate for studies of soil to plant transfer of 137Cs in peatland ecosystems.

Accidents↗
PubMed2003

Molecular diversity in the bacterial community and the fluorescent pseudomonads group in natural and chlorobenzoate-stressed peat-forest soil.

Bacterial community shifts in a soil microcosm spiked with 3-chlorobenzoate or 2,5-dichlorobenzoate were monitored. The V6-V8 variable regions of soil bacterial 16S rRNA and rDNA were amplified and separated by temperature gradient gel electrophoresis (TGGE) profiling. Culturing in the presence of 2.5 mM chlorinated benzoates suppressed 10 to 100 fold the total aerobic bacterial community but had no effect on the diversity within the group of fluorescent pseudomonads. In contrast, the uncultured bacterial community showed a decrease in the number of bands in the TGGE profiles of the chlorobenzoate-spiked treatments. Accordingly, the Shannon's diversity and equitability indices of these treatments reflected a decreasing trend in time. The approach allowed a direct assessment of community shifts upon contamination of soil.

Bacteria↗
PubMed2006

Membrane lipids of mesophilic anaerobic bacteria thriving in peats have typical archaeal traits.

The 16S ribosomal DNA based distinction between the bacterial and archaeal domains of life is strongly supported by the membrane lipid composition of the two domains; Bacteria generally contain dialkyl glycerol diester lipids, whereas Archaea produce isoprenoid dialkyl glycerol diether and membrane-spanning glycerol dialkyl glycerol tetraether (GDGT) lipids. Here we show that a new group of ecologically abundant membrane-spanning GDGT lipids, containing branched instead of isoprenoid carbon skeletons, are of a bacterial origin. This was revealed by examining the stereochemistry of the glycerol moieties of those branched tetraether membrane lipids, which was found to be the bacterial 1,2-di-O-alkyl-sn-glycerol stereoconfiguration and not the 2,3-di-O-alkyl-sn-glycerol stereoconfiguration as in archaeal membrane lipids. In addition, unequivocal evidence for the presence of cyclopentyl moieties in these bacterial membrane lipids was obtained by NMR. The biochemical traits of biosynthesis of tetraether membrane lipids and the formation of cyclopentyl moieties through internal cyclization, which were thought to be specific for the archaeal lineage of descent, thus also occur in the bacterial domain of life.

Archaea↗
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↗
PubMed1980

Denitrification in Low pH Spodosols and Peats Determined with the Acetylene Inhibition Method.

Potential denitrification rates were determined for predominantly acid (pH >/= 3.6) horizons of forestal, miry, and agricultural soils from 22 locations in southern Finland. The acetylene inhibition method was used with nitrate-amended water-logged soils incubated in an N(2) atmosphere containing 2.5 or 5% C(2)H(2). Complete inhibition of the reduction of N(2)O to N(2) was observed in 99.3% of the samples. The denitrification rates varied from 0.12 to 53.8 mug of N.cm.day. Correlation between denitrification rate and soil pH was highly significant: r = 0.84 on a volume basis, and r = 0.44 on a weight basis. Vegetation type and amount of soil organic matter had a minor or no effect, respectively. In spodosolized soils the rates were significantly higher for B horizons than for A horizons. These results show that denitrification can occur in acid soils.

Journal Article↗