Analytical techniques used to assess the environmental risk of contamination from polycyclic aromatic hydrocarbons (PAHs) typically consider only abiotic sample parameters. Supercritical fluid extraction and sorption enthalpy experiments previously suggested slow desorption rates for PAH compounds in two coal-contaminated floodplain soils. In this study, the actual PAH availability for aerobic soil microorganisms was tested in two series of soil-slurry experiments.
View Article and Find Full Text PDFIn this study we determined the composition and biogeochemistry of novel, brightly colored, white and orange microbial mats at the surface of a brine seep at the outer rim of the Chefren mud volcano. These mats were interspersed with one another, but their underlying sediment biogeochemistries differed considerably. Microscopy revealed that the white mats were granules composed of elemental S filaments, similar to those produced by the sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus.
View Article and Find Full Text PDFIn anoxic environments, the oxidation of organic compounds, such as BTEX fuel components, by dissimilatory Fe(III) reduction can generate reactive mineral-bound Fe(II) species, which in turn are able to reduce other classes of organic and inorganic groundwater contaminants. In this study, we designed and evaluated an anaerobic batch reactor that mimicks iron-reducing conditions to investigate the factors that favor the coupling of microbial toluene oxidation and abiotic reduction of nitroaromatic contaminants. We investigated the influence of different Fe(III)-bearing minerals and combinations thereof on the coupling of these two processes.
View Article and Find Full Text PDFMethods Enzymol
December 2005
In anoxic habitats, ferric iron oxides and humic acids are widespread, and ferric-iron- and humic-acid-reducing microorganisms presumably play an important role in the oxidation of organic matter. Representative strains of ferric-iron- or humic-acid-reducing bacteria were isolated from a wide range of freshwater or marine environments. Most of them are strict anaerobes, and facultatively anaerobic microorganisms reduce ferric iron oxides or humic acids only after oxygen has been consumed.
View Article and Find Full Text PDFGeobacter metallireducens and G. sulfurreducens have been classified as strictly anaerobic bacteria which grow and thrive in subsurface and sediment environments. Hopanoids are pentacyclic triterpenoid lipids and are important for bacterial membrane stability and functioning.
View Article and Find Full Text PDFAppl Environ Microbiol
October 2004
Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant. Ferric iron reduction via sulfur cycling was investigated in more detail with Sulfurospirillum deleyianum, which can utilize sulfur or thiosulfate as an electron acceptor. In the presence of cysteine (0.
View Article and Find Full Text PDFArch Microbiol
October 2004
Geobacter species such as G. bremensis, G. pelophilus, and G.
View Article and Find Full Text PDFFEMS Microbiol Lett
March 2003
Iron-reducing bacteria can transfer electrons to ferric iron oxides which are barely soluble at neutral pH, and electron-shuttling compounds or chelators are discussed to be involved in this process. Experiments using semipermeable membranes for separation of ferric iron-reducing bacteria from ferric iron oxides do not provide conclusive results in this respect. Here, we used ferrihydrite embedded in 1% agar to check for electron-shuttling compounds in pure and in enrichment cultures.
View Article and Find Full Text PDFInt J Syst Evol Microbiol
September 2001
Two strictly anaerobic, dissimilatory ferric-iron-reducing bacteria, strains Dfr1T and Dfr2T, were isolated from freshwater mud samples with ferrihydrite as electron acceptor. Both strains also grew by reducing Mn(IV), S0 and fumarate. Electron donors used by strains Dfr1T and Dfr2T for growth with ferric iron as electron acceptor included hydrogen, formate, acetate, pyruvate, succinate, fumarate and ethanol.
View Article and Find Full Text PDFAnaerobic dissimilatory ferric iron-reducing and ferrous iron-oxidizing bacteria gain energy through reduction or oxidation of iron minerals and presumably play an important role in catalyzing iron transformations in anoxic environments. Numerous ferric iron-reducing bacteria have been isolated from a great diversity of anoxic environments, including sediments, soils, deep terrestrial subsurfaces, and hot springs. In contrast, only few ferrous iron-oxidizing bacteria are known so far.
View Article and Find Full Text PDFTwo new strains of marine purple bacteria, N1T and N2T, were isolated from coastal sediment of the North Sea (Germany) with ferrous iron as the only electron donor for anoxygenic photosynthesis. The isolates are the first salt-dependent, ferrous-iron-oxidizing purple bacteria characterized so far. Analysis of 16S rRNA gene sequences revealed an affiliation with the genus Rhodovulum, which until now comprises only marine species.
View Article and Find Full Text PDFAppl Environ Microbiol
December 1998
Anaerobic, nitrate-dependent microbial oxidation of ferrous iron was recently recognized as a new type of metabolism. In order to study the occurrence of three novel groups of ferrous iron-oxidizing, nitrate-reducing bacteria (represented by strains BrG1, BrG2, and BrG3), 16S rRNA-targeted oligonucleotide probes were developed. In pure-culture experiments, these probes were shown to be suitable for fluorescent in situ hybridization, as well as for hybridization analysis of denaturing gradient gel electrophoresis (DGGE) patterns.
View Article and Find Full Text PDFSyst Appl Microbiol
August 1998
Ferric iron was produced anaerobically from ferrous iron through the metabolic activity of recently described ferrous iron-oxidizing, nitrate-reducing bacteria. It was identified as poorly crystallized 2-line ferrihydrite with a particle size of 1-2 nm. This biologically produced ferrihydrite was shown to be a suitable electron acceptor for dissimilatory ferric iron-reducing bacteria in freshwater enrichment cultures, and was completely reduced to the ferrous state; no magnetite formation occurred.
View Article and Find Full Text PDFEnrichment and pure cultures of nitrate-reducing bacteria were shown to grow anaerobically with ferrous iron as the only electron donor or as the additional electron donor in the presence of acetate. The newly observed bacterial process may significantly contribute to ferric iron formation in the suboxic zone of aquatic sediments.
View Article and Find Full Text PDFWe have analysed the developmental defects in Drosophila embryos lacking a gelsolin-related protein encoded by the gene flightless I. Such embryos have previously been reported to gastrulate abnormally. We now show that the most dramatic defects are seen earlier, in actin-dependent events during cellularisation of the syncytial blastoderm, a process with similarities to cytokinesis.
View Article and Find Full Text PDFWe have cloned the gene for Drosophila gelsolin. Two mRNAs are produced from this gene by differential splicing. The protein encoded by the longer mRNA has a signal peptide and its electrophoretic mobility when translated in vitro in the presence of microsomes is higher than when it is translated without microsomes.
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