排序方式: 共有115条查询结果,搜索用时 15 毫秒
41.
Petra Bombach Hans H. Richnow Matthias Kästner Anko Fischer 《Applied microbiology and biotechnology》2010,86(3):839-852
Considering the high costs and technical difficulties associated with conventional remediation strategies, in situ biodegradation
has become a promising approach for cleaning up contaminated aquifers. To verify if in situ biodegradation of organic contaminants
is taking place at a contaminated site and to determine if these processes are efficient enough to replace conventional cleanup
technologies, a comprehensive characterization of site-specific biodegradation processes is essential. In recent years, several
strategies including geochemical analyses, microbial and molecular methods, tracer tests, metabolite analysis, compound-specific
isotope analysis, and in situ microcosms have been developed to investigate the relevance of biodegradation processes for
cleaning up contaminated aquifers. In this review, we outline current approaches for the assessment of in situ biodegradation
and discuss their potential and limitations. We also discuss the benefits of research strategies combining complementary methods
to gain a more comprehensive understanding of the complex hydrogeological and microbial interactions governing contaminant
biodegradation in the field. 相似文献
42.
Stable carbon isotope fractionation during degradation of dichloromethane by methylotrophic bacteria 总被引:2,自引:0,他引:2
Stable carbon isotope fractionation during dichloromethane (DCM) degradation by methylotrophic bacteria was investigated under aerobic and nitrate-reducing conditions. The strains studied comprise several Hyphomicrobium strains, Methylobacterium, Methylopila, Methylophilus and Methylorhabdus spp. that are considered to degrade DCM by a glutathione (GSH)-dependent dehalogenase enzyme system in the initial step. The stable carbon isotope fractionation factors (alphaC) of the strains varied under aerobic conditions between 1.043 and 1.071 and under nitrate-reducing conditions between 1.048 and 1.065. Comparison of isotope fractionation under aerobic and nitrate-reducing conditions by individual strains revealed only minor to no differences. The variability in isotope fractionation among strains was found to be related to the polymorphism of the functional genes encoding the DCM dehalogenase. 相似文献
43.
Tunneling nanotubes (TNTs) are nanoscaled, F-actin containing membrane tubes that connect cells over several cell diameters. They facilitate the intercellular exchange of diverse components ranging from small molecules to organelles and pathogens. In conjunction with recent findings that TNT-like structures exist in tissue, they are expected to have important implications in cell-to-cell communication. In this review we will focus on a new function of TNTs, namely the transfer of electrical signals between remote cells. This electrical coupling is not only determined by the biophysical properties of the TNT, but depends on the presence of connexons interposed at the membrane interface between TNT and the connected cell. Specific features of this coupling are compared to conventional gap junction communication. Finally, we will discuss possible down-stream signaling pathways of this electrical coupling in the recipient cells and their putative effects on different physiological activities. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics. 相似文献
44.
Jehmlich N Schmidt F Taubert M Seifert J Bastida F von Bergen M Richnow HH Vogt C 《Nature protocols》2010,5(12):1957-1966
We describe a stable isotope probing (SIP) technique that was developed to link microbe-specific metabolic function to phylogenetic information. Carbon ((13)C)- or nitrogen ((15)N)-labeled substrates (typically with >98% heavy label) were used in cultivation experiments and the heavy isotope incorporation into proteins (protein-SIP) on growth was determined. The amount of incorporation provides a measure for assimilation of a substrate, and the sequence information from peptide analysis obtained by mass spectrometry delivers phylogenetic information about the microorganisms responsible for the metabolism of the particular substrate. In this article, we provide guidelines for incubating microbial cultures with labeled substrates and a protocol for protein-SIP. The protocol guides readers through the proteomics pipeline, including protein extraction, gel-free and gel-based protein separation, the subsequent mass spectrometric analysis of peptides and the calculation of the incorporation of stable isotopes into peptides. Extraction of proteins and the mass fingerprint measurements of unlabeled and labeled fractions can be performed in 2-3 d. 相似文献
45.
Tanja K?gel Rüdiger Rudolf Erlend Hodneland John Copier Romano Regazzi Sharon A. Tooze Hans-Hermann Gerdes 《PloS one》2013,8(3)
Neuropeptide- and hormone-containing secretory granules (SGs) are synthesized at the trans-Golgi network (TGN) as immature secretory granules (ISGs) and complete their maturation in the F-actin-rich cell cortex. This maturation process is characterized by acidification-dependent processing of cargo proteins, condensation of the SG matrix and removal of membrane and proteins not destined to mature secretory granules (MSGs). Here we addressed a potential role of Rab3 isoforms in these maturation steps by expressing their nucleotide-binding deficient mutants in PC12 cells. Our data show that the presence of Rab3D(N135I) decreases the restriction of maturing SGs to the F-actin-rich cell cortex, blocks the removal of the endoprotease furin from SGs and impedes the processing of the luminal SG protein secretogranin II. This strongly suggests that Rab3D is implicated in the subcellular localization and maturation of ISGs. 相似文献
46.
Alexander Poser Regina Lohmayer Carsten Vogt Kay Knoeller Britta Planer-Friedrich Dimitry Sorokin Hans-H. Richnow Kai Finster 《Extremophiles : life under extreme conditions》2013,17(6):1003-1012
Microbial disproportionation of elemental sulfur to sulfide and sulfate is a poorly characterized part of the anoxic sulfur cycle. So far, only a few bacterial strains have been described that can couple this reaction to cell growth. Continuous removal of the produced sulfide, for instance by oxidation and/or precipitation with metal ions such as iron, is essential to keep the reaction exergonic. Hitherto, the process has exclusively been reported for neutrophilic anaerobic bacteria. Here, we report for the first time disproportionation of elemental sulfur by three pure cultures of haloalkaliphilic bacteria isolated from soda lakes: the Deltaproteobacteria Desulfurivibrio alkaliphilus and Desulfurivibrio sp. AMeS2, and a member of the Clostridia, Dethiobacter alkaliphilus. All cultures grew in saline media at pH 10 by sulfur disproportionation in the absence of metals as sulfide scavengers. Our data indicate that polysulfides are the dominant sulfur species under highly alkaline conditions and that they might be disproportionated. Furthermore, we report the first organism (Dt. alkaliphilus) from the class Clostridia that is able to grow by sulfur disproportionation. 相似文献
47.
Jechalke S Rosell M Martínez-Lavanchy PM Pérez-Leiva P Rohwerder T Vogt C Richnow HH 《Applied and environmental microbiology》2011,77(3):1086-1096
Multidimensional compound-specific stable isotope analysis (CSIA) was applied in combination with RNA-based molecular tools to characterize methyl tertiary (tert-) butyl ether (MTBE) degradation mechanisms occurring in biofilms in an aerated treatment pond used for remediation of MTBE-contaminated groundwater. The main pathway for MTBE oxidation was elucidated by linking the low-level stable isotope fractionation (mean carbon isotopic enrichment factor [ε(C)] of -0.37‰ ± 0.05‰ and no significant hydrogen isotopic enrichment factor [ε(H)]) observed in microcosm experiments to expression of the ethB gene encoding a cytochrome P450 monooxygenase able to catalyze the oxidation of MTBE in biofilm samples both from the microcosms and directly from the ponds. 16S rRNA-specific primers revealed the presence of a sequence 100% identical to that of Methylibium petroleiphilum PM1, a well-characterized MTBE degrader. However, neither expression of the mdpA genes encoding the alkane hydroxylase-like enzyme responsible for MTBE oxidation in this strain nor the related MTBE isotope fractionation pattern produced by PM1 could be detected, suggesting that this enzyme was not active in this system. Additionally, observed low inverse fractionation of carbon (ε(C) of +0.11‰ ± 0.03‰) and low fractionation of hydrogen (ε(H) of -5‰ ± 1‰) in laboratory experiments simulating MTBE stripping from an open surface water body suggest that the application of CSIA in field investigations to detect biodegradation may lead to false-negative results when volatilization effects coincide with the activity of low-fractionating enzymes. As shown in this study, complementary examination of expression of specific catabolic genes can be used as additional direct evidence for microbial degradation activity and may overcome this problem. 相似文献
48.
To explore the reliability of assays that detect aromatic-compound-degrading anaerobes, a combination of three functional-gene-targeting assays was applied to microcosms from benzene-contaminated aquifers. Results of the assays were consistent and suggest that species related to the genera Azoarcus and Geobacter dominated benzene degradation at the individual sites. 相似文献
49.
Martínez-Lavanchy PM Dohrmann AB Imfeld G Trescher K Tebbe CC Richnow HH Nijenhuis I 《Biodegradation》2011,22(5):973-982
Cultivation-independent analyses were applied to study the structural diversity of the bacterial community which developed
in groundwater inoculated microcosms actively metabolizing monochlorobenzene (MCB) under anaerobic conditions. Addition of
13C-labelled MCB demonstrated that the community produced 13CO2 as a metabolite at slightly increasing rates over a period of 1,051 days while no 13C-methane evolved. Genetic profiles of partial 16S rRNA genes generated with the single-strand conformation polymorphism (SSCP)
technique by PCR from directly extracted total DNA revealed that, despite the long incubation period, six replicate microcosms
were characterized by almost the same microbial members. Nine distinguishable contributors to the SSCP-profiles were characterized
by DNA sequencing, revealing the presence of different members from the phyla Proteobacteria, Fibrobacteres and from the candidate division OD1. DNA-stable isotope probing (SIP) was applied to distinguish the actual MCB metabolizing
bacteria from the other community members. This study reveals for the first time the structural diversity of an anaerobic
MCB metabolizing bacterial community. However, it also demonstrates the limitations of SIP to detect bacteria slowly metabolizing
carbon sources under anaerobic conditions. 相似文献
50.
Martin Taubert Carsten Vogt Tesfaye Wubet Sabine Kleinsteuber Mika T Tarkka Hauke Harms Fran?ois Buscot Hans-Hermann Richnow Martin von Bergen Jana Seifert 《The ISME journal》2012,6(12):2291-2301
Benzene is a major contaminant in various environments, but the mechanisms behind its biodegradation under strictly anoxic conditions are not yet entirely clear. Here we analyzed a benzene-degrading, sulfate-reducing enrichment culture originating from a benzene-contaminated aquifer by a metagenome-based functional metaproteomic approach, using protein-based stable isotope probing (protein-SIP). The time-resolved, quantitative analysis of carbon fluxes within the community supplied with either 13C-labeled benzene or 13C-labeled carbonate yielded different functional groups of organisms, with their peptides showing specific time dependencies of 13C relative isotope abundance indicating different carbon utilization. Through a detailed analysis of the mass spectrometric (MS) data, it was possible to quantify the utilization of the initial carbon source and the metabolic intermediates. The functional groups were affiliated to Clostridiales, Deltaproteobacteria and Bacteroidetes/Chlorobi. The Clostridiales-related organisms were involved in benzene degradation, putatively by fermentation, and additionally used significant amounts of carbonate as a carbon source. The other groups of organisms were found to perform diverse functions, with Deltaproteobacteria degrading fermentation products and Bacteroidetes/Chlorobi being putative scavengers feeding on dead cells. A functional classification of identified proteins supported this allocation and gave further insights into the metabolic pathways and the interactions between the community members. This example shows how protein-SIP can be applied to obtain temporal and phylogenetic information about functional interdependencies within microbial communities. 相似文献