Verbreitung und Diversität denitrifizierender Bakterien im Oberflächenwasser und hyporheischen Interstitial der Lahn unter dem Einfluß von Kläranlagenabwässern

Ziel dieser Arbeit war es, den Einfluß von eingeleitetem Klärwasser auf die Verbreitung und Diversität von denitrifizierenden Bakterien im Oberflächenwasser und hyporheischen Interstitial der Lahn zu untersuchen und mögliche Veränderungen sowie deren Ursachen zu detektieren. In den Jahren 1999 bis 2001 wurden aus dem Klär- und Oberflächenwasser und mit Hilfe von Multilevelsonden simultan aus unterschiedlichen Sedimenttiefen der Lahn (5, 15, 25 und 45 cm) Wasserproben entnommen. Die elektrische Leitfähigkeit weist auf einen starken Austausch zwischen Oberflächen- und Interstitialwasser bis in 45 cm Sedimenttiefe und auf einen geringen Einstrom des Grundwassers in die untersuchten Sedimentschichten hin. Für die untersuchten Interstitialbereiche stellt die Verfügbarkeit von Nitrat für die Denitrifikation keinen limitierenden Faktor dar. Eine Determinierung der Verbreitung von kultivierbaren denitrifizierenden Bakterien im Interstitial durch die Nitratkonzentration und bezüglich der Sedimenttiefe wurde nicht festgestellt. Auch ein temporär erhöhter Eintrag von Nitrat durch das Klärwasser führte weder zu einer deutlich erhöhten Nitratkonzentration noch zu einer erhöhten Denitratationspotenz in den flußabwärts des Kläranlagenablaufes gelegenen Interstitialbereichen. Eine schon aus vorangegangenen Projekten festgestellten Nitritanreicherungen konnten in dieser Untersuchung für den flußabwärts des Kläranlagenablaufes gelegenen Interstitialbereich in den Sommermonaten bestätigt werden. Aufgrund niedriger Ammoniumkonzentrationen und Denitratationspotenzen lassen sich diese nicht auf eine unvollständige Denitrifikation, sondern auf eine unvollständige Nitrifikation zurückführen. Im ca. 250 m flußabwärts vom Kläranlagenablauf gelegenen Interstitialbereich konnte keine Nitritakkumulation, dafür aber eine erhöhte Denitratationspotenz festgestellt werden. Da mit gesunkener Ammoniumkonzentration im Klärwasser die Denitratationspotenz in diesem Interstitialbereich erniedrigt war, weist dies auf eine scheinbar effektive Kopplung von Nitrifikation und Denitrifikation während erhöhter Ammoniumkonzentrationen hin. Im untersuchten Exfiltrationsbereich konnten vermehrt denitrifizierende Bakterien isoliert werden, so daß von einer Verbreitungspräferenz der kultivierbaren denitrifizierenden Bakterien im upwelling Bereich aufgrund der erniedrigten Sauerstoffkonzentration ausgegangen wird. Aufgrund von Tag-Nachtschwankungen der Sauerstoffkonzentration in der fließenden Welle und der gemessenen Differenz zwischen fließender Welle und Interstitialwasser ist von alternierenden Sauerstoffkonzentrationen im Interstitial und der Ausbildung von „anoxic sites“ in der Lahn auszugehen, wodurch eine Denitrifikation begünstigt wird. Die isolierten denitrifizierenden Bakterien wurden mittels der molekulargenetischen ARDRA-Methode in 24 phylogenetisch unterschiedliche Gruppen eingeteilt. Diese genotypische Diversität ist vergleichbar mit der von kultivierbaren Bakterien in Böden, die durch dieselbe Methode festgestellt wurde. Stämme der Gattungen Pseudomonas, Enterobacter, Bacillus, Aeromonas, Shewanella, Stenotrophomonas und Klebsiella wiesen eine vom Klärwasser unbeeinflußte Verbreitung auf. Sie gehören demnach der permanenten mikrobiellen Denitrifikantenpopulation im Oberflächen- und Interstitialwasser der Lahn an. Für die isolierten denitrifizierenden Stämme der Gattungen Pseudomonas und Bacillus konnte in dieser Untersuchung eine Persistenz im hyporheischen Interstitial der Lahn über einen Zeitraum von mindestens fünf Jahren festgestellt werden. Eine weite Verbreitung im Oberflächen- und Interstitialwasser der Lahn wies das Gram positive Bakterium Bacillus cereus und das Gram negative Bakterium Pseudomonas fluorescens auf, wobei letzteres in der kultivierbaren denitrifizierenden Bakterienpopulation dominiert. Im Gegensatz dazu wurden Ochrobactrum anthropi und Serratia spec. nur flußaufwärts im Oberflächenwasser detektiert, was auf eine Belastung der Lahn durch flußaufwärts gelegene punktuelle und diffuse Quellen hinweist. Während Alcaligenes Spezies und Acinetobacter spec. auf die Bedingungen im Klärwasser angewiesen sind, wurden Comamonadaceae nicht nur im Klärwasser nachgewiesen, sondern persistierend im Oberflächen- und Interstitialwasser der Lahn festgestellt. Die Veränderung innerhalb der kultivierbaren Bakterienpopulation der Lahn durch den Eintrag des Klärwassers zeigt sich insbesondere durch die restriktive Isolierung der Stämme der Comamonadaceae, die nur im und flußabwärts des Kläranlagenablaufes detektiert wurden. Eine direkte Einschwemmung dieser denitrifizierenden Bakterien durch das Klärwasser in das Interstitial der Lahn und eine Persistenz dieser im Interstitial konnte damit nachgewiesen werden

Genetic analysis and phenotypic characterization of three novel genes of Rhizobium tropici CIAT899 involved in symbiotic interactions with Phaseolus vulgaris

Rhizobium tropici CIAT899 is highly tolerant to many environmental stresses and a good competitor for nodule occupancy of Phaseolus vulgaris. Random transposon mutagenesis was performed with the aim to identify novel genes of this strain involved in symbiosis and stress tolerance. The analysis of the locus disrupted by the Tn5 insertion in mutants 899-PV9 and 899-PV4 led the discovery of three novel genes required for and efficient symbiotic interaction with beans plants. The first gene (syc1) bears significant similarity to voltage-gated chloride channels. A non-polar deletion in this gene caused serious deficiencies for nodule establishment, nodulation competitiveness and N2 fixation, probably due to its reduced ability to invade plant cells and to form stable symbiosomes, as judged by electron transmission microscopy. A second gene (olsC) found downstream of the former was shown to be homologous with aspartyl/asparaginyl β-hydroxylases and involved in the modification of two species of ornithine-containing lipids, presumably by a hydroxylation. A mutant carrying a non-polar deletion in olsC was symbiotically defective, whereas over-expressed OlsC in the complemented strain was related with an acid-sensitive phenotype. The third gene (sigE) codes for a putative σE factor. Analysis performed on the mutant carrying a deletion in this gene also revealed serious deficiencies for nodule development, nodulation competitiveness and N2 fixation when inoculated on bean plants. These three different bacterial activities have not been previously reported as required for the symbiotic interaction of rhizobia with its legume host

Improvement of common bean (Phaseolus vulgaris) nodulation by selected rhizobial strain from Egyptian soils through genotypic characterization, symbiotic effectiveness and competitiveness under salt stress conditions

To maximize the symbiotic nitrogen fixation of common bean (Phaseolus vulgaris) under egyptian soil conditions, twelve rhizobial isolates were isolated from root nodulated common bean. These isolates were physiologiacl characterized to test the more effeicient strains in nitrogen fixation, to select strains more adapted to environmetal stresses such as salinity, alkalinity, temperature. The adapted strains were selected to study the competitiveness of these strains against the standard strain CIAT 899 marked with gus gene under normal conditions, stress of salinity and stress of alkalinity. These strains were also characterized using molecular biology techniques such as REP-PCR, ARDRA of 16S and 23S rDNA, plasmid profiles analysis, sequencing of full length of 16S rDNA, hybridization with nifH gene and amplification of nodC gene. Strain EBRI 26 and Sinorhizobium meliloti strain 2010 were selected as salt tolerant strains to study the proteins involeved in salt tolerance by 2D proteom analysis and MALDI-Tof mass spectrometry

Verification of functional a posteriori error estimates for obstacle problem in 1D

We verify functional a posteriori error estimate for obstacle problem proposed by Repin. Simplification into 1D allows for the construction of a nonlinear benchmark for which an exact solution of the obstacle problem can be derived. Quality of a numerical approximation obtained by the finite element method is compared with the exact solution and the error of approximation is bounded from above by a majorant error estimate. The sharpness of the majorant error estimate is discussed.Web of Science49575473

Vapor Pressure of Ionic Liquids

We argue that the extremely low vapor pressures of room temperature ionic liquids near their triple points are due to the combination of strong ionic characters and of low melting temperatures.Comment: Initially submitted manuscript of article M. Bier and S. Dietrich, Mol. Phys. 108, 211 (2010) [Corrigendum: Mol. Phys. 108, 1413 (2010)

Acute Ethanol Effects on Focal Cerebral Ischemia in Nonfasted Rats

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66417/1/j.1530-0277.1997.tb03832.x.pd

Analyzing the Impacts of Off-Road Vehicle (ORV) Trails on Watershed Processes in Wrangell-St. Elias National Park and Preserve, Alaska

Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers

The Chop Gene Contains an Element for the Positive Regulation of the Mitochondrial Unfolded Protein Response

We have previously reported on the discovery of a mitochondrial specific unfolded protein response (mtUPR) in mammalian cells, in which the accumulation of unfolded protein within the mitochondrial matrix results in the transcriptional activation of nuclear genes encoding mitochondrial stress proteins such as chaperonin 60, chaperonin 10, mtDnaJ, and ClpP, but not those encoding stress proteins of the endoplasmic reticulum (ER) or the cytosol. Analysis of the chaperonin 60/10 bidirectional promoter showed that the CHOP element was required for the mtUPR and that the transcription of the chop gene is activated by mtUPR. In order to investigate the role of CHOP in the mtUPR, we carried out a deletion analysis of the chop promoter. This revealed that the transcriptional activation of the chop gene by mtUPR is through an AP-1 (activator protein-1) element. This site lies alongside an ERSE element through which chop transcription is activated in response to the ER stress response (erUPR). Thus CHOP can be induced separately in response to 2 different stress response pathways. We also discuss the potential signal pathway between mitochondria and the nucleus for the mtUPR

Systematic discovery of unannotated genes in 11 yeast species using a database of orthologous genomic segments

<p>Abstract</p> <p>Background</p> <p>In standard BLAST searches, no information other than the sequences of the query and the database entries is considered. However, in situations where two genes from different species have only borderline similarity in a BLAST search, the discovery that the genes are located within a region of conserved gene order (synteny) can provide additional evidence that they are orthologs. Thus, for interpreting borderline search results, it would be useful to know whether the syntenic context of a database hit is similar to that of the query. This principle has often been used in investigations of particular genes or genomic regions, but to our knowledge it has never been implemented systematically.</p> <p>Results</p> <p>We made use of the synteny information contained in the Yeast Gene Order Browser database for 11 yeast species to carry out a systematic search for protein-coding genes that were overlooked in the original annotations of one or more yeast genomes but which are syntenic with their orthologs. Such genes tend to have been overlooked because they are short, highly divergent, or contain introns. The key features of our software - called SearchDOGS - are that the database entries are classified into sets of genomic segments that are already known to be orthologous, and that very weak BLAST hits are retained for further analysis if their genomic location is similar to that of the query. Using SearchDOGS we identified 595 additional protein-coding genes among the 11 yeast species, including two new genes in <it>Saccharomyces cerevisiae</it>. We found additional genes for the mating pheromone a-factor in six species including <it>Kluyveromyces lactis</it>.</p> <p>Conclusions</p> <p>SearchDOGS has proven highly successful for identifying overlooked genes in the yeast genomes. We anticipate that our approach can be adapted for study of further groups of species, such as bacterial genomes. More generally, the concept of doing sequence similarity searches against databases to which external information has been added may prove useful in other settings.</p