Poly[μ-4,4′-bipyridine-κ2 N:N′-μ-thio­cyanato-κ2 N:S-copper(I)]

In the crystal structure of the title compound, [Cu(NCS)(C10H8N2)]n, the CuI atom is coordinated by two N atoms from two symmetry-related 4,4′-bipyridine (bipy) ligands and one N and one S atom from two symmetry-related thio­cyanate ligands in a distorted tetra­hedral environment. The thio­cyanate ligands bridge the CuI atoms into a zigzag [CuSCN]n chain running parallel to the a axis. These chains are further connected through two bipy ligands that bridge the CuI centers to generate a two-dimensional brick-like network. The pyridyl planes of the ligands exhibit a dihedral angle of 37.35 (12)°

Di-μ-chlorido-bis­[bis­(ethyl­enediamine-κ2 N,N′)cadmium(II)] dichloride

The crystal structure of the title compound, [Cd2Cl2(C2H8N2)4]Cl2, consists of binuclear centrosymmetric [Cd2(C2H8N2)4Cl2]2+ cations and discrete chloride anions. The CdII cation is coordinated by four N atoms of two ethyl­enediamine ligands and two symmetry-related chloride anions within a distorted CdN4Cl2 octa­hedron. Two CdII cations are connected by two chloride anions via μ2-coordination, forming a four-membered Cd2Cl2 ring. The uncoordinated chloride anions are linked to the amino groups via N—H⋯Cl hydrogen bonding. Two C atoms of one of the two crystallographically independent ethyl­enediamine ligands are disordered and were refined using a split model [occupancy ratio 0.674 (9):0.326 (9)]

catena-Poly[bis­[cis-dipyrimidine-trans-dithio­cyanato­iron(II)]-di-μ-pyrimidine-[trans-dithio­cyanato­iron(II)]-di-μ-pyrimidine]

In the crystal structure of the title compound, [Fe3(NCS)6(C4H4N2)8]n, each iron(II) cation is coordinated by four N-bonded pyrimidine ligands and two N-bonded thio­cyanate anions in a distorted octa­hedral environment. The asymmetric unit consists of one iron cation located on a crystallographic center of inversion, as well as one iron cation, three thio­cyanate anions and four pyrimidine ligands occupying general positions. The structure consists of square secondary building units (SBUs) with an Fe atom at each corner, which are μ-N 1:N 3-bridged by the pyrimidine ligands. The SBUs are linked into infinite chains running in the c-axis direction via common opposite corners

Poly[bis­(cyanato-κN)bis­(μ-pyrazine-κ2 N:N′)cobalt(II)]

In the crystal structure of the title compound, [Co(NCO)2(C4H4N2)2]n, the Co(II) cation is coordinated by four N-bonded pyrazine ligands and two N-bonded cyanate anions in a slightly distorted octa­hedral geometry. The crystal structure consists of μ-N:N′ pyrazine-bridged cobalt cyanate chains; these are further linked by additional μ-N:N′-bridging pyrazine ligands into layers, which are stacked perpendicular to the crystallographic a axis. The C and O atoms in both crystallographic independent cyanate anions are disordered in two orientations and were refined using a split model with site occupation factor ratios of 0.75/0.25 and 0.7/0.3

Prevalence, antimicrobial resistance and genotyping (AFLP) of thermophilic Campylobacter spp. in broiler flocks and analysis of risk factors for Campylobacter colonisation at flock level

Titelblatt Persönlicher Dank Inhaltsverzeichnis Abkürzungsverzeichnis Einleitung Literaturübersicht Eigene Untersuchungen Ergebnisse Diskussion Schlussfolgerungen Zusammenfassung Summary Quellenverzeichnis Anhang Danksagung, Lebenslauf, SelbstständigkeitserklärungIm Zeitraum von Mai 2004 bis Juli 2005 wurden 279 Masthähnchenherden verschiedener Haltungssysteme auf das Vorkommen von thermophilen Campylobacter spp. beprobt. Hierzu wurde pro Herde der Blinddarmkot von zehn Tieren als Pool- und/oder Einzelproben untersucht. Alle gewonnenen Campylobacter- Isolate wurden durch eine Multiplex- PCR bestätigt. 79 Campylobacter- Isolate wurden durch Mikrodilution auf ihr Verhalten gegenüber acht Antibiotika (-Kombinationen) getestet, 236 Campylobacter- Isolate wurden mittels der AFLP- Analyse feintypisiert. Zuletzt wurden 75 Mastanlagen anhand eines Fragebogens auf mögliche Einflussfaktoren für den Campylobacter- Eintrag in die Herden untersucht. 44% der Herden waren Campylobacter- positiv. C. jejuni wurde mit 77% als dominierende Spezies detektiert, gefolgt von C. coli mit 23%. Das Vorkommen von Campylobacter spp. in den Masthähnchenherden war jahreszeitlichen Schwankung unterworfen mit hohen Prävalenzen in den warmen Sommer- und Herbstmonaten. Die Innerherdenprävalenz variierte von 10% bis 100%. Bei 33% der Herden waren alle zehn Blinddarmpaare positiv. Während in den Campylobacter- positiven Herden aus konventionellen und Louisiana- Ställen vor allem C. jejuni detektiert wurde, war in den Herden aus Freiland- und biologischer Haltung C. coli vorherrschend. Durch Untersuchung von Poolproben wurden 93% der durch Einzeluntersuchung als Campylobacter- positiv befundenen Herden erkannt. Von den 79 untersuchten Campylobacter- Isolaten waren 30% Ampicillin- resistent, 13% resistent gegen Ampicillin in Kombination mit Sulbactam, 10% Ceftazidim- resistent, 41% Ciprofloxacin- und Nalidixinsäure- resistent und 30% Tetrazyklin- resistent. Alle Isolate waren empfindlich gegenüber Gentamicin. Gegenüber Erythromycin waren alle C. jejuni- Isolate sensibel, wohingegen 28% der C. coli- Isolate resistent waren. Es wurden 34 Cluster für 61 C. jejuni- Isolate und 11 Cluster für 18 C. coli- Isolate identifiziert. Dies verdeutlicht die genetische Diversität von Campylobacter spp. bei Mastgeflügel. Das Vorfinden von dominierenden und wiederkehrenden AFLP- Genotypen in aufeinander folgenden Herden verdeutlicht das Bestehen von persistierenden Infektionsquellen in der Umwelt. Das Vorkommen von Campylobacter- negativen Herden nach Campylobacter- positiven Herden zeigt, dass eine Infektion der Herde verhindert werden kann. Die Präsens von verschiedenen Campylobacter- Spezies in einer Herde und in aufeinander folgenden Herden eines Stalles deutet auf verschiedene Infektionsquellen hin und beschreibt die Dynamik der Kolonisation. Anhand der Fragebogenaktion konnten drei Einflussfaktoren für eine Campylobacter- Belastung von Masthähnchenherden erkannt werden: die Haltungsform, die Herdengröße und die Tränkeform. Andere Variablen, wie Hygienemaßnahmen, Alter, Serviceperiode und Wasserquelle hatten keinen signifikanten Einfluss auf die Campylobacter- Prävalenz.From May 2004 to July 2005, 279 broiler flocks of different production types were tested for the presence of thermophilic Campylobacter spp. Of each flock caecal content of ten chickens was tested. All Campylobacter isolates were additionally identified by multiplex- PCR. 79 Campylobacter isolates were tested for susceptibility to eight antimicrobial agents and combinations by microbroth dilution and 236 Campylobacter isolates were genotyped by AFLP- analysis, too. To identify potential risk factors for the presence of Campylobacter spp. at flock level, 75 farms were analysed using farm and flock specific information obtained from questionnaires. Of all investigated broiler flocks Campylobacter spp. was detected in 44%. C. jejuni was the most prevalent species (77%) followed by C. coli (23%). Higher prevalence was mainly associated with summer and fall. Within- flock prevalence varied from 10% to 100%. In 33% of the Campylobacter positive flocks all ten caecal probes were positive. Flocks of conventional and Louisiana broiler houses harboured in most cases C. jejuni, whereas C. coli was the predominant species in flocks from free range or organic farming. Comparing results of pooled and single probes, 93% of Campylobacter positive single probes were detected using pooled probes. Of the 79 (61 C. jejuni, 18 C. coli) chicken isolates 30% (31% bzw. 28%) were ampicillin resistant, 13% (8% bzw. 28%) were resistant against a combination of ampicillin and sulbactam, 10% (8% bzw. 17%) were ceftazidime resistant, 41% (39% bzw. 44%) were ciprofloxacin and nalidixic acid resistant und 30% (30% bzw. 33%) were tetracycline resistant. All strains were susceptible against gentamicin. All C. jejuni strains were susceptible against erythromycin, whereas 28% of C. coli strains were resistant. From 61 C. jejuni- isolates and 18 C. coli isolates 34 AFLP- cluster respectively 11 AFLP- cluster were identified, demonstrating the genetic diversity of Campylobacter spp. isolated from poultry. Dominant and reiterating AFLP- genotypes in successive flocks show the presence of persistent sources of Campylobacter spp. in the environment. Colonisation with sporadic isolates was also found. Campylobacter negative flocks followed Campylobacter positive flocks demonstrating, that it is possible to prevent a Campylobacter infection. Different Campylobacter species within a flock and in successive flocks may be caused by different sources of infections and describe the dynamic of colonisation. Three risk factors for Campylobacter colonisation were identified: production system, flock size and water system

A comprehensive analysis of the importance of translation initiation factors for Haloferax volcanii applying deletion and conditional depletion mutants

Translation is an important step in gene expression. The initiation of translation is phylogenetically diverse, since currently five different initiation mechanisms are known. For bacteria the three initiation factors IF1 – IF3 are described in contrast to archaea and eukaryotes, which contain a considerably higher number of initiation factor genes. As eukaryotes and archaea use a non-overlapping set of initiation mechanisms, orthologous proteins of both domains do not necessarily fulfill the same function. The genome of Haloferax volcanii contains 14 annotated genes that encode (subunits of) initiation factors. To gain a comprehensive overview of the importance of these genes, it was attempted to construct single gene deletion mutants of all genes. In 9 cases single deletion mutants were successfully constructed, showing that the respective genes are not essential. In contrast, the genes encoding initiation factors aIF1, aIF2γ, aIF5A, aIF5B, and aIF6 were found to be essential. Factors aIF1A and aIF2β are encoded by two orthologous genes in H. volcanii. Attempts to generate double mutants failed in both cases, indicating that also these factors are essential. A translatome analysis of one of the single aIF2β deletion mutants revealed that the translational efficiency of the second ortholog was enhanced tenfold and thus the two proteins can replace one another. The phenotypes of the single deletion mutants also revealed that the two aIF1As and aIF2βs have redundant but not identical functions. Remarkably, the gene encoding aIF2α, a subunit of aIF2 involved in initiator tRNA binding, could be deleted. However, the mutant had a severe growth defect under all tested conditions. Conditional depletion mutants were generated for the five essential genes. The phenotypes of deletion mutants and conditional depletion mutants were compared to that of the wild-type under various conditions, and growth characteristics are discussed

Dibromido(di-2-pyridyl sulfide-κ2 N,N′)zinc(II)

The molecule of the title compound, [ZnBr2(C10H8N2S)], contains a six-membered chelate ring in a boat conformation in which the Zn atom is coordinated by two Br atoms and by the two pyridyl N atoms of a single di-2-pyridyl sulfide (dps) ligand within a slightly distorted tetra­hedron. The dihedral angle between the pyridine rings is 52.7 (1)°. As is usual for this type of complex, the sulfide group does not participate in the zinc coordination

[Bis(3-amino­prop­yl)amine-κ3 N,N′,N′′]bis­(thio­cyanato-κN)cobalt(II)

The asymmetric unit of the title compound, [Co(NCS)2(C6H17N3)], consists of one Co2+ cation, two thio­cyanate anions and one bis­(3-amino­prop­yl)amine ligand, all in general positions. The cobalt cation is coordinated by five N atoms of two terminal N-bonded thio­cyanate anions and one bis­(3-amino­prop­yl)amine ligand, defining a slightly distorted square-pyramidal coordination polyhedron. The mol­ecules are held together in the crystal by weak N—H⋯S inter­actions

A triclinic polymorph of poly[[bis­[μ-1,2-bis­(pyridin-4-yl)ethene-κ2 N:N′]bis­(thio­cyanato-κN)cobalt(II)] 1,2-bis­(pyridin-4-yl)ethene monosolvate]

In the crystal structure of the title compound, [Co(NCS)2(C12H10N2)2]·C12H10N2, the CoII cations are octa­hedrally coordinated by two terminally N-bonded thio­cyanate anions and four 1,2-bis­(pyridin-4-yl)ethene (bpe) ligands. The asymmetric unit consists of three crystallographically independent CoII cations, six thio­cyanate anions and six coordinating bpe ligands in general positions. Additionally, three non-coordin­ating bpe ligands are present in the asymmetric unit with two of them located on a center of inversion. The CoII cations are connected by the bpe ligands into layers parallel to the bc plane. The crystal investigated was non-merohedrically twinned, with a fractional contribution of 0.261 (2) for the minor domain