Ecophysiological investigation of nitrite-oxidizing bacteria of the genus Nitrospira

Nitritoxidierende Bakterien (NOB) führen den zweiten Schritt der Nitrifikation, die Oxidation von Nitrit zu Nitrat durch, welcher von dem membranassozierten Enzym der NOB, der Nitritoxidoreduktase (Nxr) katalysiert wird. Die Nxr besteht aus mindestens zwei Untereinheiten, der nitritoxidierenden α-Unterheit und der kleineren β-Untereinheit, welche vom nxrAB-Operon kodiert werden. Der Hauptaugenmerk dieser Studie lag auf der ökophysiologischen Untersuchung von NOB des Genus Nitrospira in unterschiedlichen Habitaten. In dieser Studie wurde das Schüsselenzym der Nitritoxidation, die Nxr, auf unterschiedlichen Ebenen –auf RNA-, DNA- und Proteinebene – analysiert. Es wurde eine heterologe Expression des nxrAB-Operon, sowie des nxrA Genes des Candidatus Nitrospira defluvii durchgeführt, die zur Bildung von Proteinaggregaten führte. Weiters wurde das Potential des nxrA-Gens, welches die Nxr α-Untereinheit kodiert, als Marker für die Phylogenie innerhalb des Genus Nitrospira untersucht. Durch den Einsatz von nxrA als neues mögliches phylogenetisches Marker-Gen konnten Vertreter der Nitrospira sublineage I, die als typische Kläranlagenorganismen gelten, in Boden aufgefunden werden. Weiters wurde die bakterielle Diversität innerhalb einer vereinzelten Klärschlammflocke mit Hilfe der Kombination zweier Methoden, FISH gekoppelt an Mikromanipulation, erforscht. Im letzten Teil dieser Arbeit wurde Klärschlamm inkubiert, um eine Anreicherung von Nitrospira sublineage II Organismen zu erreichen. Allerdings führte diese Inkubation zu keiner erfolgreichen Anreicherung von Nitrospira sublineage II. Zusammengefasst zeigen die Ergebnisse dieser Arbeit die Notwendigkeit zukünftiger Untersuchungen, um weitere Einblicke in die Ökophysiologie dieser langsam wachsenden Bakteriengruppe zu erhalten, mit dem Ziel, Klärprozesse weiter optimieren zu können.The oxidation of nitrite to nitrate, is performed by nitrite-oxidizing bacteria (NOB). This oxidation is catalyzed by the membrane-associated enzyme nitrite oxidoreductase (Nxr), which consists at least two subunits, the large α-subunit and the small β-subunit, encoded by the nxrAB gene operon. The focus of this study lies on the ecophysiological investigation of NOB of the genus Nitrospira in various environments. In this thesis the key enzyme of nitrite oxidation, Nxr, was investigated on protein-, on DNA- and RNA-level, by heterologous expression of the nxrAB operon as well as the nxrA gene alone, by investigation of the potential of the nxrA gene as phylogenetic and functional maker gene of the genus Nitrospira, by micromanipulation of activated sludge flocs for bacterial diversity studies and by enrichment of Nitrospira sublineage II. The heterologous expression of both the nxrAB operon and the nxrA gene led to the formation of inclusion bodies. Expression analysis of the two copies of nxrA in the Nitrospira sublineage I genomes in the main WWTP of Vienna showed that only one of these gene duplicates was expressed during the sampling time point. Although former studies showed that Nitrospira sublineage II seems to be better adopted to low-nitrite concentrations than sublineage I, the incubation experiment in this study did not lead to a successful enrichment of members of Nitrospira sublineage II. All these results show that prospective studies are needed to gain more insights into the ecophysiology of these slow-growing organisms to be able to optimize wastewater treatment processes

High power 946nm Nd:YAG laser, longitudinally-pumped by a diode bar

We report efficient quasi-three-level operation of a Nd:YAG laser at 946nm pumped by a 20W diode bar. An output power of ~2.6W has been obtained for 14.4W of incident pump power

Efficient room temperature cw Yb:glass laser pumped by a 946nm Nd:YAG laser

By pumping with a cw diode-pumped Nd:YAG laser operating at 946nm laser operation of a new Yb-doped phosphate glass with 440mW cw output power and a slope efficiency of 48% with respect to the absorbed pump power was achieved at room temperature

Fachbericht Ökobilanzen von Wärmeerzeugern mit Leistungen von 50 kW bis 500 kW

DOI: http://dx.doi.org/10.13154/RUB.72.78 Der Fachbericht umfasst eine Recherche und Gegenüberstellung des Kumulierten Energieaufwands (KEA) und der Treibhausgas-Emissionen der Herstellung, Nutzung und Entsorgung von Heizkesseln in einem Leistungsbereich von 50 kW bis 500 kW. Grundlage für die Gegenüberstellung der Daten bildet ein Vergleich von Annahmen und Systemgrenzen unterschiedlicher verwendeter Ökobilanz-Datenbanken. Wettbewerb "Energieeffiziente Stadt" Website: https://www.wettbewerb-energieeffiziente-stadt.de/ Ruhr-Universität Bochum, Lehrstuhl Energiesysteme und Energiewirtschafthttp://www.lee.ruhr-uni-bochum.de

Towards a More Comprehensive Picture of the MicroRNA-23a/b-3p Impact on Impaired Male Fertility

The expression levels of various genes involved in human spermatogenesis are influenced by microRNAs (miRNAs), specifically microRNA-23a/b-3p. While certain genes are essential for spermatogenesis and male germ cell function, the regulation of their expression remains unclear. This study aimed to investigate whether microRNA-23a/b-3p targets genes involved in spermatogenesis and the impact of this targeting on the expression levels of these genes in males with impaired fertility. In-silico prediction and dual-luciferase assays were used to determine the potential connections between microRNA-23a/b-3p overexpression and reduced expression levels of 16 target genes. Reverse transcription-quantitative PCR (RT-qPCR) was conducted on 41 oligoasthenozoospermic men receiving infertility treatment and 41 age-matched normozoospermic individuals to verify the lower expression level of target genes. By employing dual-luciferase assays, microRNA-23a-3p was found to directly target eight genes, namely NOL4, SOX6, GOLGA6C, PCDHA9, G2E3, ZNF695, CEP41, and RGPD1, while microRNA-23b-3p directly targeted three genes, namely SOX6, GOLGA6C, and ZNF695. The intentional alteration of the microRNA-23a/b binding site within the 30 untranslated regions (30UTRs) of the eight genes resulted in the loss of responsiveness to microRNA-23a/b-3p. This confirmed that NOL4, SOX6, GOLGA6C, PCDHA9, and CEP41 are direct targets for microRNA23a-3p, while NOL4, SOX6, and PCDHA9 are direct targets for microRNA-23b-3p. The sperm samples of oligoasthenozoospermic men had lower expression levels of target genes than age-matched normozoospermic men. Correlation analysis indicated a positive correlation between basic semen parameters and lower expression levels of target genes. The study suggests that microRNA-23a/b-3p plays a significant role in spermatogenesis by controlling the expression of target genes linked to males with impaired fertility and has an impact on basic semen parameters

High power diode-bar-pumped Nd:YAG laser at 946nm

Diode-pumped Nd:YAG lasers operating at ~946nm are potentially attractive sources since they can be frequency-doubled to the blue. However, efficient lasing on the 946nm transition is considerably more difficult to achieve than on the more familiar 1.064µm transition. This is partly due to its quasi-three-level nature which results in a significant reabsorption loss which (at room temperature) is ~0.8%/mm for a 1% Nd doped YAG rod. The main problem however, with the 946nm line, is its small stimulated emission cross-section which is ~9 times smaller than for the 1.064µm line. As a result, 946nm Nd:YAG lasers have a threshold which is at least a factor of 9 times higher than for a comparable 1.064µm laser