Effect of ocean acidification on early life stages of Atlantic herring (Clupea harengus L.)

Due to atmospheric accumulation of anthropogenic CO2 the partial pressure of carbon dioxide (pCO2) in surface seawater increases and the pH decreases. This process known as ocean acidification might have severe effects on marine organisms and ecosystems. The present study addresses the effect of ocean acidification on early developmental stages, the most sensitive stages in life history, of the Atlantic herring (Clupea harengus L.). Eggs of the Atlantic herring were fertilized and incubated in artificially acidified seawater (pCO2 1260, 1859, 2626, 2903, 4635 μatm) and a control treatment (pCO2 480 μatm) until the main hatch of herring larvae occurred. The development of the embryos was monitored daily and newly hatched larvae were sampled to analyze their morphometrics, and their condition by measuring the RNA/DNA ratios. Elevated pCO2 neither affected the embryogenesis nor the hatch rate. Furthermore the results showed no linear relationship between pCO2 and total length, dry weight, yolk sac area and otolith area of the newly hatched larvae. For pCO2 and RNA/DNA ratio, however, a significant negative linear relationship was found. The RNA concentration at hatching was reduced at higher pCO2 levels, which could lead to a decreased protein biosynthesis. The results indicate that an increased pCO2 can affect the metabolism of herring embryos negatively. Accordingly, further somatic growth of the larvae could be reduced. This can have consequences for the larval fish, since smaller and slow growing individuals have a lower survival potential due to lower feeding success and increased predation mortality. The regulatory mechanisms necessary to compensate for effects of hypercapnia could therefore lead to lower larval survival. Since the recruitment of fish seems to be determined during the early life stages, future research on the factors influencing these stages are of great importance in fisheries science

Immunostimulation in Early Life Stages of European Sea Bass (Dicentrarchus labrax)

The reliable production of high quality juvenile fish is still hampered in marine aquaculture due to the enormous mortality in the larval stages, which is often caused by the outbreak of infectious diseases. Early life stages are extremely susceptible towards pathogens because they lack a mature immune system. Conventional disease prevention relies on the prophylactic use of antibiotics, selecting for antibiotic-resistant bacteria making treatments less and less efficient. Accordingly, the development of alternative health management strategies is one of the key factors for the progress towards a more sustainable aquaculture industry. A possibility to increase the disease resistance in early developmental stages is the stimulation of the immune system by steering the gastrointestinal microbiota. Even though it is recognized that a healthy gastrointestinal microbiota is a prerequisite for the host´s well-being, the mechanisms underlying the interdependency between gastrointestinal microbiota and immunity are not very well understood in fish. In my thesis, I explored different possibilities to stimulate the immune system in early life stages of European sea bass (Dicentrarchus labrax), a key species in European aquaculture. I investigated immunological processes on a cellular and molecular level as well as the larval microbiota, life history traits and disease resistance

Niederschlags- und Temperaturextreme: Wie gut werden sie vom statistischen Klimamodell WEREX V wiedergegeben?

KlimawandelKlimatische Extreme sind meist von besonderem Interesse, wenn mögliche Folgen eines sich ändernden Klimas auf verschiedene sozio-ökonomische Bereiche der Gesellschaft betrachtet werden. Derzeit weisen Globale und Regionale Klimamodelle (GCM/ RCM) jedoch meist noch große Unzulänglichkeiten bei der Abbildung von Extremen auf. Statistische Regionalisierungsmethoden stimmen methodenbedingt meist besser mit klimatischen Beobachtungen überein als RCMs, zumindest bei klimatischen Mittelwerten. Die Güte der Abbildung von Klimaextremen des Modells WERX V soll Inhalt dieses Beitrages sein. WEREX V ist der aktuellste regionale Klimaprojektionsdatensatz für den Freistaat Sachsen. Ein Ensemble (12 Mitglieder) aus drei GCM (ECHAM 5/MPI-OM, HadCM3C, HadGEM2), genesteten RCM (CLM, REMO, RACMO) und Szenarien (A1B, E1) wurden als Antrieb für die statistische Regionalisierungsmethode WEREX V verwendet, die eine auf Sachsen fokussierte Instanz der WETTREG-Methode darstellt. Die insgesamt 120 Klimaprojektionen werden hauptsächlich mittels ihrer Perzentile für die Periode 1961-2000 analysiert. Für die Temperatur sind dies das 10. und 90. und für den Niederschlag das 80., 90., 95. und 99. Perzentil. Mit Beobachtungsdaten verglichen wird zum einen die Höhe der Perzentile. Für Sachsen wurde eine zeitlich variable Auftretenshäufigkeit von Extremniederschlägen in den letzten 40 Jahren festgestellt. Deshalb wird zum anderen überprüft, ob WEREX V diese Variabilität abbildet. Des Weiteren werden Extremperioden wie Hitzewellen und Dürreperioden untersucht. Für letztere wird der Standardisierte Niederschlags-Evaporations-Index SPEI verwendet, der somit auch Aussagen zur elementübergreifenden Konsistenz der simulierten Datensätze ermöglicht. Ziel ist es, Stärken und Schwächen der Projektionsdatensätze zu identifizieren, um gezielte Anwendungen für die Impaktmodellierung zu ermöglichen. Perspektivisch sollen Lösungsmöglichkeiten aufgezeigt werden, die Güte der Modelle für die Abbildung von Klimaextremen zu verbessern

Immune stimulation in European sea bass (Dicentrarchus labrax) larvae by administration of Poly-ß-hydroxybutyrate (PHB)

Global aquaculture production is growing rapidly, however, the industry is facing great challenges such as high mortality rates during early life stages. The lack of a fully mature immune system makes larvae highly sensitive to infectious diseases. One of the most common pathogenic bacteria in larviculture is Vibrio anguillarum causing worldwide severe economic losses. Due to the development of antibiotic resistances, the establishment of alternative methods to prevent and control diseases, ensure efficient growth and reach maximal survival rates is mandatory to optimize aquaculture productivity. A promising solution might be the early activation of the immature immune system of fish larvae by administration of immunostimulants as nutritional supplements. In our study we assessed the potential immunomodulatory effect of poly-ß-hydroxybutyrate (PHB) in European sea bass (Dicentrarchus labrax) larvae. PHB is a bacterial energy storage compound which may have a potential application as an immunostimulant in fish culture. In our experiment we used rotifers as live carriers to feed PHB-accumulating bacteria (Alcaligenes eutrophus) to first-feeding European sea bass larvae over a period of 14 days. To estimate the immediate impact of PHB, larval mortality rates were monitored daily during the course of the experiment. In order to assess the disease resistance of the larvae, survival rates after bath challenge with Vibrio anguillarum after 3 and 14 days of PHB treatment and 7 days post PHB treatment were monitored. Furthermore, we determined gene expression profiles for immune genes as well as metabolism- and stress-related genes. Results will be discussed in respect to the use of PHB in fish hatcheries and its effect on the immune system of first feeding sea bass

Does poly-ß-hydroxybutyrate stimulate the immune system of European sea bass larvae?

Introduction Various probiotics and immunostimulants have been shown to enhance the immune response and alter the disease resistance of aquaculture organisms. The bacterial energy storage compound poly-ß-hydroxybutyrate (PHB) for example improves resistance against pathogenic infections in shrimp (Laranja et al., 2014) and exhibits a controlling effect on the gut microbiota of juvenile sea bass which may result in the stimulation of immune functions (De Schryver et al., 2011). These properties might be of special importance for culturing early life stages since their immune system is not yet fully developed. Therefore, we assessed the potential immunostimulating effect of PHB in European sea bass (Dicentrarchus labrax) larvae in our study. Materials and methods We used rotifers as live carriers to feed PHB-accumulating bacteria (Alcaligenes eutrophus) to first-feeding larvae over a period of 14 days. Bacteria with a low (2.5%) and a high (75%) PHB content were used, respectively. Apart from the dose effect, we wanted to determine to which extend the point in time of the PHB administration matters. Therefore, PHB was added (in some experimental groups) directly to the water from the moment of mouth opening onwards. This led to the following experimental groups: 1) early and 2) later stimulation with a low PHB level, 3) early and 4) later stimulation with a high PHB level and 5) a control without any PHB. To estimate the immediate impact of PHB, larval mortality rates were monitored daily over the course of the experiment. Furthermore, larvae were sampled the first time after being fed for 3 days with PHB encapsulated in rotifers (and 5 days of PHB water treatment) and the second time after 14 days PHB via rotifers (and 16 days of PHB water treatment), respectively. Results and discussion Larval mortality rates were found to be the highest in the control group. During both sampling points larvae were slightly smaller and weighed less in the control group. The analysis of the gene expression profiles revealed that only certain immune genes such as cytokines (Interleukin-1ß, Interleukin 8 and TNFα) were affected by the PHB treatment. The data indicate that the application of PHB can provide a beneficial effect to sea bass larviculture in terms of higher survival rates. But further studies are required to verify the impact on the developing immune system of the larvae

Charakterisieung des Pseudomonas aeruginosa Methioninstoffwechsels unter Bedingungen ähnlich denen einer chronischen zystischen Fibrose Lungeninfektion

The first part of this study investigated the influence of the growth conditions in the cystic fibrosis (CF) airways on the infecting Pseudomonas aeruginosa strains. A global transcriptional analysis of P. aeruginosa gene expression under simulated respiratory tract conditions in vitro in artificial sputum medium (ASM) and under ex vivo CF lung infection conditions was performed. Iron limitation was identified as the crucial factor in the CF airways in vivo. Therefore, ASM-Chelex with increased iron limitation was developed. In conclusion ASM-Chelex mimics in vivo lung infection conditions more precisely. In the second part methionine auxotrophy as adaptation strategy of P. aeruginosa towards the chronic CF lung infection was investigated. In total 30 P. aeruginosa strains isolated from 15 different CF patients were classified by single-nucleotide polymorphisms analysis (SNP). As genetic cause of methionine auxotrophy the gene metF of the cofactor biosynthesis was identified in the majority of investigated clinical isolates. The gene metF encodes for a methylenetetrahydrofolate reductase. It was verified that the methionine auxotrophy is selected independently of the mutator phenotype. Notably, the production of the major virulence factor pyocyanin was reduced in all methionine auxotrophic clinical isolates, in PAO1 ∆metF and several methionine metabolism deletion strains. The possible reduced intracellular SAM level was discussed as cause. A transcriptome analysis of PAO1 ∆metF showed upregulation of iron regulated genes. The influence of methionine auxotrophy on iron homeostasis and the possible advantage in iron acquisition of PAO1 ∆metF was discussed. In the third part the antimicrobial activity of ribavirin against P. aeruginosa PAO1 was verified. S-Adenosylhomocysteine hydrolase SahH seems not to be the main target of ribavirin in P. aeruginosa. The inhibition of the enzyme SahH by ribavirin was very low. However, it was shown that the enzyme SahH is an essential part of bacterial metabolism and therefore a powerful drug target candidate. In summary this thesis contributes to the understanding of the underlying adaptation strategies of P. aeruginosa during the CF infection and indicates possible therapeutic strategies.Im ersten Teil dieser Arbeit wurde der Einfluss der Wachstumsbedingungen in den zystische Fibrose (CF) Luftwegen auf die infizierenden Pseudomonas aeruginosa Stämme untersucht. Eine globale Transkriptionsanalyse der P. aeruginosa Genexpression wurde sowohl unter simulierten Respirationstraktbedingungen in artifiziellem Sputum-Medium (ASM) als auch unter ex vivo CF Lungeninfektionsbedingungen durchgeführt. Dabei wurde Eisenmangel als der entscheidende Faktor in den CF Luftwegen in vivo identifiziert. Daraufhin wurde ASM-Chelex mit erhöhter Eisenlimitierung entwickelt. Zusammenfassend imitiert ASM-Chelex die in vivo Lungeninfektionsbedingungen präziser. Im zweiten Teil wurde die Methioninauxotrophie als Anpassungsstrategie von P. aeruginosa an die chronische CF Lungeninfektion untersucht. Insgesamt wurden 30 P. aeruginosa Stämme von 15 verschiedenen CF Patienten isoliert und durch Einzelnukleotid-Polymorphismen (SNP) klassifiziert. Als genetische Ursache für die Methioninauxotrophie wurde das Gen metF der Kofaktorbiosynthese für die Mehrheit der untersuchten klinischen Isolate identifiziert. Das Gen metF kodiert für eine Methylentetrahydrofolat-Reduktase. Es wurde bewiesen, dass die Methioninauxotrophie unabhängig vom Mutatorphänotyp selektioniert wird. Die Produktion des bedeutenden Virulenzfaktors Pyocyanin war in allen methioninauxotrophen klinischen Isolaten, in PAO1 ∆metF und in verschiedenen Methioninstoffwechseldeletionsmutaten reduziert. Als Grund wurde der mögliche verringerte SAM-Spiegel diskutiert. Die Transkriptomanalyse von PAO1 ∆metF zeigte, dass eisenregulierte Gene stärker exprimiert wurden. Der Einfluss der Methioninauxotrophie auf die Eisenhomöostase und mögliche Eisenbeschaffungsvorteile für PAO1 ∆metF wurde diskutiert. Im dritten Teil wurde die antimikrobielle Aktivität von Ribavirin gegen P. aeruginosa PAO1 nachgewiesen. Die S-Adenosylhomocystein-Hydrolase SahH scheint nicht der Hauptangriffspunkt von Ribavirin in P. aeruginosa zu sein. Die Inhibition des Enzyms SahH durch Ribavirin war sehr gering. Es wurde jedoch gezeigt, dass das Enzym SahH ein essentieller Bestandteils des bakteriellen Stoffwechsels ist und sich daher besonders gut als Ziel für Antibiotika eignet. Diese Arbeit trägt zum Verständnis der zugrunde liegenden Anpassungsstrategien von P. aeruginosa während der CF Infektion bei und zeigt mögliche therapeutische Strategien auf

The sponge holobiont in a changing ocean: from microbes to ecosystems

The recognition that all macroorganisms live in symbiotic association with microbial communities has opened up a new field in biology. Animals, plants, and algae are now considered holobionts, complex ecosystems consisting of the host, the microbiota, and the interactions among them. Accordingly, ecological concepts can be applied to understand the host-derived and microbial processes that govern the dynamics of the interactive networks within the holobiont. In marine systems, holobionts are further integrated into larger and more complex communities and ecosystems, a concept referred to as “nested ecosystems.” In this review, we discuss the concept of holobionts as dynamic ecosystems that interact at multiple scales and respond to environmental change. We focus on the symbiosis of sponges with their microbial communities—a symbiosis that has resulted in one of the most diverse and complex holobionts in the marine environment. In recent years, the field of sponge microbiology has remarkably advanced in terms of curated databases, standardized protocols, and information on the functions of the microbiota. Like a Russian doll, these microbial processes are translated into sponge holobiont functions that impact the surrounding ecosystem. For example, the sponge-associated microbial metabolisms, fueled by the high filtering capacity of the sponge host, substantially affect the biogeochemical cycling of key nutrients like carbon, nitrogen, and phosphorous. Since sponge holobionts are increasingly threatened by anthropogenic stressors that jeopardize the stability of the holobiont ecosystem, we discuss the link between environmental perturbations, dysbiosis, and sponge diseases. Experimental studies suggest that the microbial community composition is tightly linked to holobiont health, but whether dysbiosis is a cause or a consequence of holobiont collapse remains unresolved. Moreover, the potential role of the microbiome in mediating the capacity for holobionts to acclimate and adapt to environmental change is unknown. Future studies should aim to identify the mechanisms underlying holobiont dynamics at multiple scales, from the microbiome to the ecosystem, and develop management strategies to preserve the key functions provided by the sponge holobiont in our present and future oceans

2010) “Sustainable conflict transformation: an analytical model for assessing the contribution of development activities to peacebuilding

Abstract Despite the widely recognized importance of the link between security and development, there has not been any systematic analysis of the contributions of development actors to post-conflict reconstruction and sustained peacebuilding. The model of sustainable conflict transformation (SCT) developed in this article provides a framework for assessing the contributions of development actors to peacebuilding efforts. More specifically, structuring the SCT model around the topical sectors provided by the UN's Peacebuilding Capacity Inventory generates an assessment tool that enables us to account specifically for measures aimed at aiding the transformation of cognitive conflict motivators such as conflict attitudes and identities