Bifidobacterium - Human Host Interaction: Role of Human Plasminogen

Bifidobacterium is an important genus of the human gastrointestinal microbiota, affecting several host physiological features. Despite the numerous Bifidobacterium related health-promoting activities, there is still a dearth of information about the molecular mechanisms at the basis of the interaction between this microorganism and the host. Bacterial surface associated proteins may play an important role in this interaction because of their ability to intervene with host molecules, as recently reported for the host protein plasminogen. Plasminogen is the zymogen of the trypsin-like serine protease plasmin, an enzyme with a broad substrate specificity. Aim of this thesis is to deepen the knowledge about the interaction between Bifidobacterium and the human plasminogen system and its role in the Bifidobacterium-host interaction process. As a bifidobacterial model, B. animalis subsp. lactis BI07 has been used because of its large usage in dairy and pharmaceutical preparations. We started from the molecular characterization of the interaction between plasminogen and one bifidobacterial plasminogen receptor, DnaK, a cell wall protein showing high affinity for plasminogen, and went on with the study of the impact of intestinal environmental factors, such as bile salts and inflammation, on the plasminogen-mediated Bifidobacterium-host interaction. According to our in vitro findings, by enhancing the activation of the bifidobacterial bound plasminogen to plasmin, the host inflammatory response results in the decrease of the bifidobacterial adhesion to the host enterocytes, favouring bacterial migration to the luminal compartment. Conversely, in the absence of inflammation, plasminogen acts as a molecular bridge between host enterocytes and bifidobacteria, enhancing Bifidobacterium adhesion. Furthermore, adaptation to physiological concentrations of bile salts enhances the capability of this microorganism to interact with the host plasminogen system. The host plasminogen system thus represents an important and flexible tool used by bifidobacteria in the cross-talk with the host.

Host immune response in immunodeficient mice against infection with Cryptosporidium parvum

Immunantwort von immundefizienten Mäusen gegenüber Infektionen mit Cryptosporidium parvum. Cryptosporidium parvum ist ein intrazellulärer, protozoischer Krankheitserreger, der im immunkompromittierten Wirt zu lebensbedrohender Enteritis führen kann. CD4+ T-Zellen und Interferon (IFN)-γ spielen wesentliche Rollen bei der Wirtsimmunantwort gegen die Infektion. Dennoch sind die Effektormechanismen, die zur Resistenz führen nur wenig verstanden. In dieser Studie wurde die Immunantwort von IFN-γ- und Interleukin (IL)-12-Defektmäusen parallel zu Wildtypmäusen analysiert. Die Ergebnisse identifizierten IFN-γ als Schlüsselzytokin bei der natürlichen und erworbenen Immunität während der Erst- und Folgeinfektion mit C. parvum. Tumornekrosefaktor (TNF)-α ist möglicherweise ein Induktor der frühen IFN-γ-Antwort in IL-12 Knockout-Mäusen. Weiterhin tragen offenbar sowohl Th1- als auch Th2-Zytokine zur Überwindung der Primärinfektion bei, die ersten mehr als die letztgenannten. Zytokingene waren am Ort der Infektion (Ileum) dramatisch verändert, nicht aber in den lokalen Lymphknoten und der Milz. Nach Folgeinfektion ergab sich in Abwesenheit von IFN-γ eine signifikante Erhöhung der Th2-Zytokine IL-5 and IL-13. Die Ergebnisse zeigten weiterhin, dass das Th1-Zytokin IL-18 zur Resistenz gegenüber C. parvum beiträgt, möglicherweise durch verschiedene Immunfunktionen, wie der Regulation von Serum-IFN-γ während der Infektion und/oder der Erhaltung der Homeostase der Th1/Th2-Zytokine durch Regulation der Th2-Zytokine. Weiterhin zeigten diese Untersuchungen den Transfer von Resistenz gegenüber C. parvum von infizierten auf naïve Mäuse mittels stimulierter intraepithelialer Lymphozyten und CD4+ T-Zellen. Diese Ergebnisse weisen auf die Gegenwart von C. parvum-spezifischen CD4+ T-Zellen in anderen lymphatischen Geweben neben der Darmmukosa hin. Eine Stimulation der Spendertiere durch Infektion war notwendig für eine übertragbare schützende Immunität. Dennoch konnte die übertragene Immunität nicht die Infektion der Empfängertiere vollständig verhindern; eine Verdopplung der Spenderzellen führte zu keinem besseren Ergebnis. Weiterhin ergab der Transfer von CD4+ und CD8+ T-Zellen (Pan-T-Zellen) keinen erhöhten Schutz der naiven Empfängertiere als der alleinige Transfer von CD4+ T-Zellen. Dies weist auf die fehlende Bedeutung der CD8+ T-Zellen beim Schutz vor C. parvum-Infektion hin.

New associations between native parasitoids and exotic insects introduced in Italy and in Europe

The introduction of exotic species is one of the most important threats to biodiversity.This phenomenon may cause economic and environmental damage. To prevent these invasions there are institutions like EPPO. Nevertheless, the introduction of exotic pests is an increasing issue, difficult to control. Classic biological control, based on importation of natural enemies from the country of origin, has been successfully used for over 120 years, but it has also raised some criticism. My research work has focused on the study of the new associations occurring between indigenous parasitoids and three exotic pests introduced in Italy and Europe. The three target insects considered were: Cacyreus marshalli Butler (Lepidoptera: Lycaenidae), a pest of Geranium plants; Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), a plague of Castanea sp. and Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). This ladybug has been introduced as a biological control agent, but since some years it considered as an invasive species. For C. marshalli I performed laboratory tests on acceptance and suitability of immature stages of this butterfly by Exorista larvarum (Diptera: Tachinidae) and Brachymeria tibialis (Hymenoptera: Chalcidicae). The experiments showed that these two parasitoids could be used to contain this pest. For D. kuriphilus I performed field samplings in an infested chestnut area, the samples were maintained in rearing chamber until gall wasp or parasitoids emergence. In the 3-year research many parasitoids of gall wasps were found; one of these, Torymus flavipes (Walker), was found in large number. For H. axyridis the research work included a first phase of field sampling, during which I searched indigenous parasitoids which had adapted to this new host; the only species found was Dinocampus coccinellae (Schrank) (Hymenoptera: Braconidae). Laboratory tests were performed on the wasp rearing, biology and capacity to contain H. axyridis.

Cell Host-Microbe Interactions: Turning Pathogen Mechanisms Into Cell's Advantages

Host-Pathogen Interaction is a very vast field of biological sciences, indeed every year many un- known pathogens are uncovered leading to an exponential growth of this field. The present work lyes between its boundaries, touching different aspects of host-pathogen interaction: We have evaluate the permissiveness of Mesenchimal Stem cell (FM-MSC from now on) to all known human affecting herpesvirus. Our study demonstrate that FM-MSC are full permissive to HSV1, HSV2, HCMV and VZV. On the other hand HHV6, HHV7, EBV and HHV8 are susceptible, but failed to activate a lytic infection program. FM-MSC are pluripotent stem cell and have been studied intensely in last decade. FM-MSC are employed in some clinical applications. For this reason it is important to known the degree of susceptibility to transmittable pathogens. Our atten- tion has then moved to bacterial pathogens: we have performed a proteome-wide in silico analy- sis of Chlamydiaceae family, searching for putative Nuclear localization Signal (NLS). Chlamy- diaceae are a family of obligate intracellular parasites. It’s reasonably to think that its members could delivered to nucleus effector proteins via NLS sequences: if that were the case the identifi- cation of NLS carrying proteins could open the way to therapeutic approaches. Our results strengthen this hypothesis: we have identified 72 protein bearing NLS, and verified their func- tionality with in vivo assays. Finally we have conceived a molecular scissor, creating a fusion protein between HIV-1 IN protein and FokI catalytic domain (a deoxyexonuclease domain). Our aim is to obtain chimeric enzyme (trojIN) which selectively identify IN naturally occurring target (HIV LTR sites) and cleaves subsequently LTR carrying DNA (for example integrated HIV1 DNA). Our preliminary results are promising since we have identified trojIN mutated version capable to selectively recognize LTR carrying DNA in an in vitro experiments.

Distribuzione, prevalenza e host range della Skeleton Eroding Band nell'atollo di Faafu, Repubblica delle Maldive

Lo studio delle malattie che colpiscono i coralli rappresenta un campo di ricerca nuovo e poche sono le ricerche concentrate nell’Oceano Indo-Pacifico, in particolare nella Repubblica delle Maldive. Lo scopo di questa ricerca è stato approfondire le conoscenze riguardo distribuzione, prevalenza e host range della Skeleton Eroding Band (SEB) nell’atollo di Faafu. Durante il lavoro, svolto in campo tra il novembre e il dicembre 2013, sono state indagate le isole di: Magoodhoo, Filitheyo e Adangau al fine di rilevare differenze nei livelli di prevalenza della SEB in relazione ai diversi gradi di utilizzo da parte dell’uomo delle 3 isole. Il piano di campionamento ha previsto la scelta casuale, in ciascuna delle isole, di 4 siti in cui sono stati realizzati 3 belt transect e 3 point intercept transect a 2 profondità predefinite. La SEB è stata ritrovata con una prevalenza media totale di 0,27%. Dai risultati dell’analisi statistica le differenze fra le isole non sono apparse significative, facendo ipotizzare che i livelli di prevalenza differiscano a causa di oscillazioni casuali di carattere naturale e che quindi non siano dovute a dinamiche legate al diverso sfruttamento da parte dell’uomo. I generi Acropora e Pocillopora sono risultati quelli maggiormente colpiti con valori di prevalenza totale di 0,46% e 1,33%. Infine è stata rilevata una correlazione positiva tra il numero di colonie di madrepore affette dalla SEB e il numero di colonie in cui la malattia è associata alla presenza di lesioni provocate da danni meccanici. I dati di prevalenza ottenuti e le previsioni di cambiamenti climatici in grado di aumentare distribuzione, host range, abbondanza della patologia, pongono l’accento sulla necessità di chiarire il ruolo delle malattie dei coralli nel deterioramento, resilienza e recupero dei coral reefs, al fine di attuare politiche di gestione adatte alla protezione di questi fragili ecosistemi.

Drosophila melanogaster as a model to study host-parasitoid interactions: the case of the polydnaviral protein TnBVANK1

Parasitic wasps attack a number of insect species on which they feed, either externally or internally. This requires very effective strategies for suppressing the immune response and a finely tuned interference with the host physiology that is co-opted for the developing parasitoid progeny. The wealth of physiological host alterations is mediated by virulence factors encoded by the wasp or, in some cases, by polydnaviruses (PDVs), unique viral symbionts injected into the host at oviposition along with the egg, venom and ovarian secretions. PDVs are among the most powerful immunosuppressors in nature, targeting insect defense barriers at different levels. During my PhD research program I have used Drosophila melanogaster as a model to expand the functional analysis of virulence factors encoded by PDV focusing on the molecular processes underlying the disruption of the host endocrine system. I focused my research on a member of the ankyrin (ank) gene family, an immunosuppressant found in bracovirus, which associates with the parasitic wasp Toxoneuron nigriceps. I found that ankyrin disrupts ecdysone biosynthesis by impairing the vesicular traffic of ecdysteroid precursors in the cells of the prothoracic gland and results in developmental arrest.

Mechanismen zur Suppression der experimentellen akuten Graft-versus-Host-Disease

Die Transplantation von allogenen hämatopoetischen Stammzellen stellt für viele Patienten mit hämatologischen Erkrankungen, wie beispielsweise akuter Leukämie, oftmals die einzige kurative Therapieoption dar. Die Erkennung von Empfängerantigenen durch immunkompetente Zellen des Spenders bietet dabei die Basis für erwünschte Graft-versus-Tumor-Effekte, verursacht jedoch häufig außerdem die unerwünschte Graft-versus-Host Disease (GvHD), eine mitunter schwerwiegende Komplikation. In der vorliegenden Arbeit wurden potentielle Mechanismen zur Hemmung alloreaktiver CD4+ und CD8+ T-Zellen (TZ) und folglich zur Hemmung der akuten GvHD in einem experimentellen GvHD-Modell untersucht, welches auf dem Transfer von allogenen Zellen zwischen MHC-inkompatiblen Mausstämmen basiert. Die vorliegende Arbeit weist zum Einen darauf hin, dass das Fehlen MyD88- und TRIF-vermittelter Toll-like-Rezeptor-Signale zumindest im Rahmen des hier verwendeten Transplantationsmodells nicht zwingend zu einer Hemmung der akuten GvHD führt. Zum Anderen konnte belegt werden, dass CD4+ CD25+ regulatorische T-Zellen (Tregs) kompetente Suppressoren der durch alloreaktive CD4+ und CD8+ TZ ausgelösten akuten GvHD darstellen. In weiterführenden Experimenten ist gezeigt worden, dass die Tregs sich verschiedener Mechanismen bedienen, um ihre Zielzellen zu inhibieren. Das suppressive Zytokin Interleukin-10 kann als löslicher Mediator zumindest in vitro offenbar eine Rolle bei der Treg-vermittelten Suppression alloreaktiver TZ spielen. Da jedoch auch Tregs aus Interleukin-10-defizienten Spendern die GvHD-Entstehung in den Empfängern abschwächen konnten, müssen noch weitere Mechanismen involviert sein. Es konnte in einer gemischten Leukozyten Reaktion in vitro eine zellkontaktabhängige Kommunikation mittels gap junctions hauptsächlich zwischen den Tregs und den allogenen Dendritischen Zellen (DCs) nachgewiesen werden, welche prinzipiell den Transfer von cAMP möglich macht. Die Kommunikation zwischen Tregs und DCs resultierte in einem supprimierten Phänotyp der DCs, gekennzeichnet durch eine verminderte Expression kostimulatorischer Moleküle auf ihrer Oberfläche. Solche supprimierten DCs können als Folge die alloreaktiven Spender-TZ vermutlich nicht aktivieren. Das cAMP-erhöhende Rolipram konnte in einer gemischten Leukozyten Reaktion in vitro die Proliferation alloreaktiver CD4+ und CD8+ TZ hemmen. Daneben konnte die Treg-vermittelte Suppression alloreaktiver TZ und der GvHD in vivo durch die zusätzliche Verabreichung von Rolipram noch gesteigert werden. Im letzten Kapitel dieser Arbeit wurde beschrieben, dass die alleinige Aktivierung alloreaktiver CD8+ TZ ausreichend ist, um eine akute GvHD auszulösen. In diesem Zusammenhang konnte nachgewiesen werden, dass CD4+ CD25+ Tregs die akute GvHD auch in einer scheinbar MHC-II-unabhängigen Weise hemmen können. Zusammenfassend belegt die vorliegende Arbeit, dass Tregs in einem MHC-inkompatiblen Transplantationsmodell alloreaktive CD4+ und CD8+ TZ und folglich die Entstehung einer GvHD effizient hemmen können. Bei der Hemmung der GvHD kommen wahrscheinlich verschiedene Mechanismen zum Tragen. Zumindest in vivo scheint von Tregs produziertes Interleukin-10 eine untergeordnete Rolle bei der Suppression alloreaktiver TZ und der GvHD zu spielen, hierbei steht vermutlich vielmehr der cAMP-abhängige Suppressionsmechanismus im Vordergrund.

Staphylococcus aureus bones and joints infections: in vivo studies and host immune response

Abstract The aim of this work was the development of a murine model of septic arthrosynovitis and osteomyelitis caused by Staphylococcus aureus, which could mimic the natural disease occurring in humans and which could be suitable for testing preventive and therapeutic interventions. This model could be particularly useful since S. aureus-mediated joints and bones infections are relevant in humans, both in terms of frequency and severity. Our attention focused in tracking bacterial infiltration in joints and bones over time using different microbiological and hystopathological tools, which allowed us to have a complete overview of the situation and to evaluate the immunological actions undertaken by the host to contain or eradicate the bacterial infection. Antibodies and cytokines profiles, as well as recruitment of host immune cells at joints of immunized and infected mice were therefore monitored for a time period that allowed us to study both the acute and the chronic phases of the disease in situ. Finally the Novartis vaccine formulation proposed against S. aureus infections was tested for its capacity to protect immunized mice from joints infections, and the preventive immunization was compared to a standard antibiotic prophylaxis. The availability of powerful tools to study specific bacterial-mediated diseases is nowadays an important requirement for the scientific community to shed light on the complex interactions between host and pathogens and to test treatments for preventing or contrasting infections. We believe that our work significantly contributes to the overall knowledge in the field of S. aureus-dependent pathologies, opening the possibility for further investigations in several fields of study.

X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies

In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN space density is found to decrease by a factor of 10 from z=3 to z=5. I also found that about 50% of AGN are obscured by large column densities (logNH > 23). By comparing these data with those in the Local Universe, I found a positive evolution of the obscured AGN fraction with redshift, especially for luminous (logLx > 44) AGN. I also studied the gas content of z < 1 AGN-hosting galaxies and compared it with that of inactive galaxies. For the first time, I applied to AGN a method to derive the gas mass previously used for inactive galaxies only. AGN are found to live preferentially in gas-rich galaxies. This result on the one hand can help us in understanding the AGN triggering mechanisms, on the other hand explains why AGN are preferentially hosted by star-forming galaxies.

Host mi? Asterix und Obelix auf bairisch

La tesi analizza il dialetto bavarese sulla base di un confronto fra il fumetto di Asterix e Obelix in bavarese e tedesco standard. Die vorliegende Bachelorarbeit ist eine Analyse des bairischen Dialekts. Der Ausgangspunkt ist der Comic von Asterix und Obelix auf Bairisch.

Aggression and its function as a hub mediating host defense against the slavemaking ant Protomognathus americanus

In meiner Dissertation beschäftigte ich mich mit unterschiedlichen Verteidungsstrategien, derenrnEffektivität und Evolution, der Ameisenart Temnothorax longispinosus (“Sklaven”), gegenüberrneinem sozialen Parasiten - der nahverwandten, sklavenhaltenden Art Protomognathusrnamericanus (“Sklavenhalter”). Wir entdeckten eine neue Kategorie der Verteidigungsstrategie,rnwelche es dem Wirten ermöglicht, flexibel auf die nicht vorhersagbaren Angriffe des Parasitenrnzu reagieren. Darüber hinaus erforschten wir, wie die Wirte ihre kollektive Verteidigung an einernVielzahl unterschiedlicher Angreifer anpassen können. Wir konnten feststellen, dass Wirte in derrnLage sind ihre kollektive Verteidigung dem Grad der Bedrohung anzupassen. Dies weist daraufrnhin, dass Selektion die Verteidigung gegen unterschiedliche Typen von Angreifern voneinanderrnunabhängig beeinflussen könnte. In einer dritten Studie belegten wir experimentell, dass diernParasiten die Evolution der Kolonieaggressivität der Wirtsart direkt beeinflussen. Die letztenrnbeiden Publikationen beschäftigten sich mit Sklavenrebellion, einer rätselhaftenrnVerteidigungsstrategie, da noch unklar ist, wie eine Eigenschaft von nicht reproduzierendenrnIndividuen vererbt werden kann. In einer Metaanalyse konnten wir die weite Verbreitung undrnhohe Variabilität dieser Eigenschaft dokumentieren, und fanden Hinweise, dassrnVerwandtenselektion eine mögliche Erklärung für die Evolution dieses Merkmals darstellenrnkönnte.

Exploring host-pathogen interactions through protein microarray. Large-scale protein microarray analysis revealed novel human receptors for the staphylococcal immune evasion protein FLIPr and for the neisserial adhesin NadA

Adhesion, immune evasion and invasion are key determinants during bacterial pathogenesis. Pathogenic bacteria possess a wide variety of surface exposed and secreted proteins which allow them to adhere to tissues, escape the immune system and spread throughout the human body. Therefore, extensive contacts between the human and the bacterial extracellular proteomes take place at the host-pathogen interface at the protein level. Recent researches emphasized the importance of a global and deeper understanding of the molecular mechanisms which underlie bacterial immune evasion and pathogenesis. Through the use of a large-scale, unbiased, protein microarray-based approach and of wide libraries of human and bacterial purified proteins, novel host-pathogen interactions were identified. This approach was first applied to Staphylococcus aureus, cause of a wide variety of diseases ranging from skin infections to endocarditis and sepsis. The screening led to the identification of several novel interactions between the human and the S. aureus extracellular proteomes. The interaction between the S. aureus immune evasion protein FLIPr (formyl-peptide receptor like-1 inhibitory protein) and the human complement component C1q, key players of the offense-defense fighting, was characterized using label-free techniques and functional assays. The same approach was also applied to Neisseria meningitidis, major cause of bacterial meningitis and fulminant sepsis worldwide. The screening led to the identification of several potential human receptors for the neisserial adhesin A (NadA), an important adhesion protein and key determinant of meningococcal interactions with the human host at various stages. The interaction between NadA and human LOX-1 (low-density oxidized lipoprotein receptor) was confirmed using label-free technologies and cell binding experiments in vitro. Taken together, these two examples provided concrete insights into S. aureus and N. meningitidis pathogenesis, and identified protein microarray coupled with appropriate validation methodologies as a powerful large scale tool for host-pathogen interactions studies.

Evaluation of 3D cell culture systems for host-pathogen interaction studies

Traditional cell culture models have limitations in extrapolating functional mechanisms that underlie strategies of microbial virulence. Indeed during the infection the pathogens adapt to different tissue-specific environmental factors. The development of in vitro models resembling human tissue physiology might allow the replacement of inaccurate or aberrant animal models. Three-dimensional (3D) cell culture systems are more reliable and more predictive models that can be used for the meaningful dissection of host–pathogen interactions. The lung and gut mucosae often represent the first site of exposure to pathogens and provide a physical barrier against their entry. Within this context, the tracheobronchial and small intestine tract were modelled by tissue engineering approach. The main work was focused on the development and the extensive characterization of a human organotypic airway model, based on a mechanically supported co-culture of normal primary cells. The regained morphological features, the retrieved environmental factors and the presence of specific epithelial subsets resembled the native tissue organization. In addition, the respiratory model enabled the modular insertion of interesting cell types, such as innate immune cells or multipotent stromal cells, showing a functional ability to release pertinent cytokines differentially. Furthermore this model responded imitating known events occurring during the infection by Non-typeable H. influenzae. Epithelial organoid models, mimicking the small intestine tract, were used for a different explorative analysis of tissue-toxicity. Further experiments led to detection of a cell population targeted by C. difficile Toxin A and suggested a role in the impairment of the epithelial homeostasis by the bacterial virulence machinery. The described cell-centered strategy can afford critical insights in the evaluation of the host defence and pathogenic mechanisms. The application of these two models may provide an informing step that more coherently defines relevant molecular interactions happening during the infection.

Apple latent infection caused by Neofabraea alba: host-pathogen interaction and disease management

Apple latent infection caused by Neofabraea alba: host-pathogen interaction and disease management Bull’s eye rot (BER) caused by Neofabraea alba is one of the most frequent and damaging latent infection occurring in stored pome fruits worldwide. Fruit infection occurs in the orchard, but disease symptoms appear only 3 months after harvest, during refrigerated storage. In Italy BER is particularly serious for late harvest apple cultivar as ‘Pink Lady™’. The purposes of this thesis were: i) Evaluate the influence of ‘Pink Lady™’ apple primary metabolites in N. alba quiescence ii) Evaluate the influence of pH in five different apple cultivars on BER susceptibility iii) To find out not chemical method to control N. alba infection iv) Identify some fungal volatile compounds in order to use them as N. alba infections markers. Results regarding the role of primary metabolites showed that chlorogenic, quinic and malic acid inhibit N. alba development. The study based on the evaluation of cultivar susceptibility, showed that Granny Smith was the most resistant apple cultivar among the varieties analyzed. Moreover, Granny Smith showed the lowest pH value from harvest until the end of storage, supporting the thesis that ambient pH could be involved in the interaction between N. alba and apple. In order to find out new technologies able to improve lenticel rot management, the application of a non-destructive device for the determination of chlorophyll content was applied. Results showed that fruit with higher chlorophyll content are less susceptible to BER, and molecular analyses comforted this result. Fruits with higher chlorophyll content showed up-regulation of PGIP and HCT, genes involved in plant defence. Through the application of PTR-MS and SPME GC-MS, 25 volatile organic compounds emitted by N. alba were identified. Among them, 16 molecules were identified as potential biomarkers.

Host race formation in Hyalesthes obsoletus (Signoret 1865)

Die Winden-Glasflügelzikade Hyalesthes obsoletus (Cixiidae, Glasflügelzikaden) nutzte in Deutschland ursprünglich die Ackerwinde Convolvulus arvensis als Wirtspflanze, allerdings nahm in den letzten zwei Dekaden die Abundanz auf der Großen Brennnessel Urtica dioica stark zu, zusammen mit der Inzidenz der Schwarzholzkrankheit Bois noir auf Weinreben. Bois noir wird durch ein Phytoplasma verursacht, das durch H. obsoletus von C. arvensis und U. dioica auf Weinreben übertragen wird. Es stellte sich daher die Frage, ob H. obsoletus Wirtsrassen entwickelt hat, die möglicherweise die Bois noir-Epidemiologie beeinflussen. In der vorliegenden Studie wurden folgende Fragestellungen bearbeitet: rn(1) Gibt es in Deutschland und Europa genetisch unterscheidbare Wirtsrassen von H. obsoletus auf den beiden Wirtspflanzen C. arvensis und U. dioica? Es wurden sieben Mikrosatellitenmarker entwickelt und etabliert, um H. obsoletus Populationen aus Deutschland und Europa genetisch zu analysieren. Es zeigte sich eine deutliche Differenzierung zwischen Populationen von beiden Wirtspflanzen in Deutschland, jedoch nicht in den historischen Ursprungsgebieten der deutschen Populationen, in der Schweiz, Italien oder Slovenien.rn(2) Wo sind die deutschen Wirtsrassen von H. obsoletus entstanden? Eine Einwanderung von südlichen, bereits an U. dioica angepassten Individuen stand einer lokalen Wirtsrassenevolution gegenüber. Die engere genetische Verwandtschaft der deutschen Population auf U. dioica zu denen auf C. arvensis, im Vergleich zu den übrigen Populationen auf U. dioica, impliziert einen lokalen Prozess im nördlichen Verbreitungsgebiet. Eine Immigration südlicher Tiere scheint nicht zur Diversifizierung beigetragen zu haben, führte aber möglicherweise einen U. dioica-spezifischen Phytoplasma-Stamm ein. Durch Wirtsrassenevolution entwickelten sich spezifische, vektorbasierte epidemiologische Kreisläufe der Schwarzholzkrankheit Bois noir. rn(3) Welche Präferenzen zeigen die beiden Wirtsrassen von H. obsoletus für die Wirtspflanzen C. arvensis und U. dioica und unterscheiden sich diese? Die Präferenz von H. obsoletus aus beiden deutschen Wirtsrassen in Bezug auf den Geruch der Wirtspflanzen wurde in einem Y-Olfaktometer untersucht, zusätzlich wurden beide Pflanzen direkt zur Wahl gestellt. Bei beiden Untersuchungen zeigte die Population von C. arvensis eine signifikante Präferenz für ihre native Wirtspflanze. Die Population von U. dioica wies dagegen keine Präferenz für den Geruch einer Wirtspflanze auf, bevorzugte im direkten Test jedoch signifikant ihre native Wirtspflanze. Dies weist darauf hin, dass die Anpassung an den „neuen“ Wirt noch nicht vollständig ist.rn