In der vorliegenden Dissertation wurden verschiedene Themenbereiche bearbeitet, die zur Charakterisierung der intrazellulären, bakteriellen Endosymbionten im Mitteldarm von Ameisen der Gattung Camponotus beitrugen. Es wurden phylogenetische Untersuchungen mit Hilfe der 16S rDNA-Sequenzen der Symbionten und der Sequenzen der Cytochrom-Oxidase-Untereinheit I (COI-Sequenzen) ihrer Wirte durchgeführt, die zur näheren Klärung der Fragen zu Übertragungsweg und Stellung der Camponotus-Endosymbionten verhalfen. Untersuchungen an dreizehn verschiedenen Camponotus-Arten brachten folgende Ergebnisse. Die intrazellulären Bakterien der Ameisen gehören zur g-Subklasse der Proteobakterien. Innerhalb des 16S-Stammbaumes der Symbionten kann man drei Untergruppen unterscheiden, in denen die einzelnen Arten enger miteinander verwandt sind. Bei den nächstverwandten Bakteriennachbarn der Camponotus-Endosymbionten handelt es sich um die ebenfalls symbiontisch lebenden Bakterien der Gattungen Wigglesworthia und Buchnera. Die Ameisen-Symbionten besitzen in ihren rrs-Genen intervenierende DNA-Sequenzen (IVS), die stabile Sekundärstrukturen ausbilden können. Ihre 16S-Gene sind nicht strangaufwärts von den 23S-Genen lokalisiert. Durch diese genetische Besonderheit ähneln die Camponotus-Symbionten den Buchnera-Symbionten, deren rRNA-Gene auf zwei Transkriptionseinheiten verteilt sind. Innerhalb des Stammbaumes der untersuchten Wirtsameisen existieren ebenfalls drei Untergruppen, deren einzelne Arten enger miteinander verwandt sind. Die direkte Gegenüberstellung des Symbionten-Stammbaumes mit dem der Ameisen zeigt ein weitgehend gleiches Verzweigungsmuster. Beide Dendrogramme zeigen signifikante Übereinstimmungen bezüglich ihrer taxonomischen Beziehungen und legen eine kongruente Entwicklung von Symbionten und Wirten, die nur durch einen vertikalen Übertragungsweg erzeugt werden kann, nahe. Einzige Ausnahme bildete hierbei der C. castaneus-Symbiont, bei dem ein horizontaler Transfer von Symbionten nicht gänzlich ausgeschlossen werden kann. Die im Rahmen dieser Dissertation durchgeführten phylogenetischen Untersuchungen ermöglichten die Benennung einer neuen Symbiontengattung innerhalb der gamma-Subgruppe der Proteobakterien: "Candidatus Blochmannia spp." Histologische Studien der Endosymbiose mit Hilfe von licht- und elektronenmikroskopischen Methoden sollten Fragen zur Symbiontenlokalisation innerhalb adulter Individuen beantworten und die Ergebnisse zum Übertragungsweg der intrazellulären Bakterien festigen. Die Endosymbionten sind in den Mitteldarmepithelien von Arbeiterinnen, Königinnen und Männchen in Myzetozytenzellen lokalisiert, die in das Mitteldarmepithel interkalieren. Diese spezialisierten Zellen besitzen kaum Vesikel und tragen keinen Mikrovillisaum. In den Oozyten der Ovarien von Königinnen und Arbeiterinnen wurden ebenfalls große Symbiontenmengen gefunden. Die Spermatheka der Königinnen und die Geschlechtsorgane der Männchen waren symbiontenfrei. Die Abwesenheit von Symbionten innerhalb dieser beiden Organe zeigt, dass eine Bakterieninfektion der weiblichen Tiere nicht durch die Männchen stattfindet, sondern wie schon in den phylogenetischen Untersuchungen postuliert, ein rein maternaler Übertragungsweg der Symbionten vorliegt. Die Detektion der Bakterien in Eiern und Larven der Ameisen mittels In situ-Hybridisierungen trugen zur Aufklärung des Weges der Endosymbionten während der Embryogenese bei. Während sich im abgelegten Ei ein Ring aus Symbionten bildete, kam es in den Larvenstadien 1 bis 3 zur Auswanderung der Bakterien in Meso- bzw. Ektoderm. Im größten untersuchten Larvenstadium 4, das kurz vor der Verpuppung stand, konnten die Symbionten ausschließlich in den Myzetozyten des Mitteldarmes detektiert werden. Die Behandlung der Ameisen mit Antibiotika ermöglichte es, symbiontenfreie Ameisen zu erzeugen, die über einen längeren Zeitraum weiterlebten, ohne ihre Symbionten zu regenerieren. Im Rahmen dieser Arbeit gelang es erstmals, die intrazellulären Bakterien intakt aus dem sie umgebenden Mitteldarmgewebe zu isolieren. Somit konnten gereinigte Symbionten für Kultivierungs- und Infektionsversuche verwendet werden. Diese Versuche die mit Hilfe von Bakteriennährmedien und Insektenzelllinien durchgeführt wurden, zeigten jedoch sehr deutlich, dass es nicht möglich ist, die Camponotus-Symbionten außerhalb ihrer Wirte zu kultivieren. / This thesis deals with the characterization of intracellular endosymbiotic bacteria in the midgut of carpenter ants (Camponotus spp.). Sequences of the 16S rDNA of the symbionts and the mitochondrial cytochrome oxidase subunit I (COI) were used for phylogenetic analyses, respectively. These investigations led to new insights concerning the transmission pathway and the phylogenetic classification of the Camponotusendosymbionts. The following results were obtained by extensive analysis of thirteen different Camponotus species. The intracellular bacteria of these species form a distinct lineage in the gamma-subclass of the Proteobacteria. Within the Camponotus symbionts three subclusters are apparent, in which the strains are more related to each other than to the members of the other subclusters. The taxa closest related to the antsymbionts are the symbiotic bacteria of the genus Wigglesworthia and Buchnera. The rrs genes of the Camponotusendosymbionts contain putative intervening sequences (IVS). Their 16S rDNA apparently is not located upstream of the 23S rDNA, and the 16S and 23Sgenes seem to be organized in different transcription units. This genetic characteristic was already described for the symbionts of the genus Buchnera. Similar to the endosymbionts, the phylogenetic relationship of the host ants could be arranged into three clusters with increasingly closer relationship. The direct comparison of the phylogenetic trees of the endosymbiotic bacteria and the ants revealed a nearly similar branching pattern. The exception is C. castaneus, which can not be related to any other species on the basis of the COI analysis. Nevertheless, both trees showed very significant congruence suggesting parallel evolution of symbiotic bacteria and host ant species. These phylogenetic investigations provided the justification for proposing a new taxon in the gamma-subclass of the Proteobacteria: "Candidatus Blochmannia spp". By light- and electronmicroscopical studies I investigated the mode of transmission of the endosymbionts and their location in adult individuals. These studies showed that the bacteria are localized in specialized cells, so-called mycetocytes. These cells are intercalated between the epithelial cells of the midgut. The mycetocytes lack vesicles and microvilli. Camponotusendosymbionts have not been detected in spermathecae of queens or in the testes of males, but they were found intracellularly in oocytes of queens and workers. This strongly indicates a maternal transmission of the bacteria. Using in situ hybridization with species specific probes, the endosymbiotic bacteria could be detected in eggs and larvae. With these experiments it was possible to study the spatial arrangements of the symbionts during embryogenesis. In the egg-stage the symbionts form a ball. In larval stages 1-3 a migration of bacteria into the meso- and ectoderm was observed. In larval stage 4 the symbionts were accumulated in the midgut epithelium, like in adult individuals. Symbionts could only be detected in the mycetocytes of the gut. Ants treated with antibiotics were free of symbionts, and could be maintained to a long time period (more than 12 weeks) without regenerating their bacteria. In these studies we were able to isolate the symbionts out of the midgut epithelial successfully. These isolated microorganisms were used for cultivation and infection experiments. Using different culture mediums and insect cells we showed, that it is impossible to cultivate the Camponotus symbionts outside their host organisms.

Universiẗat, Diss.--Kaiserslautern, 1999.

Symbiotic associations between animals and microbes are widespread in nature, yet the factors controlling the abundance and distributions of particular symbionts are mostly unknown. Vertically transmitted (VT) symbionts can invade host populations by providing net benefits to hosts. While most beneficial symbiotic interactions that have been characterized are nutritional, other major pathways likely exist that facilitate symbiont transmission within host populations. Natural enemies, for example, are important selective forces in shaping the life history of many invertebrates and hosts may benefit from collaborations with microbes to aid in their defense.In this dissertation I have addressed the role of VT, facultative (= secondary) symbionts (SS) of Acyrthosiphon pisum in mediating interactions with an important natural enemy, the parasitic wasp, Aphidius ervi. I found that, in a common genetic background, two A. pisum SS (R- and T-type SS) confer resistance to A. ervi, by causing mortality to developing wasp larvae. Defensive mutualisms with microbes provide a mechanism for the spread and persistence of VT symbionts.A. pisum superinfected with both R- and T-type SS were found to be more resistant to parasitism that those singly infected with either SS. Despite this added benefit to resistance, R + T-type superinfections were rare in a survey of A. pisum symbionts, likely attributable to severe fecundity costs. R-type densities increased dramatically in superinfected hosts and over-proliferation of SS may result in poor aphid performance. Thus, interactions among the symbionts themselves also likely play a critical role in determining the distributions of symbionts in nature.I also found that four T-type isolates from A. pisum, and one from another aphid species, all conferred resistance to parasitism in the same A. pisum host background. The levels of resistance varied greatly among isolates, including one that conferred nearly complete resistance. A single T-type isolate was also found to confer similar levels of resistance in five A. pisum backgrounds. These results indicate that SS-mediated resistance is a general phenomenon in A. pisum and that the SS isolate is more important in determining the level of resistance than is the aphid genotype or interaction between isolate and aphid genotype.

The whitefly Bemisia tabaci species complex has been well documented as one of the most economically important emergent plant virus vectors, through serious feeding damage to its broad range of plant hosts and transmission of plant viruses to important agricultural crops. It has been shown to have associations with endosymbionts which have significant effects on the insect fitness. The purpose of this study was to provide information for the biotype and secondary endosymbiont distribution for B. tabaci populations in the relatively unstudied Arabian peninsula. The geographical localization and variation in endosymbiont populations across the region were identified using a sequence-driven analysis of the population genetics of the secondary endosymbiont. Live field specimens were collected from 22 different locations in the region and preserved in 70% ethanol for genetic studies. Previously established procedures were used to extract and purify total insect DNA from 24-30 individual whiteflies for each location (Frohlich et al., 1999; Chiel et al., 2007). Specimens were subjected to PCR amplification using the respective 16S rDNAprimers for the Rickettsia, Hamiltonella, and Wolbachia to amplify endosymbiont DNA. PCR was run with primers for the highly conserved whitefly mitochondrial cytochrome oxidase subunit I (COI) gene for biotyping. Samples were sequenced using the Sanger method and the data analyzed to correlate the presence, prevalence and geographical distribution of endosymbionts in B. tabaci. Phylogenies 5 were constructed to track evolutionary differences amongst the endosymbionts and insects and how they have influenced the evolution of the regional populations. Samples were characterized by differences in the genomes and endosymbionts of common whitefly ‘biotypes’ that have different host plant preferences, vector capacities and insecticide resistance characteristics. It was found that the B biotype is the predominant haplotype, with no evidence of the Q biotype. All endosymbionts were detected, with Hamiltonella as the most predominant. Several instances of co-infection by two or more endosymbionts were observed. Samples from the geographically isolated and mountainous region of Fayfa demonstrated higher genetic variability compared to the other locations, leading to the possible identification of a new haplotype, as well as the first time identification of the A biotype in the region.

Bacterial endosymbionts of eukaryotes are generally studied in terms of their benefit or detriment to their hosts. The constraints that the host's life history imposes on its endosymbionts are rarely considered, although bacterial genome content and size are influenced by both the biotic and abiotic factors in the environment. The host organism is the primary habitat of the endosymbiont. Thus, desecribing the environment a host provides its endosymbiont is essential for understanding the evolution of endosymbiotic bacteria. I propose a system to classify the endosymbiotic environment by three characteristics: 1) host life cycle 2) host metabolism, and 3) endosymbiont location relative to host tissues. Insect-bacterial mutualisms have been classified in terms of endosymbiont environment. The majority of insect-bacterial mutualisms currently studied involve monophagous, hemimetabolous hosts that provide a relatively constant endosymbiotic enviroment. A relatively constant environment may explain the extremely reduced genomes of their endosymbionts. In contrast, polyphagous, holometabolous hosts provide the most variable endosymbiotic environment. In this work, I examined the interactions between the polyphagous, holometabolous insect, Bactrocera oleae (Rossi), and the enteric gammaproteobacterium, Candidatus Erwinia dacicola, throughout host development. Candidatus Erwinia dacicola was found in the digestive system of all life stages of wild olive flies. PCR and microscopy demonstrated that Ca. Erwinia dacicola resided intracellularly in the gastric caeca of the larval midgut, but extracellularly in the lumen of the foregut and ovipositor diverticulum of adult flies. I document the widespread distribution and high frequency of Ca. Er. dacicola in ten populations of wild olive flies sampled in four countries (3 Old World and 1 New World). The relative abundance of the bacterium was highest in adults and less prevalent in the egg and pupal stages. Among adult flies, the bacterium was most common in ovipositing females. These results suggest that Ca. Er. dacicola is a persistent, autochthonous endosymbiont of the olive fly. Finally, mating initiation was examined to study the influence of Ca. Er. dacicola on mating between a laboratory and a wild population of olive flies from Israel. Behavioral differences between the two populations, not presence of the endosymbiont, explained mating initiation.

Most animals contain chronic microbial infections that inflict no harm on their hosts. Recently, the gut microflora of humans and other animals have been characterized. However, little is known about the forces that shape the diversity of these bacterial communities. In this work, comparative genomics was used to investigate the evolutionary dynamics of host-adapted bacterial communities, using Wolbachia infecting arthropods and Lactobacteria infecting bees as the main model systems. Wolbachia are maternally inherited bacteria that cause reproductive disorders in arthropods, such as feminization, male killing and parthenogenesis. These bacteria are difficult to study because they cannot be cultivated outside their hosts. We have developed a novel protocol employing multiple displacement amplification to isolate and sequence their genomes. Taxonomically, Wolbachia is classified into different supergroups. We have sequenced the genomes of Wolbachia strain wHa and wNo that belong to supergroup A and B, respectively, and are present as a double-infection in the fruit-fly Drosophila simulans. Together with previously published genomes, a supergroup comparison of strains belonging to supergroups A and B indicated rampant homologous recombination between strains that belong to the same supergroup but were isolated from different hosts. In contrast, we observed little recombination between strains of different supergroups that infect the same host. Likewise, phylogenetically distinct members of Lactic acid bacteria co-exist in the gut of the honeybee, Apis mellifera, without transfer of genes between phylotypes. Nor did we find any evidence of co-diversification between symbionts and hosts, as inferred from a study of 13 genomes of Lactobacillus kunkeei isolated from diverse bee species and different geographic origins. Although Lactobacillus kunkeii is the most frequently isolated strain from the honey stomach, we hypothesize that the primary niche is the beebread where the bacteria are likely to contribute to the fermentation process. In the human gut, the microbial community has been shown to interact with the immune system, and likewise the microbial communities associated with insects are thought to affect the health of their host. Therefore, a better understanding of the role and evolution of endosymbiotic communities is important for developing strategies to control the health of their hosts.

Introduction: This study investigates the role of Wolbachia bacteria in the pathogenesis of O. volvulus keratitis in a mouse model. Wolbachia bacteria are essential symbionts of most filarial nematodes of importance for mankind. Methods: Using a mouse model for river blindness in which soluble extracts of filarial nematodes are injected in the corneal stroma, changes in stromal thickness and haze of the cornea are observed by in vivo confocal microscopy, followed by immunohistochemical staining for neutrophils and PECAM-1, as well as ELISA of corneal chemokines. Reactions to filarial extracts containing Wolbachia are compared to those without the endosymbiont. Results: The approach of characterizing Wolbachia’s role in river blindness in this study is threefold. Firstly, Wolbachia-depleted extracts from doxycycline treated onchocerciasis patients led to a diminished inflammatory response in corneas of C57BL/6 mice compared to untreated, i.e. Wolbachia containing antigen. The decreased cell recruitment observed with doxycycline treated extracts involved neutrophils, but not eosinophils. This finding demonstrated that the presence of Wolbachia increases neutrophil recruitment. Secondly, extracts from Wolbachia-containing B. malayi revealed markedly more pathology than endosymbiont-free A. viteae antigen. This again pointed at the role of Wolbachia in development of disease. Thirdly, Toll-like Receptor 4 (TLR4) dependence was shown to exist for the inflammatory response to Wolbachia harboring O. volvulus antigen by looking at the corneal pathology in TLR4-mutant C3H/HeJ mice, compared to the wild-type C3H/HeN strain. Investigating further Wolbachia mediated mechanisms of neutrophil recruitment to the cornea, this study also showed that expression of the adhesion molecule PECAM-1 in limbal vessels, as well as upregulation of the CXC chemokines KC and MIP-2 were dependent on the presence of functional TLR4 and Wolbachia respectively. Conclusions: This study indicates that the innate immune system and Wolbachia endobacteria play an important role in the inflammatory response associated with the pathogenesis of onchocerca keratitis, suggesting a complete alteration in our understanding of the immunopathology of filariasis. / Einleitung: Diese Arbeit untersucht die Rolle des Bakteriums Wolbachia in der Pathogenese der Onchozerka volvulus Keratitis anhand eines Mausmodels. Wolbachia sind essentielle endosymbiontische Bakterien, die in den meisten Filariosen, die für die Menschheit von Bedeutung sind, existieren. Methoden: Mit Hilfe eines Mausmodels für die Flußblindheit, in dem lösliche Filarienextrakte in das korneale Stroma von Mäusen injiziert werden, lassen sich Veränderungen in der Stromadicke und –durchsichtigkeit mit in vivo konfokaler Mikroskopie beobachten, gefolgt von immunhistochemischer Färbung von Neutrophilen und PECAM-1, wie auch ELISA von kornealen Chemokinen. Dabei werden Entzündungsreaktionen nach Injektion von Filarienmaterial mit oder ohne Wolbachia verglichen. Resultate: Die Untersuchung von Wolbachia's Rolle in der Flußblindheit erfolgte in drei Schritten. Zunächst führte Antigenmaterial von Wolbachia-freien, mit Doxyzyklin behandelten Onchozerkosepatienten zu geringerer Entzündungsreaktion in der Kornea von C57BL/6 Mäusen verglichen mit Wolbachia-enthaltendem Material. Die verminderte Enzündungszellzahl bei Doxyzyklin-behandelten Extrakten umfasste Neutrophile, aber nicht Eosinophile Granulozyten. Die Anwesenheit von Wolbachia führt daher zu verstärkter Neutrophileneinwanderung. Zweitens erwiesen Wolbachia-enthaltende B. malayi Extrakte eine signifikant verstärkte korneale Pathologie verglichen mit Endosymbiont-freiem A. viteae Antigen. Dieses Ergebnis deutete erneut auf die Rolle von Wolbachia in der Krankheitsentstehung. Drittens wurde anhand von Toll-like Rezeptor 4 (TLR4) mutanten C3H/HeJ Mäusen gezeigt, dass die Entzündungsreaktion, die von Wolbachia-enthaltenden O. volvulus Extrakten hervorgerufen wird, von TLR4 abhängig ist. Weitere Untersuchungen Wolbachia-abhängiger Mechanismen der Neutrophileneinwanderung in die Kornea erwiesen, dass die Expression des Adhäsionsmoleküls PECAM-1 in limbischen Gefäßen, wie auch die Hochregulation der CXC Chemokine KC und MIP-2 von TLR4 und der Anwesenheit von Wolbachia abhängig sind. Konklusion: Diese Arbeit zeigt, dass das angeborene Immunsystem und Wolbachia eine wichtige Rolle in der Pathogenese der O. volvulus Keratitis spielen, was auf eine neue Verstehensweise der Filariosenimmunpathologie hinweist.

Wolbachia é um gênero de bactérias endossimbiontes que são verticalmente transmitidas pelas fêmeas aos seus descendentes, embora transmissão entre táxons distintos também ocorra com certa freqüência. Entre os efeitos que essa bactéria causa nos sistemas de reprodutivos de seus hospedeiros destaca-se a incompatibilidade citoplasmática (IC). Wolbachia foi descrita em numerosas espécies de artrópodos, especialmente os insetos. Dentre os insetos, essa bactéria foi descrita em diversos gêneros das moscas-das-frutas da familia Tephritidae, tendo sido demonstrada a IC em Rhagoletis cerasi e Ceratitis capitata. Recentemente, essas bactérias foram identificadas nas moscas-das-frutas do gênero Anastrepha. No presente trabalho, procurou-se demonstrar se a Wolbachia estaria relacionada a IC entre Anastrepha sp.1 aff. fraterculus e Anastrepha obliqua. A amplificação e o seqüenciamento do gene wsp revelou que as populações das duas espécies, mantidas no laboratório, estavam infectadas por Wolbachia. A presença da bactéria foi, também, demonstrada citologicamente em embriões corados pelo DAPI, tendo-se, além disso, observado que elas se distribuem nos embriões em gradiente decrescente do pólo posterior para o anterior. Para testar a hipótese de que a bactéria é a causa da IC, foram estabelecidas populações das duas espécies onde a Wolbachia (e possivelmente outras bactérias não identificadas) foram eliminadas por tratamento térmico (30oC) aplicado às pupas. As taxas de eclosão de larvas nas progênies de cruzamentos entre indivíduos curados, foram menores que a eclosão nos cruzamentos entre indivíduos infectados, mas o tratamento não alterou a proporção sexual dos adultos. Cruzamentos intra-específicos entre indivíduos infectados e curados, produziu assimetria nas progênies dos cruzamentos recíprocos, ou seja, quando os fêmeas eram curadas e os machos infectados a taxa de eclosão foi significativamente menor que nos cruzamentos recíprocos demonstrando, assim, a existência de IC unidirecional nos cruzamentos dessas duas espécies de Anastrepha. Nesses cruzamentos, a proporção sexual das progênies adultas não divergiu significativamente do 1:1 esperado. Nas progênies híbridas de cruzamentos interespecíficos entre indivíduos infectados, observou-se um decréscimo significativo nas taxas de eclosão e alteração na proporção sexual entre os adultos, de acordo com a regra de Haldane. Quando as fêmeas eram de A. sp.1, as progênies eram constituídas apenas por fêmeas e quando eram de A. obliqua, machos também foram produzidos, mas em frequências menores que o esperado. Resultados similares foram obtidos quando indivíduos curados foram cruzados entre si. Cruzamentos interespecíficos de indivíduos infectados cruzados com indivíduos curados, produziram progênies com taxas de eclosão muito reduzidas e menores quando as fêmeas eram de A. sp.1 (infectadas ou curadas), do que nos cruzamentos onde as fêmeas eram de A. obliqua (infectadas ou não). Nestes últimos, quando a fêmea era infectada e os machos curados, a taxa de eclosão foi maior que no cruzamento recíproco, demonstrando a presença de IC entre as duas espécies. A proporção sexual também foi alterada nesses cruzamentos, segundo a regra de Haldane. Os resultados do presente trabalho demonstram, pela primeira vez, que a incompatibilidade citoplasmática mediada pela Wolbachia, ocorre nas duas espécies de Anastrepha e sugerem que deve existir uma interação entre a bactéria e os genomas das espécies hospedeiras. / The endosymbiont bacteria Wolbachia are vertically transmitted by the females to its progenies, although horizontal transmission between distinct taxa is also known. One of the most relevant effects caused by these bacteria in the reproductive behavior of its hosts is the cytoplasmic incompatibility (CI). Wolbachia was described in several groups of arthropods, in the insects including several genera of the tefritid fruit flies. Wolbachia-induced CI was reported in Rhagoletis cerasi and Ceratitis capitata. Recently, occurrence of these bacteria was described in several species of genus Anastrepha. Search for possible Wolbachia-induced CI in crosses of Anastrepha obliqua and A. sp.1 aff. fraterculus was the aim of the present study. Amplification and sequencing of the gene wsp of Wolbachia revealed that laboratory colonies of both species were infected with this bacteria. Cytological analysis of embryos stained with DAPI showed a multitude of bacteria distributed in decreasing gradients from the posterior to the anterior pole of the embryos. The hypothesis that there is CI between the two host species was tested using infected and cured individuals. The bacteria were removed by treating the pupae at the temperature of 30o C. Rate of egg hatch in progenies recovered from crosses of cured flies were lower than egg hatch in crosses of the infected strains, but no sex-ratio deviation from the expected 1:1 was observed. Intra-specific crosses between infected and cured individuals resulted in asymmetries in the progenies of reciprocal crosses. The egg hatch in crosses of cured obliqua females to infected sp.1 males was lower than in the reciprocal crosses, clearly indicating the presence of Wolbachia-induced CI in Anastrepha. In these crosses, sex-ratio among the adults does not deviate from the 1:1 ratio. In the hybrid progenies of inter-specific crosses, it was observed a decrease in the egg hatch rate, and deviation from 1:1 in the adult sex-ratio according to the Haldanes rule. From crosses of sp.1 females to obliqua males, only females were recovered while in crosses of obliqua females to sp.1 males, males were also produced but in lower frequencies than expected. Similar results were obtained when cured individuals were crossed. Very low egg hatch rates were observed in inter-specific crosses of infected to cured individuals, when sp.1 females (infected or cured) were used. In crosses of obliqua females (infected or cured), higher egg hatch rate was observed. Egg hatch was larger in crosses of infected female to cured males than in the reciprocal crosses, indicating a Wolbachia-induced IC between the two species of Anastrepha. The sex-ratios were also according to the Haldanes rule. This is the first report of Wolbachia-induced CI in Anastrepha. The existence of a possible interaction between the bacteria and the genomes of the host species is also suggested.

Les bactéries intracellulaires Wolbachia ont développé une vaste gamme d’interactions symbiotiques, du parasitisme reproductif au mutualisme chez les arthropodes terrestres et les nématodes filaires, devenant ainsi les endosymbiotes les plus répandus sur terre. Bien qu’elles se développent lentement dans les cultures cellulaires d’insectes pour lesquelles les marqueurs sont limités et qu’elles ne sont génétiquement pas manipulables, il existe un intéret croissant de déchiffrer leur mode de vie intracellulaire pour 2 raisons. Premièrement, Wolbachia intervient dans le développement et la transmission des arbovirus et deuxièmement, les filarioses lymphatiques sont traitables grâce à la susceptibilité des Wolbachia qui infectent les nématodes filaires aux antibiotiques. Au début de ce projet, j’ai infecté 2 lignées cellulaires de Drosophila melanogaster qui sont transcriptomiquement divergentes par une même souche de Wolbachia pouvant naturellement infecter Drosophila melanogaster. J’ai utilisé ces 2 lignées cellulaires qui sont différentiellement permissive à l’infection pour explorer l’interaction de Wolbachia avec le réticulum endoplasmique. Les observations par microscopie à fluorescence en temps réel et par microscopie électronique prouvent que cet organite est une source de membranes pour Wolbachia et possiblement, une source de nutriments. Pourtant, les analyses d’expression génique et les approches d’immunofluorescence démontrent que Wolbachia n’induit ni un stress au niveau du réticulum endoplasmique ni une protéolyse via la voie de signalisation ERAD suggérant dès lors, que Wolbachia subvertissent d’autres mécanismes pour assurer leur besoin en acides aminés. Au cours de ce projet, j’ai commencé à mettre en place une technique pour transformer Wolbachia par biolistique. La validation de cette technique de transformation a ouvert la voie vers l’optimisation de la procédure de sélection des transformants pour enfin pouvoir génétiquement manipuler Wolbachia. / The intracellular bacteria Wolbachia have developed a wide range of symbiotic interactions, from being opportunistic reproductive parasites to mutualists with terrestrial arthropods and filarial nematode species, making them the most common endosymbionts on earth. The discovery that they interfere with arboviruses development and transmission by mosquito vectors and that filarial diseases can be cured by targeting Wolbachia, have created a strong interest in deciphering the mechanisms underlying their intracellular lifestyle. However, being obligate intracellular endosymbionts, Wolbachia remain genetically intractable. They grow slowly in insect cell cultures, for which markers are limited. Despite these obstacles, and to limit cell line-specific phenotypes, I chose to infect 2 Drosophila melanogaster cell lines presenting different sets of expressed genes, with a unique Wolbachia strain, naturally hosted by Drosophila melanogaster. Using these 2 cell lines that are differently permissive to the infection, I explored the interaction of Wolbachia with the endoplasmic reticulum (ER). Through fluorescence time-lapse confocal and electron microscopy observations, I provide strong evidence that this organelle is the source of membrane for Wolbachia, and possibly a source of nutrients. However, gene expression analyses and immunofluorescence approaches demonstrate that Wolbachia do not induce ER stress nor an increased ERAD- induced proteolysis, suggesting; unlike previously reported, that Wolbachia salvage amino acids by other subversion mechanisms. Additionally, I pioneered biolistic bombardement of Wolbachia-infected cells and the validation of this transformation technique has paved the way towards optimization of transformant selection steps and ultimately to the genetic engineering of Wolbachia.

Wolbachia é um gênero de bactérias endossimbiontes que são verticalmente transmitidas pelas fêmeas aos seus descendentes, embora transmissão entre táxons distintos também ocorra com certa freqüência. Entre os efeitos que essa bactéria causa nos sistemas de reprodutivos de seus hospedeiros destaca-se a incompatibilidade citoplasmática (IC). Wolbachia foi descrita em numerosas espécies de artrópodos, especialmente os insetos. Dentre os insetos, essa bactéria foi descrita em diversos gêneros das moscas-das-frutas da familia Tephritidae, tendo sido demonstrada a IC em Rhagoletis cerasi e Ceratitis capitata. Recentemente, essas bactérias foram identificadas nas moscas-das-frutas do gênero Anastrepha. No presente trabalho, procurou-se demonstrar se a Wolbachia estaria relacionada a IC entre Anastrepha sp.1 aff. fraterculus e Anastrepha obliqua. A amplificação e o seqüenciamento do gene wsp revelou que as populações das duas espécies, mantidas no laboratório, estavam infectadas por Wolbachia. A presença da bactéria foi, também, demonstrada citologicamente em embriões corados pelo DAPI, tendo-se, além disso, observado que elas se distribuem nos embriões em gradiente decrescente do pólo posterior para o anterior. Para testar a hipótese de que a bactéria é a causa da IC, foram estabelecidas populações das duas espécies onde a Wolbachia (e possivelmente outras bactérias não identificadas) foram eliminadas por tratamento térmico (30oC) aplicado às pupas. As taxas de eclosão de larvas nas progênies de cruzamentos entre indivíduos curados, foram menores que a eclosão nos cruzamentos entre indivíduos infectados, mas o tratamento não alterou a proporção sexual dos adultos. Cruzamentos intra-específicos entre indivíduos infectados e curados, produziu assimetria nas progênies dos cruzamentos recíprocos, ou seja, quando os fêmeas eram curadas e os machos infectados a taxa de eclosão foi significativamente menor que nos cruzamentos recíprocos demonstrando, assim, a existência de IC unidirecional nos cruzamentos dessas duas espécies de Anastrepha. Nesses cruzamentos, a proporção sexual das progênies adultas não divergiu significativamente do 1:1 esperado. Nas progênies híbridas de cruzamentos interespecíficos entre indivíduos infectados, observou-se um decréscimo significativo nas taxas de eclosão e alteração na proporção sexual entre os adultos, de acordo com a regra de Haldane. Quando as fêmeas eram de A. sp.1, as progênies eram constituídas apenas por fêmeas e quando eram de A. obliqua, machos também foram produzidos, mas em frequências menores que o esperado. Resultados similares foram obtidos quando indivíduos curados foram cruzados entre si. Cruzamentos interespecíficos de indivíduos infectados cruzados com indivíduos curados, produziram progênies com taxas de eclosão muito reduzidas e menores quando as fêmeas eram de A. sp.1 (infectadas ou curadas), do que nos cruzamentos onde as fêmeas eram de A. obliqua (infectadas ou não). Nestes últimos, quando a fêmea era infectada e os machos curados, a taxa de eclosão foi maior que no cruzamento recíproco, demonstrando a presença de IC entre as duas espécies. A proporção sexual também foi alterada nesses cruzamentos, segundo a regra de Haldane. Os resultados do presente trabalho demonstram, pela primeira vez, que a incompatibilidade citoplasmática mediada pela Wolbachia, ocorre nas duas espécies de Anastrepha e sugerem que deve existir uma interação entre a bactéria e os genomas das espécies hospedeiras. / The endosymbiont bacteria Wolbachia are vertically transmitted by the females to its progenies, although horizontal transmission between distinct taxa is also known. One of the most relevant effects caused by these bacteria in the reproductive behavior of its hosts is the cytoplasmic incompatibility (CI). Wolbachia was described in several groups of arthropods, in the insects including several genera of the tefritid fruit flies. Wolbachia-induced CI was reported in Rhagoletis cerasi and Ceratitis capitata. Recently, occurrence of these bacteria was described in several species of genus Anastrepha. Search for possible Wolbachia-induced CI in crosses of Anastrepha obliqua and A. sp.1 aff. fraterculus was the aim of the present study. Amplification and sequencing of the gene wsp of Wolbachia revealed that laboratory colonies of both species were infected with this bacteria. Cytological analysis of embryos stained with DAPI showed a multitude of bacteria distributed in decreasing gradients from the posterior to the anterior pole of the embryos. The hypothesis that there is CI between the two host species was tested using infected and cured individuals. The bacteria were removed by treating the pupae at the temperature of 30o C. Rate of egg hatch in progenies recovered from crosses of cured flies were lower than egg hatch in crosses of the infected strains, but no sex-ratio deviation from the expected 1:1 was observed. Intra-specific crosses between infected and cured individuals resulted in asymmetries in the progenies of reciprocal crosses. The egg hatch in crosses of cured obliqua females to infected sp.1 males was lower than in the reciprocal crosses, clearly indicating the presence of Wolbachia-induced CI in Anastrepha. In these crosses, sex-ratio among the adults does not deviate from the 1:1 ratio. In the hybrid progenies of inter-specific crosses, it was observed a decrease in the egg hatch rate, and deviation from 1:1 in the adult sex-ratio according to the Haldanes rule. From crosses of sp.1 females to obliqua males, only females were recovered while in crosses of obliqua females to sp.1 males, males were also produced but in lower frequencies than expected. Similar results were obtained when cured individuals were crossed. Very low egg hatch rates were observed in inter-specific crosses of infected to cured individuals, when sp.1 females (infected or cured) were used. In crosses of obliqua females (infected or cured), higher egg hatch rate was observed. Egg hatch was larger in crosses of infected female to cured males than in the reciprocal crosses, indicating a Wolbachia-induced IC between the two species of Anastrepha. The sex-ratios were also according to the Haldanes rule. This is the first report of Wolbachia-induced CI in Anastrepha. The existence of a possible interaction between the bacteria and the genomes of the host species is also suggested.