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Ellegaard K.M.,Uppsala University | Klasson L.,Uppsala University | Naslund K.,Uppsala University | Bourtzis K.,University of Western Greece | And 3 more authors.
PLoS Genetics | Year: 2013

The importance of host-specialization to speciation processes in obligate host-associated bacteria is well known, as is also the ability of recombination to generate cohesion in bacterial populations. However, whether divergent strains of highly recombining intracellular bacteria, such as Wolbachia, can maintain their genetic distinctness when infecting the same host is not known. We first developed a protocol for the genome sequencing of uncultivable endosymbionts. Using this method, we have sequenced the complete genomes of the Wolbachia strains wHa and wNo, which occur as natural double infections in Drosophila simulans populations on the Seychelles and in New Caledonia. Taxonomically, wHa belong to supergroup A and wNo to supergroup B. A comparative genomics study including additional strains supported the supergroup classification scheme and revealed 24 and 33 group-specific genes, putatively involved in host-adaptation processes. Recombination frequencies were high for strains of the same supergroup despite different host-preference patterns, leading to genomic cohesion. The inferred recombination fragments for strains of different supergroups were of short sizes, and the genomes of the co-infecting Wolbachia strains wHa and wNo were not more similar to each other and did not share more genes than other A- and B-group strains that infect different hosts. We conclude that Wolbachia strains of supergroup A and B represent genetically distinct clades, and that strains of different supergroups can co-exist in the same arthropod host without converging into the same species. This suggests that the supergroups are irreversibly separated and that barriers other than host-specialization are able to maintain distinct clades in recombining endosymbiont populations. Acquiring a good knowledge of the barriers to genetic exchange in Wolbachia will advance our understanding of how endosymbiont communities are constructed from vertically and horizontally transmitted genes. © 2013 Ellegaard et al. Source


Viazis N.,Evangelismos Hospital | Keyoglou A.,Evangelismos Hospital | Kanellopoulos A.K.,Biomedical Science Research Center Al Fleming | Karamanolis G.,National and Kapodistrian University of Athens | And 4 more authors.
American Journal of Gastroenterology | Year: 2012

Objectives:Ambulatory 24-h pHimpedance monitoring can be used to assess the relationship of persistent symptoms and reflux episodes, despite proton pump inhibitor (PPI) therapy. Using this technique, we aimed to identify patients with hypersensitive esophagus and evaluate the effect of selective serotonin reuptake inhibitors (SSRIs) on their symptoms. Methods: Patients with normal endoscopy and typical reflux symptoms (heartburn, chest pain, and regurgitation), despite PPI therapy twice daily, underwent 24-h pHimpedance monitoring. Distal esophageal acid exposure (% time pH 4) was measured and reflux episodes were classified into acid or non-acid. A positive symptom index (SI) was declared if at least half of the symptom events were preceded by reflux episodes. Patients with a normal distal esophageal acid exposure time, but with a positive SI were classified as having hypersensitive esophagus and were randomized to receive citalopram 20 mg or placebo once daily for 6 months. Results: A total of 252 patients (150 females (59.5%); mean age 55 (range 1875) years) underwent 24-h pHimpedance monitoring. Two hundred and nineteen patients (86.9%) recorded symptoms during the study day, while 105 (47.9%) of those had a positive SI (22 (20.95%) with acid, 5 (4.76%) with both acid and non-acid, and 78 (74.29%) with non-acid reflux). Among those 105 patients, 75 (71.4%) had normal distal esophageal acid exposure time and were randomized to receive citalopram 20 mg (group A, n39) or placebo (group B, n36). At the end of the follow-up period, 15 out of the 39 patients of group A (38.5%) and 24 out of the 36 patients of group B (66.7%) continue to report reflux symptoms (P0.021). Conclusions: Treatment with SSRIs is effective in a select group of patients with hypersensitive esophagus. © 2012 by the American College of Gastroenterology. Source


Doudoumis V.,University of Ioannina | Doudoumis V.,University of Western Greece | Tsiamis G.,University of Ioannina | Tsiamis G.,University of Western Greece | And 15 more authors.
BMC Microbiology | Year: 2012

Background: Wolbachia is a genus of endosymbiotic -Proteobacteria infecting a wide range of arthropods and filarial nematodes. Wolbachia is able to induce reproductive abnormalities such as cytoplasmic incompatibility (CI), thelytokous parthenogenesis, feminization and male killing, thus affecting biology, ecology and evolution of its hosts. The bacterial group has prompted research regarding its potential for the control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. Results: In the present study, we employed a Wolbachia specific 16S rRNA PCR assay to investigate the presence of Wolbachia in six different laboratory stocks as well as in natural populations of nine different Glossina species originating from 10 African countries. Wolbachia was prevalent in Glossina morsitans morsitans, G. morsitans centralis and G. austeni populations. It was also detected in G. brevipalpis, and, for the first time, in G. pallidipes and G. palpalis gambiensis. On the other hand, Wolbachia was not found in G. p. palpalis, G. fuscipes fuscipes and G. tachinoides. Wolbachia infections of different laboratory and natural populations of Glossina species were characterized using 16S rRNA, the wsp (Wolbachia Surface Protein) gene and MLST (Multi Locus Sequence Typing) gene markers. This analysis led to the detection of horizontal gene transfer events, in which Wobachia genes were inserted into the tsetse flies fly nuclear genome. Conclusions: Wolbachia infections were detected in both laboratory and natural populations of several different Glossina species. The characterization of these Wolbachia strains promises to lead to a deeper insight in tsetse flies-Wolbachia interactions, which is essential for the development and use of Wolbachia-based biological control methods. © 2012 Doudoumis et al; licensee BioMed Central Ltd. Source


Abd-Alla A.M.M.,International Atomic Energy Agency | Bergoin M.,Montpellier University | Parker A.G.,International Atomic Energy Agency | Vlak J.M.,Wageningen University | And 4 more authors.
Journal of Invertebrate Pathology | Year: 2013

Tsetse flies (Diptera: Glossinidae) are the cyclical vectors of the trypanosomes, which cause human African trypanosomosis (HAT) or sleeping sickness in humans and African animal trypanosomosis (AAT) or nagana in animals. Due to the lack of effective vaccines and inexpensive drugs for HAT, and the development of resistance of the trypanosomes against the available trypanocidal drugs, vector control remains the most efficient strategy for sustainable management of these diseases. Among the control methods used for tsetse flies, Sterile Insect Technique (SIT), in the frame of area-wide integrated pest management (AW-IPM), represents an effective tactic to suppress and/or eradicate tsetse flies. One constraint in implementing SIT is the mass production of target species. Tsetse flies harbor obligate bacterial symbionts and salivary gland hypertrophy virus which modulate the fecundity of the infected flies. In support of the future expansion of the SIT for tsetse fly control, the Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture implemented a six year Coordinated Research Project (CRP) entitled " Improving SIT for Tsetse Flies through Research on their Symbionts and Pathogens" . The consortium focused on the prevalence and the interaction between the bacterial symbionts and the virus, the development of strategies to manage virus infections in tsetse colonies, the use of entomopathogenic fungi to control tsetse flies in combination with SIT, and the development of symbiont-based strategies to control tsetse flies and trypanosomosis. The results of the CRP and the solutions envisaged to alleviate the constraints of the mass rearing of tsetse flies for SIT are presented in this special issue. © 2013 International Atomic Energy Agency. Source


Brelsfoard C.,The New School | Brelsfoard C.,St. Catharine College | Tsiamis G.,University of Patras | Falchetto M.,University of Pavia | And 14 more authors.
PLoS Neglected Tropical Diseases | Year: 2014

Tsetse flies (Glossina spp.) are the cyclical vectors of Trypanosoma spp., which are unicellular parasites responsible for multiple diseases, including nagana in livestock and sleeping sickness in humans in Africa. Glossina species, including Glossina morsitans morsitans (Gmm), for which the Whole Genome Sequence (WGS) is now available, have established symbiotic associations with three endosymbionts: Wigglesworthia glossinidia, Sodalis glossinidius and Wolbachia pipientis (Wolbachia). The presence of Wolbachia in both natural and laboratory populations of Glossina species, including the presence of horizontal gene transfer (HGT) events in a laboratory colony of Gmm, has already been shown. We herein report on the draft genome sequence of the cytoplasmic Wolbachia endosymbiont (cytWol) associated with Gmm. By in silico and molecular and cytogenetic analysis, we discovered and validated the presence of multiple insertions of Wolbachia (chrWol) in the host Gmm genome. We identified at least two large insertions of chrWol, 527,507 and 484,123 bp in size, from Gmm WGS data. Southern hybridizations confirmed the presence of Wolbachia insertions in Gmm genome, and FISH revealed multiple insertions located on the two sex chromosomes (X and Y), as well as on the supernumerary B-chromosomes. We compare the chrWol insertions to the cytWol draft genome in an attempt to clarify the evolutionary history of the HGT events. We discuss our findings in light of the evolution of Wolbachia infections in the tsetse fly and their potential impacts on the control of tsetse populations and trypanosomiasis. © 2014 Brelsfoard et al. Source

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