Mutualism Breakdown by Amplification of Wolbachia Genes

Most insect species are associated with vertically transmitted endosymbionts. Because of the mode of transmission, the fitness of these symbionts is dependent on the fitness of the hosts. Therefore, these endosymbionts need to control their proliferation in order to minimize their cost for the host. The genetic bases and mechanisms of this regulation remain largely undetermined. The maternally inherited bacteria of the genus Wolbachia are the most common endosymbionts of insects, providing some of them with fitness benefits. In Drosophila melanogaster, Wolbachia wMelPop is a unique virulent variant that proliferates massively in the hosts and shortens their lifespan. The genetic bases of wMelPop virulence are unknown, and their identification would allow a better understanding of how Wolbachia levels are regulated. Here we show that amplification of a region containing eight Wolbachia genes, called Octomom, is responsible for wMelPop virulence. Using Drosophila lines selected for carrying Wolbachia with different Octomom copy numbers, we demonstrate that the number of Octomom copies determines Wolbachia titers and the strength of the lethal phenotype. Octomom amplification is unstable, and reversion of copy number to one reverts all the phenotypes. Our results provide a link between genotype and phenotype in Wolbachia and identify a genomic region regulating Wolbachia proliferation. We also prove that these bacteria can evolve rapidly. Rapid evolution by changes in gene copy number may be common in endosymbionts with a high number of mobile elements and other repeated regions. Understanding wMelPop pathogenicity and variability also allows researchers to better control and predict the outcome of releasing mosquitoes transinfected with this variant to block human vector-borne diseases. Our results show that transition from a mutualist to a pathogen may occur because of a single genomic change in the endosymbiont. This implies that there must be constant selection on endosymbionts to control their densities.FCT PhD fellowship: (SFRH/BD/51625/2011)

Wolbachia Variants Induce Differential Protection to Viruses in Drosophila melanogaster: A Phenotypic and Phylogenomic Analysis

Wolbachia are intracellular bacterial symbionts that are able to protect various insect hosts from viral infections. This tripartite interaction was initially described in Drosophila melanogaster carrying wMel, its natural Wolbachia strain. wMel has been shown to be genetically polymorphic and there has been a recent change in variant frequencies in natural populations. We have compared the antiviral protection conferred by different wMel variants, their titres and influence on host longevity, in a genetically identical D. melanogaster host. The phenotypes cluster the variants into two groups--wMelCS-like and wMel-like. wMelCS-like variants give stronger protection against Drosophila C virus and Flock House virus, reach higher titres and often shorten the host lifespan. We have sequenced and assembled the genomes of these Wolbachia, and shown that the two phenotypic groups are two monophyletic groups. We have also analysed a virulent and over-replicating variant, wMelPop, which protects D. melanogaster even better than the closely related wMelCS. We have found that a ~21 kb region of the genome, encoding eight genes, is amplified seven times in wMelPop and may be the cause of its phenotypes. Our results indicate that the more protective wMelCS-like variants, which sometimes have a cost, were replaced by the less protective but more benign wMel-like variants. This has resulted in a recent reduction in virus resistance in D. melanogaster in natural populations worldwide. Our work helps to understand the natural variation in wMel and its evolutionary dynamics, and inform the use of Wolbachia in arthropod-borne disease control.FCT PhD fellowship: (SFRH/BD/51625/2011), Royal Society University Research Fellowship

Genomic and environmental factors influence Wolbachia-Drosophila symbiosis

Intracellular, vertically transmitted bacteria form complex and intimate relationships with their hosts. Wolbachia, maternally transmitted α- proteobacteria, live within the cells of numerous arthropod species. Wolbachia are famous master manipulators of insect reproduction: to favour their own spread they can induce male killing, parthenogenesis or cytoplasmic incompatibility. Wolbachia can also protect various insects from pathogens, which makes them a promising tool for the control of vector-borne diseases. Mosquitoes with Wolbachia have already been released in the wild to eliminate dengue. Yet, how Wolbachia manipulate their hosts remains largely unknown.(...)Fundação para a Ciência e a Tecnologi

Generation of monoclonal cultures from Wolbachia-infected Drosophila melanogaster JW18 cell line

Cell lines are widely used models in biological research. They are particularly useful in studies of intracellular bacteria that cannot be efficiently propagated outside host organisms. Wolbachia, an intracellular symbiont of many invertebrates, induces strong reproductive and antiviral effects in its insect hosts. Wolbachia-infected insect cells have been widely used to study Wolbachia phenotypes. However, these cell lines often consist of mixed populations of cells with potentially varying phenotypes and responses to experimental treatments. In particular, cell lines with Wolbachia have been reported to exhibit variable growth rates and variable Wolbachia infection prevalence from one passage to the next. To remedy this, we generated monoclonal cell lines from the Wolbachia-infected Drosophila melanogaster-derived JW18 cell line. These clonal lines were established at different timepoints and show different Wolbachia infection statuses. This variability suggests that any treatment applied to a parental JW18 population could lead to the selection of sub-populations as opposed to influencing the physiology of the entire culture. Here, we present a protocol for generating single-cell clones and continuous clonal cultures from Wolbachia-infected insect cells, enabling more controlled and reproducible experiments

Epithelial‐specific knockout of the Rac1 gene leads to enamel defects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90135/1/j.1600-0722.2011.00904.x.pd

An empirical investigation into the determinants and persistence of different types of subjective well-being

A comparison of three measures of subjective well-being indicates two areas of difference. First, life evaluation is less dependent on external circumstances than evaluation of the past year. Temporary changes in health, labor market status and income have a smaller impact on life evaluation than on evaluation of the past year. Second, measures concerning the whole life exhibit a significant positive relation between current and past levels of well-being, but there is no such relation in case of evaluation of the past year. Moreover, external factors have a greater impact on the emotional dimension of life evaluation than on cognitive

The Influence of the Heating and Cooling Rates on the Temperature of the Phase Transitions

During the heat-treating processes (heating and cooling) of metal alloys phase transitions occur that affects their crystalline structure and properties. It is, therefore, important in metallurgy to know the exact transition temperature and the impact of these processes on the structure o the alloys. The aim of this research was to determine the influence of the heating and cooling rates on the temperature of phase transitions and to study how these processes proceed. Thermal analysis was carried out using Differential Scanning Calorimetry (DSC) in the heat flow regime. Two materials were investigated: eutectic alloy aluminum-silicon AK12 and aluminum-iron-manganese bronze BA1032. The following heating and cooling rates were used; 5, 10 and 15°C/min. Obtained results demonstrate that these rates strongly influence such transition parameters as: temperature, enthalpy and the heights of the peaks of the melting and crystallizationRobert Ulewic

An empirical investigation into the determinants and persistence of happiness and life evaluation

A comparison of measures of happiness and life evaluation indicates significant differences in correlates. Life evaluation is less dependent on external circumstances than happiness. Temporary changes in health, labour market status and income have a smaller impact on life evaluation than on happiness. Despite the differences both types of well-being exhibit a positive relation between current and past well-being. This result contradicts the hypothesis of general habituation

Przełomowe osiągnięcia lwowskich filologów w badaniach polskiego romantyzmu do roku 1939

The aim of the article is to show the exceptional merits of Polish Lviv-affiliated literary scholars in the study of Romanticism against the background of the achievements of scholars from other Polish universities. The analyzed problem covers the period until 1939, as this was when the Polish university in Lviv ceased to function. Interest in native Romanticism, especially in the three poet-prophets: Adam Mickiewicz, Juliusz Słowacki and Zygmunt Krasiński, was central to the work of positivist, Young-Poland and interwar-period philologists. The comparison of the achievements of Lviv with the “rest of Poland” includes monographs by the greatest authors along with their evaluation, dissertations and articles, as well as the methodology used in the research. During the Partitions of Poland (that is, until 1918), Polish studies experts from Lviv competed mainly with those from Kraków (Jagiellonian University) and several others from Warsaw. Most of the monographs on the three poet-prophets were written in Kraków, but it was in Lviv where Juliusz Kleiner wrote the best of them (on Krasiński). Kraków philologists would rely on an outdated methodology (they assessed literature on the basis of the ideological views of writers, without interpreting the works themselves). Meanwhile in Lviv, it was the text of the literary works and its artistic value that were mainly explored. Before 1914, Juliusz Kleiner developed a modern methodology (a literary work in the center of interest) and formulated the concept of the period of Romanticism that was later adopted by other scholars. Kleiner’s views became the basis for research into interwar literature. In the Second Polish Republic (1919–1939), there were six active universities: in Lviv, Kraków, Warsaw, Vilnius, Lublin, and Poznań. At that time, the field of Polish studies in Lviv was at its zenith, owing largely to the further outstanding achievements of Juliusz Kleiner, which were considered the best in Poland and timeless. They include, among others: two extensive monographs on Słowacki and Mickiewicz, the excellently compiled Complete Works of Juliusz Słowacki (most volumes), or the history of Polish literature released in Polish and German. In addition, Lviv was the place of work for Eugeniusz Kucharski, prominent expert on Aleksander Fredro in Poland, as well as for Konstanty Wojciechowski and Zygmunt Szweykowski, both eminent specialists in Polish novels. The city was also the place where the Adam Mickiewicz Literary Society was active since 1886 (it branched out into other cities after 1919) and the place of publication of Pamiętnik Literacki, the most distinguished literary research journal. Compared to other cities, Lviv gathered the largest group of scholars who studied Polish Romanticism and who devoted the greatest number of publications to it.Celem artykułu jest pokazanie wyjątkowych zasług polskich literaturoznawców związanych ze Lwowem w badaniach romantyzmu na tle osiągnięć uczonych z innych polskich uniwersytetów. Analizowany problem obejmuje okres do roku 1939, ponieważ dotąd funkcjonował we Lwowie polski uniwersytet. Zainteresowanie rodzimym romantyzmem, zwłaszcza trójcą wieszczów: Adamem Mickiewiczem, Juliuszem Słowackim i Zygmuntem Krasińskim, dominowało w pracach naukowych filologów epoki pozytywizmu, Młodej Polski i dwudziestolecia międzywojennego. Porównanie dorobku Lwowa z „resztą Polski” obejmuje monografie największych pisarzy i ich ocenę, rozprawy i artykuły oraz stosowaną w badaniach metodologię. W czasach zaborów (do 1918 r.) poloniści lwowscy konkurowali głównie z krakowskimi (UJ) i kilkoma z Warszawy. W Krakowie powstało najwięcej monografii trzech wieszczów, ale to we Lwowie Juliusz Kleiner napisał najlepszą (o Krasińskim). Filolodzy krakowscy stosowali przestarzałą metodologię (oceniali literaturę ze względu na poglądy ideologiczne pisarzy, nie interpretowali samych dzieł). We Lwowie badano głównie teksty utworów literackich, ich wartość artystyczną. Przed rokiem 1914 Juliusz Kleiner stworzył nowoczesną metodologię (dzieło literackie w centrum zainteresowań). Sformułował też pojęcie epoki romantyzmu, które przyswoili potem inni uczeni. Poglądy Kleinera stały się podstawą w badaniach literatury w dwudziestoleciu międzywojennym. W wolnej Polsce w latach 1919–1939 działało sześć uniwersytetów: we Lwowie, Krakowie, Warszawie, Wilnie, Lublinie i Poznaniu. Polonistyka we Lwowie przeżywała wtedy okres największej świetności. To kolejne zasługi wybitnego Juliusza Kleinera, uznawane za najlepsze w Polsce i ponadczasowe: dwie ogromne monografie – Słowackiego i Mickiewicza, znakomicie opracowane Dzieła wszystkie Słowackiego (większość tomów), historia literatury polskiej po polsku i niemiecku i inne. We Lwowie pracował Eugeniusz Kucharski – najlepszy w Polsce znawca Aleksandra Fredry; Konstanty Wojciechowski i Zygmunt Szweykowski – najwybitniejsi specjaliści od polskiej powieści. We Lwowie działało od 1886 r. Towarzystwo Literackie im. Adama Mickiewicza (w innych miastach po roku 1919 jego filie). Tam też ukazywał się „Pamiętnik Literacki” – najbardziej zasłużone czasopismo badaczy literatury. W porównaniu z pozostałymi miastami we Lwowie najliczniejsza grupa uczonych badała polski romantyzm i poświęciła mu najwięcej publikacji