Host and symbiont genetic contributions to fitness in a Trichogramma-Wolbachia symbiosis.

The fitness effects associated with Wolbachia infection have wide-ranging ecological and evolutionary consequences for host species. How these effects are modulated by the relative influence of host and Wolbachia genomes has been described as a balancing act of genomic cooperation and conflict. For vertically transmitted symbionts, like cytoplasmic Wolbachia, concordant host-symbiont fitness interests would seem to select for genomic cooperation. However, Wolbachia's ability to manipulate host reproductive systems and distort offspring sex ratios presents an evolutionary conflict of interest with infected hosts. In the parthenogenesis-inducing (PI) form of Wolbachia found in many haplodiploid insects, Wolbachia fitness is realized through females and is enhanced by their feminization of male embryos and subsequent parthenogenetic reproduction. In contrast, as long as Wolbachia is not fixed in a population and sexual reproduction persists, fitness for the host species is realized through both male and female offspring production. How these cooperating and competing interests interact and the relative influence of host and Wolbachia genomes were investigated in the egg parasitoid Trichogramma kaykai, where Wolbachia infection has remained at a low frequency in the field. A factorial design in which laboratory cultures of Wolbachia-infected T. kaykai were cured and re-infected with alternative Wolbachia strains was used to determine the relative influence of host and Wolbachia genomes on host fitness values. Our results suggest fitness variation is largely a function of host genetic background, except in the case of offspring sex ratio where a significant interaction between host and Wolbachia genomes was found. We also find a significant effect associated with the horizontal transfer of Wolbachia strains, which we discuss in terms of the potential for coadaptation in PI-Wolbachia symbioses

Кенґірське повстання як прояв кризи радянської табірної системи

Автор досліджує причини та перебіг Кенґірського повстання 1954 р. Жорстоко придушений, цей виступ став проявом кризи радянського табірного режиму, спричинивши реорганізацію виправно-трудової системи у СРСР.Автор исследует причины и ход Кенгирского восстания 1954 г. Жестоко подавленное, выступление стало проявлением кризиса советского лагерного режима, ставши причиной реорганизации исправительно-трудовой системы в СССР.The author investigated the causes and course of Kenhir uprising of 1954, being cruelly suppressed it demonstrated the crisis of camp system of the USSR and caused reorganization of penitentiary system

Формирование и использование справочно-библиографического фонда научной библиотеки (на примере ГПНТБ СО РАН)

Over the years, a large amount of data has become available regarding the (Holocene) evolution of the Rhine-Meuse delta, the Netherlands. This dataset, that is a result of a long-standing effort of data collection by Utrecht University, most likely is without a counterpart anywhere else in the world. It is the aim of this book: * to give a state of the art overview of the palaeogeographic evolution of the Rhine-Meuse delta, with an emphasis on the Holocene evolution; * to present the Holocene geology and palaeogeography in new detailed maps; * to present the 14C and other data that were used to determine the ages of the Holocene channel belts; * to make available many details of the work that has been carried out in the Rhine-Meuse delta to a larger (and international) audience. In Chapter 5, section 5.1 The geological-geomorphological map and palaeogeographic maps of the Rhine-Meuse delta, gives some technical information about the geological-geomorphological map (Addendum 1), the series of palaeogeographical maps (Addendum 2) and the GIS of the channel belt fragments that underlies it. In section 5.2 the longitidunal (w-e) cross-section of the delta is briefly explained, as well as the way in which it was constructed. The geological-geomorphological maps shows the ages of the Holocene channel belts, organized in 500 yr time intervals. The palaeogeographic maps siers shows the development of the channel belt network of the delta, based on the age determinations of the channel belts. The maps of are believed to be accurate to within ±200 yr, based on mapping and 14C dating. All radiocarbon dates that are used to construct the map, and that are of geological interest are incorporated in Appendix 1 and 2. In Appendix 3 details of the various channel belts indicated on the map are given, including dating evidence and references. Appendix 4 summarizes dating results, both as 14C ages and as calendar year ages (calibrated 14C ages). [Abstract based on chapter 10 Summary, in Berendsen & Stouthamer 2001

Intragenomic conflict in populations infected by Parthenogenesis Inducing Wolbachia ends with irreversible loss of sexual reproduction

<p>Abstract</p> <p>Background</p> <p>The maternally inherited, bacterial symbiont, parthenogenesis inducing (PI) <it>Wolbachia</it>, causes females in some haplodiploid insects to produce daughters from both fertilized and unfertilized eggs. The symbionts, with their maternal inheritance, benefit from inducing the production of exclusively daughters, however the optimal sex ratio for the nuclear genome is more male-biased. Here we examine through models how an infection with PI-<it>Wolbachia </it>in a previously uninfected population leads to a genomic conflict between PI-<it>Wolbachia </it>and the nuclear genome. In most natural populations infected with PI-<it>Wolbachia </it>the infection has gone to fixation and sexual reproduction is impossible, specifically because the females have lost their ability to fertilize eggs, even when mated with functional males.</p> <p>Results</p> <p>The PI <it>Wolbachia </it>infection by itself does not interfere with the fertilization process in infected eggs, fertilized infected eggs develop into biparental infected females. Because of the increasingly female-biased sex ratio in the population during a spreading PI-<it>Wolbachia </it>infection, sex allocation alleles in the host that cause the production of more sons are rapidly selected. In haplodiploid species a reduced fertilization rate leads to the production of more sons. Selection for the reduced fertilization rate leads to a spread of these alleles through both the infected and uninfected population, eventually resulting in the population becoming fixed for both the PI-<it>Wolbachia </it>infection and the reduced fertilization rate. Fertilization rate alleles that completely interfere with fertilization ("virginity alleles") will be selected over alleles that still allow for some fertilization. This drives the final resolution of the conflict: the irreversible loss of sexual reproduction and the complete dependence of the host on its symbiont.</p> <p>Conclusions</p> <p>This study shows that dependence among organisms can evolve rapidly due to the resolution of the conflicts between cytoplasmic and nuclear genes, and without requiring a mutualism between the partners.</p

Developmental succession of the microbiome of Culex mosquitoes

Background: The native microflora associated with mosquitoes have important roles in mosquito development and vector competence. Sequencing of bacterial V3 region from 16S rRNA genes across the developmental stages of Culex mosquitoes (early and late larval instars, pupae and adults) was used to test the hypothesis that bacteria found in the larval stage of Culex are transstadially transmitted to the adult stage, and to compare the microbiomes of field-collected versus laboratory-reared mosquitoes.Results: Beta diversity analysis revealed that bacterial community structure differed among three life stages (larvae, pupae and adults) of Culex tarsalis. Although only similar to 2 % of the total number of bacterial OTUs were found in all stages, sequences from these OTUs accounted for nearly 82 % of the total bacterial sequences recovered from all stages. Thorsellia (Gammaproteobacteria) was the most abundant bacterial taxon found across all developmental stages of field-collected Culex mosquitoes, but was rare in mosquitoes from laboratory-reared colonies. The proportion of Thorsellia sequences in the microbiomes of mosquito life stages varied ontogenetically with the greatest proportions recovered from the pupae of C. tarsalis and the lowest from newly emerged adults. The microbiome of field-collected late instar larvae was not influenced significantly by differences in the microbiota of the habitat due to habitat age or biopesticide treatments. The microbiome diversity was the greatest in the early instar larvae and the lowest in laboratory-reared mosquitoes.Conclusions: Bacterial communities in early instar C. tarsalis larvae were significantly more diverse when compared to late instar larvae, pupae and newly emerged adults. Some of the bacterial OTUs found in the early instar larvae were also found across developmental stages. Thorsellia dominated the bacterial communities in field-collected immature stages but occurred at much lower relative abundance in adults. Differences in microbiota observed in larval habitats did not influence bacterial community profiles of late instar larvae or adults. However, bacterial communities in laboratory-reared C. tarsalis larvae differed significantly from the field. Determining the role of Thorsellia in mosquitoes and its distribution across different species of mosquitoes warrants further investigation

Transcriptome Sequencing Reveals Novel Candidate Genes for Cardinium hertigii-Caused Cytoplasmic Incompatibility and Host-Cell Interaction

Cytoplasmic incompatibility (CI) is an intriguing, widespread, symbiont-induced reproductive failure that decreases offspring production of arthropods through crossing incompatibility of infected males with uninfected females or with females infected with a distinct symbiont genotype. For years, the molecular mechanism of CI remained unknown. Recent genomic, proteomic, biochemical, and cell biological studies have contributed to understanding of CI in the alphaproteobacterium Wolbachia and implicate genes associated with the WO prophage. Besides a recently discovered additional lineage of alphaproteobacterial symbionts only moderately related to Wolbachia, Cardinium (Bacteroidetes) is the only other symbiont known to cause CI, and genomic evidence suggests that it has very little homology with Wolbachia and evolved this phenotype independently. Here, we present the first transcriptomic study of the CI Cardinium strain cEper1, in its natural host, Encarsia suzannae, to detect important CI candidates and genes involved in the insect-Cardinium symbiosis. Highly expressed transcripts included genes involved in manipulating ubiquitination, apoptosis, and host DNA. Female-biased genes encoding ribosomal proteins suggest an increase in general translational activity of Cardinium in female wasps. The results confirm previous genomic analyses that indicated that Wolbachia and Cardinium utilize different genes to induce CI, and transcriptome patterns further highlight expression of some common pathways that these bacteria use to interact with the host and potentially cause this enigmatic and fundamental manipulation of host reproduction

Antibiotic treatment leads to the elimination of Wolbachia endosymbionts and sterility in the diplodiploid collembolan Folsomia candida

<p>Abstract</p> <p>Background</p> <p><it>Wolbachia </it>is an extremely widespread bacterial endosymbiont of arthropods and nematodes that causes a variety of reproductive peculiarities. Parthenogenesis is one such peculiarity but it has been hypothesised that this phenomenon may be functionally restricted to organisms that employ haplodiploid sex determination. Using two antibiotics, tetracycline and rifampicin, we attempted to eliminate <it>Wolbachia </it>from the diplodiploid host <it>Folsomia candida</it>, a species of springtail which is a widely used study organism.</p> <p>Results</p> <p>Molecular assays confirmed that elimination of <it>Wolbachia </it>was successfully achieved through continuous exposure of populations (over two generations and several weeks) to rifampicin administered as 2.7% dry weight of their yeast food source. The consequence of this elimination was total sterility of all individuals, despite the continuation of normal egg production.</p> <p>Conclusion</p> <p>Microbial endosymbionts play an obligatory role in the reproduction of their diplodiploid host, most likely one in which the parthenogenetic process is facilitated by <it>Wolbachia</it>. A hitherto unknown level of host-parasite interdependence is thus recorded.</p