Effects of shortened host life span on the evolution of parasite life history and virulence in a microbial host-parasite system

<p>Abstract</p> <p>Background</p> <p>Ecological factors play an important role in the evolution of parasite exploitation strategies. A common prediction is that, as shorter host life span reduces future opportunities of transmission, parasites compensate with an evolutionary shift towards earlier transmission. They may grow more rapidly within the host, have a shorter latency time and, consequently, be more virulent. Thus, increased extrinsic (i.e., not caused by the parasite) host mortality leads to the evolution of more virulent parasites. To test these predictions, we performed a serial transfer experiment, using the protozoan <it>Paramecium caudatum </it>and its bacterial parasite <it>Holospora undulata</it>. We simulated variation in host life span by killing hosts after 11 (<it>early </it>killing) or 14 (<it>late </it>killing) days post inoculation; after killing, parasite transmission stages were collected and used for a new infection cycle.</p> <p>Results</p> <p>After 13 cycles (≈ 300 generations), parasites from the <it>early-killing </it>treatment were less infectious, but had shorter latency time and higher virulence than those from the <it>late-killing </it>treatment. Overall, shorter latency time was associated with higher parasite loads and thus presumably with more rapid within-host replication.</p> <p>Conclusion</p> <p>The analysis of the means of the two treatments is thus consistent with theory, and suggests that evolution is constrained by trade-offs between virulence, transmission and within-host growth. In contrast, we found little evidence for such trade-offs across parasite selection lines within treatments; thus, to some extent, these traits may evolve independently. This study illustrates how environmental variation (experienced by the host) can lead to the evolution of distinct parasite strategies.</p

Niche-driven evolution of metabolic and life-history strategies in natural and domesticated populations of Saccharomyces cerevisiae

<p>Abstract</p> <p>Background</p> <p>Variation of resource supply is one of the key factors that drive the evolution of life-history strategies, and hence the interactions between individuals. In the yeast <it>Saccharomyces cerevisiae</it>, two life-history strategies related to different resource utilization have been previously described in strains from different industrial origins. In this work, we analyzed metabolic traits and life-history strategies in a broader collection of yeast strains sampled in various ecological niches (forest, human body, fruits, laboratory and industrial environments).</p> <p>Results</p> <p>By analysing the genetic and plastic variation of six life-history and three metabolic traits, we showed that <it>S. cerevisiae </it>populations harbour different strategies depending on their ecological niches. On one hand, the forest and laboratory strains, referred to as extreme "ants", reproduce quickly, reach a large carrying capacity and a small cell size in fermentation, but have a low reproduction rate in respiration. On the other hand, the industrial strains, referred to as extreme "grasshoppers", reproduce slowly, reach a small carrying capacity but have a big cell size in fermentation and a high reproduction rate in respiration. "Grasshoppers" have usually higher glucose consumption rate than "ants", while they produce lower quantities of ethanol, suggesting that they store cell resources rather than secreting secondary products to cross-feed or poison competitors. The clinical and fruit strains are intermediate between these two groups.</p> <p>Conclusions</p> <p>Altogether, these results are consistent with a niche-driven evolution of <it>S. cerevisiae</it>, with phenotypic convergence of populations living in similar habitat. They also revealed that competition between strains having contrasted life-history strategies ("ants" and "grasshoppers") seems to occur at low frequency or be unstable since opposite life-history strategies appeared to be maintained in distinct ecological niches.</p

How different anthropogenic environments have shaped the genome of S. cerevisiae ?

The yeast Saccharomyces cerevisiae plays an important role in food and beverage fermentations. In order to known how environmental constraints imposed by anthropogenic niches have shaped S. cerevisiae genomes and phenotypes, we sequenced the genome of 82 S. cerevisiae strains from various ecological origins. Using these genomic data, we found additional genetic elements acquired by introgression or by horizontal transfer. Here, we present two remarkable examples of divergent adaptation associated to yeast domestication for wine and milk fermentation. Firstly, we demonstrated the role of oligopeptide transporters encoded by FOT genes, which are recently acquired by wine yeasts from Torulaspora microellipsoides. These transporters with a broader specificity than S. cerevisiae dipeptides transporters, confer a strong competitive advantage during grape must fermentation and thus play a key role in the adaptation of wine yeasts to the nitrogen-limited wine fermentation environment. The genome of cheese strains, secondly, present some particular features. Genes of the GAL locus were replaced by their orthologues from a species apparently basal to the Saccharomyces clade. Allelic exchange of this locus in a wine strain enables improves growth speed in a media containing the two hexoses such as when released from the hydrolysis of lactose. In addition, a highly divergent high affinity transporter GAL2 and a specific allele of the regulator GAL80 were found. This work highlights the remarkable plasticity of yeast genomes as a mechanism of their adaptation to their environment

A influência do teatro no turismo em Curitiba

Orientador : Sandro Campos NevesMonografia (graduação) - Universidade Federal do Paraná, Setor de Ciências Humanas, Curso de Graduação em TurismoInclui referênciasResumo : O presente trabalho analisou o atual cenário de teatro em Curitiba e a influência exercida pelo Festival de Teatro de Curitiba no turismo da cidade. Para cumprir com o objetivo central, realizou-se pesquisa exploratória e bibliográfica, que fundamentaram o referencial teórico, dividido nos seguintes tópicos: turismo e cultura; eventos e turismo; teatro e festivais; festival de teatro de Curitiba; Espaço Positivo. Em seguida, foi aplicada a técnica de estudo de caso para o público presente na 27° edição do Festival, sendo a coleta de dados realizada por meio de questionários previamente estruturados, além de um roteiro de entrevista aplicado a gestora do Teatro Positivo, para compreender melhor a oferta da cidade. A análise dos dados coletados foi realizada por análise de conteúdo, onde as informações foram apresentadas através de gráficos e quadros, que auxiliaram na interpretação dos dados. As informações obtidas possibilitaram uma melhor interpretação da cena teatral de Curitiba, com foco no Festival de Teatro de Curitiba e no Teatro Positivo, objetos de estudo desse trabalho. Foi possível identificar que o teatro como influência para atrair a visita de turistas não é satisfatória, sendo a maior parte do público presente de Curitiba e região. Em resposta, propôs-se um projeto que utiliza uma estratégia de marketing online, através de mídias sociais, que consiste na elaboração de postagens em plataformas acessadas pelo público alvo do evento, com o objetivo de melhorar a divulgação, trazendo um número maior de visitantes.Abstract : The present paper analyzed the current theater scene in Curitiba and the influence exerted by the Festival de Teatro de Curitiba in the city tourism. In order to fulfill the central objective, an exploratory and bibliographical research was carried out, which based the theoretical reference, divided in the following topics: tourism and culture; events and tourism; theater and festivals; Festival de Teatro de Curitiba; Espaço Positivo. Then, the case study technique was applied to the audience present at the 27th Festival de Teatro de Curitiba, and the data collection was carried out through previously structured questionnaires, as well as an interview script applied to the Teatro Positivo manager, to understand better the offer of the city. The analysis of the collected data was performed by content analysis, where the information was presented through graphs and tables, which helped in the interpretation of the data. The information obtained allowed a better interpretation of the theatrical scene of Curitiba, focusing on the Festival de Teatro de Curitiba and Teatro Positivo, objects of study of this paper. It was possible to identify that the theater as an influence to attract the visit of tourists is not satisfactory, being the majority of the present public of Curitiba and region. In response, a project was proposed that uses an online marketing strategy, through social media, which consists in the elaboration of postings on platforms accessed by the target audience of the event, with the aim of improving the publicity, bringing a greater number of visitors

Artisanal and farmer bread making practices differently shape fungal species community composition in French sourdoughs

Preserving microbial diversity in food systems is one of the many challenges to be met to achieve food security and quality. Although industrialization led to the selection and spread of specific fermenting microbial strains, there are still ongoing artisanal processes that may allow the conservation of a wider species diversity and genetic diversity. We examined whether the diversity of artisanal practices could lead to an increased level in fungal species diversity for bread making. We used an interdisciplinary participatory research approach including bakers, psycho-sociologists and microbiologists to analyze French bread making practices and describe fungal communities in naturally fermented sourdough of 27 bakers and 12 farmer bakers. Bread making practices were classified in two groups: the farmer-like practice group and the artisanal-like practice group. The well-known bakery yeast, Saccharomyces cerevisiae, was dominant (i.e. with a relative abundance over 50%) in only 24% of sourdoughs while other yeast species, belonging to the Kazachstania genus, were dominant in 54% of sourdoughs. Bread making practices were found to drive the distribution of fungal species across sourdoughs. The most striking bread making practice effect was the occurrence of Kazachstania humilis in sourdoughs made with artisanal-like practices and the occurrence of Kazachstania bulderi in sourdoughs made with farmer-like practices. Phenotypic divergences between sourdough and non-sourdough strains were found for K. humilis but not for K. bulderi. Overall, our results showed that preserving bread making practice diversity allows the preservation of a higher species and phenotypic diversity in microbial communities

Écologie microbienne et ingénierie écologique

Cette HDR présente le travail de recherche de Thibault Nidelet qui a pour but de comprendre les propriétés émergentes des systèmes complexes et s’attache aujourd’hui plus spécifiquement à comprendre comment les interactions biotiques entre levures et entre levures et bactéries vont impacter les aliments fermentés. Cela se traduit par deux grandes questions : quels sont les mécanismes qui permettent au mélange d’être plus performant que des mono-cultures et comment peut-on exploiter ces mécanismes pour concevoir des starters de fermentation permettant de les piloter et d’améliorer la qualité finale des aliments fermentés ? Mes questions vont donc de l’écologie microbienne, jusqu’à l’écologie synthétique en passant par l'ingénierie écologique et l’évolution des communautés.valeurs et principes d'intégrité scientifique destinés à garantir le caractère honnête et scientifiquement rigoureux de tout travail de recherche, visés à l'article L.211-2 d

L'effet de la structuration spatiale et de l'hétérogénéité environnementale sur les interactions hôte-parasite (une approche d'évolution expérimentale et d'épidémiologie)

La majorité des environnements est spatialement structurée et hétérogène. De plus les organismes n évoluent pas seuls mais en interaction avec d autres organismes : leur évolution influence l évolution des autres organismes et inversement. C est dans ce contexte que nous avons étudié, grâce aux approches d épidémiologie et d évolution expérimentale, les interactions hôte-parasite entre la paramécie, Paramecium caudatum, et son parasite bactérien Holospora undulata. Dans une première série d expériences (Chapitre 3), nous avons exploré l évolution en métapopulation et la migration. Nous avons tout d abord montré que des patterns d adaptation locale pouvaient émerger en absence de coût et ce quand la réponse directe à la sélection est supérieure à la réponse indirecte. Nous avons aussi montré qu en fonction d interactions génotype x génotype le parasite pouvait influencer les patterns de dispersion soit en l augmentant soit en la diminuant. Ces deux résultats ont montré l importance dans l avenir d étudier la coévolution en métapopulation en présence de migration naturelle, les patterns de migration pouvant être amenés à évoluer sous l effet des interactions hôte-parasite. Nous nous sommes ensuite intéressés à l évolution de la virulence des parasites dans un milieu hétérogène pouvant modifier les traits d histoire de vie des hôtes (Chapitre 4). Nous avons montré, en accord avec les prédictions théoriques, qu une mortalité extrinsèque importante des hôtes sélectionnait les parasites les plus virulents et ce au temps de latence le plus court. Dans une autre expérience, nous avons favorisé, en modifiant les taux de croissance des hôtes, soit la transmission verticale soit la transmission horizontale. Les parasites où la transmission verticale a été favorisée ont évolué vers moins de virulence et plus d efficacité dans la transmission verticale. Les parasites où la transmission horizontale a été favorisée ont produit plus de formes infectieuses dédiées à la transmission horizontale. Pourtant, de façon surprenante, ce sont les parasites du traitement favorisant la transmission verticale qui ont produit les formes infectieuses les plus efficaces. Dans nos protocoles expérimentaux, nous n avons pas forcé l un des modes de transmission et c est cette plus grande liberté qui a permis de faire émerger cette corrélation positive entre les deux modes de transmission. Enfin, dans une dernière série d expériences nous avons étudié l effet de la température sur l interaction hôte-parasite (Chapitre 5). Nous avons montré que chez certaines combinaisons génotypiques d hôtes et de parasites, l infection permettait de mieux supporter les hautes températures. Cependant cet avantage ne favorisait pas l invasion des populations par le parasite. L origine de cette protection serait plutôt un effet indirect de l infection qui provoque chez l hôte une réaction de stress ayant notamment pour effet de protéger des températures élevées. Les parasites eux-mêmes n étant pas résistants aux hautes températures, ils peuvent donc être éliminés des hôtes infectés qui eux survivront grâce à la réponse au stress. L ensemble de ces expériences montre l impact important de l environnement sur l évolution de l interaction hôte parasite. Il souligne l intérêt d étudier la coévolution en métapopulation hétérogène avec migration naturelle.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Direct and correlated responses to selection in a host-parasite system: testing for the emergence of genotype specificity

Genotype × environment interactions can facilitate coexistence of locally adapted specialists. Interactions evolve if adaptation to one environment trades off with performance in others. We investigated whether evolution on one host genotype traded off with performance on others in long-term experimental populations of different genotypes of the protozoan Paramecium caudatum, infected with the bacterial parasite Holospora undulata. A total of nine parasite selection lines evolving on three host genotypes and the ancestral parasite were tested in a cross-infection experiment. We found that evolved parasites produced more infections than did the ancestral parasites, both on host genotypes they had evolved on (positive direct response to selection) and on genotypes they had not evolved on (positive correlated response to selection). On two host genotypes, a negative relationship between direct and correlated responses indicated pleiotropic costs of adaptation. On the third, a positive relationship suggested cost-free adaptation. Nonetheless, on all three hosts, resident parasites tended to be superior to the average nonresident parasite. Thus genotype specificity (i.e., patterns of local adaptation) may evolve without costs of adaptation, as long as direct responses to selection exceed correlated responses