Academic literature on the topic 'Eucaryotes unicellulaires'
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Journal articles on the topic "Eucaryotes unicellulaires":
Bornens, Michel. "Polarité cellulaire : sens et signification." médecine/sciences 35, no. 5 (May 2019): 452–61. http://dx.doi.org/10.1051/medsci/2019092.
Després, Merlin, and Simon Gaudin. "Le monoxyde d’azote: Une arme du système immunitaire pour brouiller les communications entre bactéries." médecine/sciences 36, no. 11 (November 2020): 1074–77. http://dx.doi.org/10.1051/medsci/2020214.
Dissertations / Theses on the topic "Eucaryotes unicellulaires":
Barbier, Michèle. "Regulation du cycle cellulaire chez les unicellulaires eucaryotes dinoflagelles." Paris 6, 1996. http://www.theses.fr/1996PA066463.
Rolland, Thomas. "Génomique comparative des levures hémiascomycètes : leçons tirées de l'évolution d'organismes unicellulaires eucaryotes." Paris 6, 2010. http://www.theses.fr/2010PA066515.
Monjot, Arthur. "Les eucaryotes unicellulaires dans les écosystèmes lacustres : de la diversité fonctionnelle aux interactions hôte-parasites." Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2023. http://www.theses.fr/2023UCFA0109.
Over the last few decades, our understanding of microbial diversity in the environment has advanced considerably, particularly with the advent of next-generation sequencing methods and -omics approaches. These methods have allowed for a more comprehensive evaluation of microbial diversity compared to traditional culture-based approaches. The most commonly used method for analyzing diversity is metabarcoding, which is based on the study of a unique and ubiquitous marker. This method has revealed a considerable and unsuspected diversity of microbial eukaryotes in aquatic environments. However, this approach is mainly descriptive and does not allow for the determination of the physiology or understanding of the role of these microorganisms in ecosystems. Other methods, such as metatranscriptomics, offer the possibility of studying their metabolic potential in relation to environmental parameters. Nevertheless, these high-throughput sequencing approaches lead to the production of a vast quantity of environmental sequences, most of which remain unknown. To better understand the diversity-function link within microbial eukaryotes and their role in lacustrine trophic networks, several approaches have been used.Metabarcoding coupled with a study of morpho-physio-phenotypic traits, metatranscriptomics and a methodology based on the isolation and characterization of host-parasite pairs (sequencing and in situ hybridization), were carried out on lake samples (Pavin, meromictic; Aydat, dimictic). These analyses revealed the high diversity of photo-osmo-phago-mixotrophs and parasites, while also highlighting the strong seasonal variations they undergo in the mixolimnion of lake Pavin. For example, periods of mixing benefiting photosynthetic host communities favor the development and dissemination of parasitic fungi, notably through the overexpression of genes involved in zoospore phototaxis and lipid metabolism. Among these parasitic fungi, Microsporidia are newly identified players in aquatic food webs. Indeed, we discovered a high prevalence (42.5%) host-parasite association between a potential new species of Microsporidia and a species of rotifer in lake Aydat. An important rare biosphere has also been highlighted in the anoxic monimolimnion of Lake Pavin, characterized by numerous saprotrophs overexpressing genes related to sulfur, nitrate, and organic matter degradation metabolisms. The characteristic metabolisms of organisms of different trophic modes have also been studied by constructing protein sequences similarity networks.While characterizing the majority of unknown sequences for the first time (>40%), we have revealed the genetic proximity of proteins between heterotrophic and photo-osmo-phago- mixotrophic microorganisms and between saprotrophs and parasites, as well as a relative functional redundancy of primary metabolisms. On the other hand, we have identified nearly one million proteins characteristic of a single functional group, which, for some, represent real prospects for studying the metabolic pathways involved in host-parasite interactions
Yang, Tié. "Caractérisation et expression de proto-oncogènes "Myb-like" chez les unicellulaires ciliés." Paris 11, 2002. http://www.theses.fr/2002PA112053.
In this thesis of PhD. ,two myb family genes were cloned and characterized in two ciliates species, Euplotes and Sterkiella ( Oxytricha, previously), respectively. The myb from Euplotes is nominated emyb1 and the one from Sterkiella (Oxytricha) is omyb1. Myb genes, are widely found in eucaryotic animals and plants. The myb genes were firstly identified in animals as proto-oncogenes which act as specific transcription regulators concerning cell proliferation and differentiation. In plants, myb gene products play roles in various cellular activities, including cellular metabolism, morphogenesis, tissue formation, cell proliferation and differentiation. The most characteristic feature of myb gene is that they carry several imperfect repeats about 50 amino acids, called myb motif, in for their DNA-binding domain. The repeat number of the myb motif is three in all species of animal kingdom and two (majority) or three (minority) in species of plant kingdom. The study of the two myb genes emyb1 and omyb1 revealed that in ciliates there exist both R2- and R3-myb genes. The emyb1 contains only two myb motif repeats and the omyb1 contains three. The phylogenic analyze showed that the two myb genes in ciliates pointed to same ancestral myb gene together with those in animal and plants. The expression level of emyb1 varied between vegetative and conjugating cells and between mature and immature cells. It suggested that this gene may function in regulation of cell cycle and in the controlling of cell maturation. Further study of antisense oligo-nucleotide manifested that the emyb1 participates in the development of macronucleus in conjugated cells. The omyb1 gene expression increased in starved cells implied that it may function in the reaction to deleterious condition and start the encystment phenomenon for the cell to pass the unfavorable period. Another transcription factor gene orpb9 was identified to coexist in the same minichromosome with the omyb1. This suggests biological significance in hypotrichous species that there may exist a molecular mechanism that genes coexist in the same minichromosome to facilitate the transcriptional regulation for the functional or/and quantitative coherency of related genes. Ciliates are a unicellular phylum, which is distinguished from the other eukaryotic species by one of the characters of nucleus dimorphism. The molecular mechanism of the regulation of gene transcription and cell cycle controlling of this unicellular phylum is little known. .
Viprey, Manon. "Phylogénie moléculaire et éléments de biogéographie de trois lignées importantes des communautés d’eucaryotes unicellulaires en milieu marin : les Chloroplastida, les Radiolaria et les Alveolata." Paris 6, 2008. http://www.theses.fr/2008PA066098.
Miot, Jennifer. "Processus microbiens de biominéralisation et de détoxification des métaux/métalloïdes : oxydation du fer par des bactéries anaérobies neutrophiles et résistance au fer et à l'arsenic chez des eucaryotes unicellulaires de drainages miniers acides." Paris 7, 2008. http://www.theses.fr/2008PA077228.
This work aimed at studying the response of microorganisms to toxic elements, such as arsenic and to the lethal effects of mineral precipitation within cellular structures. We applied microscopic and spectroscopic tools adapted to the study of these organic-mineral assemblages. In a first section, we studied two different bacterial strains, both using Fe(II) as an electron donor under strictly anoxic conditions at neutral pH. The phototrophic strain SW2 precipitated iron on lipo-polysaccharidic fibres only at distance from the cells, whereas the denitrifying strain BoFeNl precipitated iron within its periplasm. Ultrafine cellular structures and proteins were preserved within these encrusted cells that can be considered as microfossils. In a second section, we studied unicellular eukaryotes from a Fe and As-rich acid mine drainage. Iron accumulation within the cells was shown to be completely decoupled from the processes of arsenic detoxification. Arsenic detoxification starts with As(V) reduction to As(III), followed by its complexation by thiol groups, involving the glutathione pathway and leading to its export from the cell. However, we show that As(V) was more toxic to the cells than As(III). Our results altogether provide new insights on the mechanisms of microbial biomineralization and detoxification of metals/metalloids and opens new perspectives for the search of biosignatures of specific metabolisms
Brosson, Damien. "Analyse protéomique et caractérisation de nouvelles protéines de paroi chez Encephalitozoon cuniculi." Phd thesis, Clermont-Ferrand 2, 2006. http://tel.archives-ouvertes.fr/docs/00/68/86/92/PDF/2006CLF21636.pdf.
Guerin, Nina. "Acclimatation du pico-eucaryote photosynthétique Pelagomonas calceolata aux changements environnementaux." Electronic Thesis or Diss., université Paris-Saclay, 2023. https://www.biblio.univ-evry.fr/theses/2023/interne/2023UPASL138.pdf.
Photosynthetic picoeukaryotes (PPE) are abundant in all oceans and represent a significant proportion of biomass and primary production. Climate models predict an extension of oligotrophic areas in the following decades, which could greatly increase the abundance and ecological impact of PPEs. Among them, the microalga Pelagomonas calceolata (Stramenopiles/Pelagophyceae) is widely distributed in the oceans (Worden et al., 2012) but its role in the carbon cycle and its impact on the trophic chain remain poorly characterised (Dupont et al., 2015). In situ and in vitro analyses suggest that P. calceolata can adapt to environmental variations thanks to a significant capacity to modulate gene expression (Carradec et al., 2018; Dimier et al., 2009). The aim of this thesis is to understand how P. calceolata adapts to environmental variations in the many environments it lives in. In the first chapter, the P. calceolata genome is assembled, annotated and compared with those of other PPEs. Thanks to metagenomic and metatranscriptomic data from the Tara Oceans expedition, the biogeography and transcriptomic activity of P. calceolata under different environmental conditions has provided a better understanding of the present and future distribution of this alga, and the genes involved in its ecological success (Guérin et al 2022). In the second chapter, we focused on the acclimatisation habilites of P. calceolata to changing nitrogen quantities and sources. Differentially expressed genes (DEGs) in P. calceolata as a function of nitrate concentration in Tara Oceans samples were compared with those identified during growth experiments under controlled conditions. P. calceolata was grown in media depleted in nitrate or in which nitrate was replaced by ammonium, urea or cyanate. The comparison of DEGs obtained in the laboratory with those obtained from environmental data provides a better understanding of the metabolism of this microalga in the face of nitrate shortage, and of the mechanisms put in place in the environment to cope with variability in nitrate availability, in particular through its ability to use organic nitrogen sources. In the third chapter, we aimed to better understand how depth affects the physiology of P. calceolata. P. calceolata is found in water samples from the surface down to a depth of at least 200m. We found that sampling depth had a strong impact on the expression of P. calceolata genes involved in photorespiration and carbon concentration mechanisms. During this PhD thesis, the characterisation of the adaptive capacities of P. calceolata led to a better understanding of how transcriptomic regulation enables it to be cosmopolitan, and shows that this microalga can be used as a model organism thanks to the possibility of studying it simultaneously in the laboratory and in environmental multi-omics data