Foram utilizados quatro Novilhos nelore, com peso vivo médio de 190 ± 32 kg, canulados no rúmen num experimento com delineamento Quadrado Latino 4x4, onde o objetivo do trabalho foi avaliar o efeito da levedura, monensina e salinomicina sobre os parâmetros ruminais e o aparecimento de protozoários ciliados ruminais.O experimento foi executado no Campus Administrativo de Pirassununga, na Faculdade de Zootecnia e Engenharia de Alimentos da Universidade de São Paulo. A dieta oferecida aos animais foi composta por silagem de sorgo e concentrado (30:70), onde foram submetidos a quatro tratamentos diferidos de acordo com o aditivo usado, 5,0g de Levedura (Beef Sacc®), 0,42g de salinomicina (Coxistac®), 2,0g de monensina sódica (Rumensin®) e o controle sem aditivo. Os parâmetros avaliados foram degradabilidade ruminal, in situ do volumoso e da dieta total, concentração de ácidos graxos voláteis e nitrogênio amoniacal, pH ruminal, taxa de passagem líquida, turnover e volume ruminal, e identificação e contagem dos protozoários ciliados. O período experimental foi subdividido em vinte e um dias de adaptação e sete de colheita, totalizando vinte e oito dias por período experimental. Foram mensurados os coeficientes de degradabilidade nos períodos de incubação de 0, 3, 6, 12, 24, 48, 72 e 96 horas. Para a colheita de liquido ruminal foram utilizados os horários 0, 2, 4, 6, 8 horas; as colheitas de marcador de fase liquida (PEG) foram realizadas ás 0; 1,5; 3; 6; 12 e 24 horas após a alimentação. Houve aumento do valor para a fração “b" na MS, no tratamento levedura (p<0,05), e no tratamento salinomicina. Também houve uma tendência a aumentar a fração “b" no FDN. O tratamento levedura aumentou significativamente o número de protozoários ciliados no rúmen (p<0,05). Os valores referentes ao pH não foram afetados pelos tratamentos (p>0,05). A concentração de amônia e os valores encontrados para a cinética ruminal não foram afetados pelos tratamentos (p>0,05). O uso de ionóforos melhorou a proporção dos ácidos acético:propiônico, propiônico e butírico enquanto a levedura aumentou a concentração de acido acético (p<0,05). / Four Nelore Steers had been used, with average alive weight of 190 ± 32 kg, rumen cannulas, in an experiment with Squared delineation Latin 4x4, where the objective of the work was to evaluate the effect of the yeast culture, monensin and salinomycin on the rumen parameters and the appearance of ciliates protozoa. The experiment was executed in the Faculdade de Zootecnia e Engenharia de Alimentos of the Universidade de São Paulo. The diet offered to the animals was composed for ensilage and concentrated (30:70), where the four differed treatments had been submitted in accordance with the used additive, 5,0g of yeast culture (Beef Sacc), 0,42g of salinomycin (Coxistac), 2,0g of monensin (Rumensin) and the control without additive. The evaluated parameters had been ruminal degradability “in situ" of voluminous and the total diet, the concentration of volatile fatty acid concentration and ammoniac nitrogen concentration, pH ruminal, liquid passage, turnover and ruminal volume, and number and specie of ciliates protozoa. The experimental period was subdivided in twenty and one days of adaptation and seven of harvest, having totalized twenty and eight days for experimental period. The coefficients of degradability in the incubation periods of 0, 3, 6, 12, 24, 48, 72 and 96 hours had been measure. For the harvest of I eliminate ruminal had been used schedules 0, 2, 4, 6, 8 hours; the harvests of phase marker eliminate (PEG) had been carried through ace 0; 1,5; 3; 6; 12 and 24 hours after the feeding. It had increase of the value for fraction "b" in the MS, the treatment yeast culture, and the salinomycin treatment (p<0,05). Also it had a trend to increase fraction "b" in the FDN. The treatment yeast culture significantly increased the number of ciliates protozoa in rumen (p<0,05). The referring values to pH had not been affected by the treatments (p>0,05). The ammonia concentration and the values found for the kinetic ruminal had not been affected by the treatments (p>0,05). The use of ionophores improved the acid ratio of the acetic:propionic, propionic and butiric while the yeast culture increased the acids concentration of acetic (p<0,05).

Made available in DSpace on 2016-06-02T19:32:00Z (GMT). No. of bitstreams: 1 4171.pdf: 1651530 bytes, checksum: 8003a7d4f21e79f409398cd7ec50f25d (MD5) Previous issue date: 2012-02-13 / Universidade Federal de Minas Gerais / Bacteria, found in terrestrial and aquatic environments, besides their important role in organic matter decomposition and nutrient cycling, are a food source for organisms of the higher trophic levels in the food chain, such as protozooplanktonic and metazooplanktonic organisms. This study aimed to evaluate the relative importance of protozooplanktonic (ciliates and heterotrophic nanoflagellates) and metazooplanktonic organisms (rotifers, cladocerans and copepods) as bacterial consumers throughout a year, which included a rainy and a dry season, in a eutrophic environment (Monjolinho reservoir-SP) by quantifying their ingestion rates. For this purpose, grazing experiments were carried out bimonthly during one year at the sub-surface of a central station of the reservoir using fluorescently labeled bacteria (FLB) dyed with DTAF. In each survey, besides the experiments, limnological (pH, dissolved oxygen, temperature, conductivity, water transparency and nutrients) and biological (chlorophyll-a and phaeophytin concentrations, bacterioplankton, protozooplankton and metazooplankton density) water parameters were also sampled. The heterotrophic nanoflagellates (HNF) showed higher population ingestion rates than the ciliates in dry and rainy seasons, and the HNF smaller than 5&#956;m were the main consumers of bacteria. Among the metazooplanktonic organisms, the rotifers dominated the bacterial ingestion, and the organisms belonging to the genus Filinia and Keratella and to the families Testudinellidae and Brachionidae were the main bacterial consumers. Besides ingesting bacteria, however, protozoa and rotifers population also seemed to be controlled by cladocerans and copepods predation, which, in turn, seemed to be regulated by predation of larger organisms, such as small vertebrates. Thus, the predation control (top-down) occured both on bacterial communities and protozooplanktonic and metazooplanktnic communities and bacteria were regulated both by direct and indirect predation of zooplanktonic population. The resources control (bottom-up) semmed to be higher during the dry season, while in the rainy season bacterial communities were more controlled by predation. The greatest impact on bacterial communities was caused by HNF and ciliates during the rainy season and by HNF and rotifers during the dry one. / As bacterias, encontradas em ambientes terrestres e aquaticos, alem de possuirem importante papel na decomposicao da materia organica e na ciclagem de nutrientes, sao fonte de alimento para organismos de niveis troficos superiores, tais como protozoarios e organismos do metazooplancton. O presente trabalho avaliou a importancia relativa de organismos protozooplanctonicos e metazooplanctonicos (rotiferos, cladoceros e copepodes) como consumidores de bacterias em um ambiente eutrofico (Reservatorio do Monjolinho-SP) pela quantificacao das taxas de consumo durante o periodo de um ano, que englobou uma estacao seca e uma chuvosa. Para isso, na superficie de um ponto central no reservatorio, foram realizados experimentos de bacterivoria (grazing) bimestralmente durante um ano, utilizando bacterias marcadas fluorescentemente (FLB) com o corante DTAF. Nos dias dos experimentos foram tambem analisados parametros limnologicos (pH, oxigenio dissolvido, temperatura, condutividade, transparencia da agua, e nutrientes) e biologicos (concentracoes de clorofila-a e feofitina, densidade do bacterioplancton, protozooplancton e metazooplancton). Os nanoflagleados heterotroficos (NFH), quando comparados aos ciliados, apresentaram maiores taxas populacionais de ingestao de bacterias tanto no periodo seco quanto no chuvoso, sendo os NFH menores que 5 &#956;m os maiores consumidores de bacterias. Dentre os organismos metazooplanctonicos, os rotiferos dominaram o consumo de bacterias, sendo os representantes dos generos Filinia e Keratella e das familias Testudinellidae e Brachionidae os maiores consumidores de bacteria. Os dados obtidos indicaram que, alem de predadores de bacterias, as populacoes de protozoarios e rotiferos pareceram ser reguladas pela predacao de cladoceros e copepodes, os quais, por sua vez, parecem sofrer pressao de predacao por organismos maiores, como provavelmente pequenos vertebrados. Assim, o controle por predacao (top-down) ocorreu tanto sobre as comunidades bacterianas quanto sobre as protozooplanctonicas e metazooplanctonicas, sendo as comunidades bacterianas reguladas tanto pela predacao direta quanto indireta das populacoes zooplanctonicas. O controle por disponibilidade de recursos (bottom-up) pareceu ter maior influencia no reservatorio no periodo seco, enquanto no periodo chuvoso, as comunidades bacterianas pareceram mais controladas por predacao, sendo que maiores impactos sobre as comunidades bacterianas foram causados pelos NFH e ciliados no periodo chuvoso, e pelos NFH e rotiferos no periodo seco.

Foram utilizados quatro Novilhos nelore, com peso vivo médio de 190 ± 32 kg, canulados no rúmen num experimento com delineamento Quadrado Latino 4x4, onde o objetivo do trabalho foi avaliar o efeito da levedura, monensina e salinomicina sobre os parâmetros ruminais e o aparecimento de protozoários ciliados ruminais.O experimento foi executado no Campus Administrativo de Pirassununga, na Faculdade de Zootecnia e Engenharia de Alimentos da Universidade de São Paulo. A dieta oferecida aos animais foi composta por silagem de sorgo e concentrado (30:70), onde foram submetidos a quatro tratamentos diferidos de acordo com o aditivo usado, 5,0g de Levedura (Beef Sacc®), 0,42g de salinomicina (Coxistac®), 2,0g de monensina sódica (Rumensin®) e o controle sem aditivo. Os parâmetros avaliados foram degradabilidade ruminal, in situ do volumoso e da dieta total, concentração de ácidos graxos voláteis e nitrogênio amoniacal, pH ruminal, taxa de passagem líquida, turnover e volume ruminal, e identificação e contagem dos protozoários ciliados. O período experimental foi subdividido em vinte e um dias de adaptação e sete de colheita, totalizando vinte e oito dias por período experimental. Foram mensurados os coeficientes de degradabilidade nos períodos de incubação de 0, 3, 6, 12, 24, 48, 72 e 96 horas. Para a colheita de liquido ruminal foram utilizados os horários 0, 2, 4, 6, 8 horas; as colheitas de marcador de fase liquida (PEG) foram realizadas ás 0; 1,5; 3; 6; 12 e 24 horas após a alimentação. Houve aumento do valor para a fração “b” na MS, no tratamento levedura (p<0,05), e no tratamento salinomicina. Também houve uma tendência a aumentar a fração “b” no FDN. O tratamento levedura aumentou significativamente o número de protozoários ciliados no rúmen (p<0,05). Os valores referentes ao pH não foram afetados pelos tratamentos (p>0,05). A concentração de amônia e os valores encontrados para a cinética ruminal não foram afetados pelos tratamentos (p>0,05). O uso de ionóforos melhorou a proporção dos ácidos acético:propiônico, propiônico e butírico enquanto a levedura aumentou a concentração de acido acético (p<0,05). / Four Nelore Steers had been used, with average alive weight of 190 ± 32 kg, rumen cannulas, in an experiment with Squared delineation Latin 4x4, where the objective of the work was to evaluate the effect of the yeast culture, monensin and salinomycin on the rumen parameters and the appearance of ciliates protozoa. The experiment was executed in the Faculdade de Zootecnia e Engenharia de Alimentos of the Universidade de São Paulo. The diet offered to the animals was composed for ensilage and concentrated (30:70), where the four differed treatments had been submitted in accordance with the used additive, 5,0g of yeast culture (Beef Sacc), 0,42g of salinomycin (Coxistac), 2,0g of monensin (Rumensin) and the control without additive. The evaluated parameters had been ruminal degradability “in situ” of voluminous and the total diet, the concentration of volatile fatty acid concentration and ammoniac nitrogen concentration, pH ruminal, liquid passage, turnover and ruminal volume, and number and specie of ciliates protozoa. The experimental period was subdivided in twenty and one days of adaptation and seven of harvest, having totalized twenty and eight days for experimental period. The coefficients of degradability in the incubation periods of 0, 3, 6, 12, 24, 48, 72 and 96 hours had been measure. For the harvest of I eliminate ruminal had been used schedules 0, 2, 4, 6, 8 hours; the harvests of phase marker eliminate (PEG) had been carried through ace 0; 1,5; 3; 6; 12 and 24 hours after the feeding. It had increase of the value for fraction "b" in the MS, the treatment yeast culture, and the salinomycin treatment (p<0,05). Also it had a trend to increase fraction "b" in the FDN. The treatment yeast culture significantly increased the number of ciliates protozoa in rumen (p<0,05). The referring values to pH had not been affected by the treatments (p>0,05). The ammonia concentration and the values found for the kinetic ruminal had not been affected by the treatments (p>0,05). The use of ionophores improved the acid ratio of the acetic:propionic, propionic and butiric while the yeast culture increased the acids concentration of acetic (p<0,05).

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-05-03T17:52:07Z No. of bitstreams: 1 anacarolinarochalamego.pdf: 2896439 bytes, checksum: edd3041b783f9b2209c26f264c38080f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-06-07T15:19:22Z (GMT) No. of bitstreams: 1 anacarolinarochalamego.pdf: 2896439 bytes, checksum: edd3041b783f9b2209c26f264c38080f (MD5) / Made available in DSpace on 2016-06-07T15:19:22Z (GMT). No. of bitstreams: 1 anacarolinarochalamego.pdf: 2896439 bytes, checksum: edd3041b783f9b2209c26f264c38080f (MD5) Previous issue date: 2015-03-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A realização do inquérito malacológico de uma região é importante, pois auxilia o desenvolvimento de pesquisas de caráter mais aplicado; fornece material para estudos taxonômicos como a identificação morfológica e identidade específica; material para coleções científicas e museus; informa a riqueza de espécies – nativas, exóticas e novos registros; monitora a dispersão das espécies que atuam na transmissão de parasitos; entre outros. Além disso, fornece informações sobre a ecologia das espécies como, por exemplo, a interação com o meio ambiente e outros organismos. Interações epibióticas entre moluscos e ciliados vêm sendo registrado em diversos estudos, principalmente na Europa. Entretanto, a maior parte destes estudos relata a epibiose no ambiente marinho e não abordam aspectos ecológicos da associação entre o basibionte e epibionte. A epibiose geralmente tem caráter generalista, mas algumas espécies de epibionte podem colonizar especificamente uma ou poucas espécies de basibiontes. Os sítios de localização na superfície do basibionte também são selecionados de acordo com as necessidades ecológicas do epibionte, além de serem determinadas pelas características da biologia, fisiologia, comportamento e ecologia do basibionte, e também por fatores ambientais. Além disso, estudos vêm mostrando que as conchas dos moluscos são microhábitats favoráveis à colonização e excelente estratégia de sobrevivência. O presente estudo teve como objetivos realizar um levantamento dos moluscos límnicos, analisar a composição e estrutura da comunidade de ciliados, e investigar a distribuição espacial dos ciliados nas conchas dos moluscos ancilídeos na microrregião de Juiz de Fora. As espécies de moluscos encontradas foram Biomphalaria intermedia, Biomphalaria peregrina, Biomphalaria straminea, Biomphalaria tenagophila, Drepanotrema cimex, Gundlachia cf. lutzi, Physa acuta, Physa marmorata, Pomacea sp. e Pseudosuccinea columella. Já os ciliados associados às conchas dos moluscos foram Carchesium polypinum, Epistylis plicatilis, Epistylis chrysemydis, Epistylis sp. 1, Epistylis sp. 2, Opercularia articulata, Opercularia nutans, Opercularia sp. 1, Opercularia sp. 2, Vorticella campanula, Vorticella convallaria, Vorticella sp. 1, Vorticella sp. 2, Vorticella sp. 3, Thuricola sp., Platycola cf. decumbens, Tokophrya quadripartita, Tokophrya cf. lenarum e Stentor sp. A diversidade de ciliados e moluscos límnicos encontrados no presente estudo e o registro de epibiose entre estes organismos mostra a necessidade de ampliar os estudos abordando aspectos ecológicos, visto que é o primeiro estudo e registro de ciliados epibiontes na família Ancylidae na região Neotropical e nas espécies G. cf. lutzi, P. marmorata, P. columella e B. peregrina. Além disso, o encontro das espécies G. cf. lutzi, D. cimex, B. intermedia para o município de Juiz de Fora, B. tenagophila no município de Chácara e B. peregrina nos municípios de Lima Duarte e Belmiro Braga constituem novos registros de ocorrência. Os resultados apresentados no presente estudo confirmam a importância da realização de levantamentos dos moluscos e a importância de abordar aspectos ecológicos da associação epibiótica entre moluscos e ciliados, visto que são escassos os estudos da relação epibiótica nos ambientes de água doce. / Checklist studies on the malacofauna are of great interest since it is the first step to the development of more applied research; provides material for taxonomic studies; information on species richness - native, exotic and new records as well as on the distribution of species that act in parasites transmission. It also provides information on the ecology of the species, for example, the influence of environmental parameters and interaction with other organisms. Epibiotic interactions between molluscs and ciliates have been reported mainly in Europe. However, most of these studies report the epibiose the marine environment and do not address ecological aspects of the association between the basibionts and the epibionts. The epibiose usually has a generalist character, but some epibiont species can colonize specifically one or a few species of basibiontes. The attachment sites on the basibiont are also selected according to the epibiont ecological requirements, and are influenced by biological, physiology and behavioral features of the basibiont, but also by physical factors. In addition, studies have shown that the shells of molluscs are favorable microhabitats to colonization. This study aimed to survey limnic molluscs, analyze the composition and structure of ciliates community, and investigate the spatial distribution of ciliates in the shells of ancilid molluscs in Juiz de Fora microregion. This study reported ten species of freshwater snails: Biomphalaria intermedia, Biomphalaria peregrina, Biomphalaria straminea, Biomphalaria tenagophila, Drepanotrema cimex, Gundlachia cf. lutzi, Physa acuta, Physa marmorata, Pomacea sp. and Pseudosuccinea columella. We also found 19 species of ciliates associated to the molluscs` shells: Carchesium polypinum, Epistylis plicatilis, Epistylis chrysemydis, Epistylis sp. 1, Epistylis sp. 2, Opercularia articulata, Opercularia nutans, Opercularia sp. 1 Opercularia sp. 2, Vorticella campanula, Vorticella convallaria, Vorticella sp. 1 Vorticella sp. 2 Vorticella sp. 3 Thuricolla sp. Platycola cf. decumbens, Tokophrya cf. lenarum, Tokophrya quadripartita, and Stentor sp. Our results show the need to expand the studies on malacofauna as well as the association between snails and epibionts, since it is the first record of epibiosis by ciliates on ancylid snails in the Neotropics and the first record of epibiosis for the species G. cf. lutzi, P. marmorata, P. columella and B. peregrina. In addition, we register for the first time the occurrence of G. cf. lutzi, D. cimex, B. intermedia for the municipality of Juiz de Fora, B. tenagophila for the municipality of Chácara and B. peregrina for the municipalities of Lima Duarte and Belmiro Braga. Our results confirm the importance of holding molluscs surveys and the importance of addressing epibiotic association between molluscs and ciliates, since there are few studies concerning this ecological relationship.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-06-12T11:58:26Z No. of bitstreams: 0 / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-06-14T12:44:23Z (GMT) No. of bitstreams: 0 / Made available in DSpace on 2018-06-14T12:44:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-26 / A família Cycloposthiidae (Ciliophora, Trichostomatia) inclui protozoários ciliados simbiontes intestinais de mamíferos herbívoros conhecidos por contribuir de forma significativa no metabolismo digestivo de seus hospedeiros. Atualmente, é representada por 69 espécies, divididas em 17 gêneros. Entretanto, devido à ausência de padrão metodológico para descrições de espécies, bem como diversas outras incongruências taxonômicas, a sistemática da família Cycloposthiidae necessita de ampla reformulação. Estudos recentes tem demonstrado que a família Cycloposthiidae não é monofilética, porém, há escassez de dados molecures para investigar tais relações. Esta dissertação encontra-se dividida em duas seções. A Seção 1 apresenta breve revisão taxonômica da família Cycloposthiidae, com dados sobre taxonomia, morfologia, checklist de espécies, hospedeiros e distribuição geográfica, e discute a validade dos táxons pertencentes à família, a fim de refletir sobre a sistemática do grupo. A Seção 2 apresenta dados sobre filogenia molecular de representantes da família Cycloposthiidae e fornece dez novas sequências, sendo nove de representantes do gênero Cycloposthium e uma do gênero Monoposthium, a fim de investigar a relação entre os membros da família Cycloposthiidae e demais ciliados tricostomatídeos, e investigar a evolução de alguns caracteres morfológicos dentro do gênero Cycloposthium. Deste modo, ressalta-se a importância de conhecer melhor os representantes da família Cycloposthiidae, a considerar sua diversidade, amplo espectro de hospedeiros nos quais estas espécies ocorrem e sua importância na digestão desses animais. / The family Cycloposthiidae (Ciliophora, Trichostomatia) includes symbiotic intestinal ciliates of herbivorous mammals known to contribute significantly to the digestive metabolism of their hosts. Currently, it is represented by 69 species, divided into 17 genera. However, because to the absence of a methodological pattern for species descriptions, as well as several other taxonomic incongruities, the systematics of the family Cycloposthiidae requires extensive reformulation. Recent studies have shown that the family Cycloposthiidae is not monophyletic, however, there is a paucity of molecular data to investigate such relationships. This dissertation is divided into two sections. Section 1 presents a brief taxonomic review of the family Cycloposthiidae, with data on taxonomy, morphology, species checklists, hosts and geographic distribution, and discusses the validity of taxa belonging to the family, with the objective to reflect on the group's systematics. Section 2 presents data on molecular phylogeny of representatives of the family Cycloposthiidae and provides ten new sequences, nine of which are representatives of the genus Cycloposthium and one of the genus Monoposthium, with the objective to investigate the relationships between the members of the family Cycloposthiidae and other tricostomatids ciliates, and to investigate the evolution of some characters within the genus Cycloposthium. In this way, it is emphasized the importance of knowing better the family Cycloposthiidae, to consider its diversity, wide spectrum of hosts where the family occurs and its importance in the digestion of these animals.

La publication du génome de la paramécie (Aury, 2006) a révélé une séquence atypique particulièrement intéressante pour les études de génomique évolutive. Au cours de cette thèse, j’ai mené une analyse bioinformatique détaillée de ce génome en me concentrant particulièrement sur les trois points suivants : 1) Le rôle de deux classes distinctes de petits ARN fonctionnels non codants, l’une intervenant dans les processus de régulation de l’expression des gènes tandis que l’autre participe aux réarrangements génomiques (élimination de fragments d’ADN) associés au cycle sexuel de la paramécie. 2) L’évolution des paires de gènes après une duplication globale de génome (WGD). En effet, avec une WGD relativement récente précédée de deux autres WGDs plus anciennes encore bien visibles, la paramécie est un modèle de choix pour cette étude. Nous avons pu montrer que la rétention des deux copies d’un gène après une WGD est fortement corrélée au niveau d’expression des gènes. Nous proposons un modèle basé sur les coûts et bénéfices de l’expression des gènes pour expliquer cette observation. 3) L’analyse de contraintes sélectives sur les introns pour produire des messagers détectables par le Nonsense-Mediated mRNA Decay (NMD). Ces contraintes sélectives, mises en évidence initialement chez la paramécie, se sont avérées être présentes chez tous les eucaryotes que nous avons pu analyser, ce qui nous amène à questionner l’efficacité des mécanismes d’épissage chez les eucaryotes et le rôle du NMD dans la prévention des erreurs d’épissage. L’ensemble de ces analyses a permis de mieux comprendre un certain nombre de mécanismes évolutifs universels / This work presents a detailed analysis of the paramecium genome, with focusing more precisely on the 3 following topics : 1) The role of two distinct classes of small non-coding RNAs. The first one (siRNAs) being involved in post-transcriptional gene silencing while the other (scanRNAs) plays a crucial role during the massive genomic rearrangements that occur in ciliates after sexual reproduction (Lepère et al. 2009). 2) The evolution of duplicated genes following Whole-Genome Duplications (WGDs). Indeed, the paramecium genome contains evidences for 3 successive WGDs (Aury et al. 2006), which explains why this organisms is perfectly well suited for such an analysis. We show that retention of duplicated genes is strongly correlated to their expression level and we propose a model based on cost and benefit of gene expression to explain this pattern. 3) The analysis of the extremely tiny introns in paramecium (99% of introns are less than 20-33nt in length) revealed the presence of a translational control of splicing in eukaryotes. This work suggests that splicing errors are frequent and that eukaryotic cells rely on the Nonsense-mediated mRNA Decay to detect aberrant transcripts produced by splicing errors (Jaillon et al. 2008). These analyses provide new insights on several evolutionary mechanisms that shape the genomes of eukaryotes

Ciliates are the most diversified protists in suboxic and anoxic habitats where they often form symbioses with prokaryotes. Although the diversity of anaerobic ciliates has been overlooked for a long time, anaerobic representatives can be found in most ciliate classes. This study focuses on anaerobic ciliates from the subclass Scuticociliatia, a neglected lineage, which belongs to the species-rich class Oligohymenophorea. One of the main outcomes resulting from this study is the discovery of a novel anaerobic clade of ciliates, from which only one species has been described molecularly to date. We have shown that the clade represents a diversified lineage, likely a new order. Thanks to the sampling of many freshwater and marine anoxic sediments, we have established the largest culture collection of anaerobic scuticociliates in the world. This has enabled us to determine the 18S rRNA gene sequences of 55 cultured anaerobic scuticociliates and to study their morphology both in-vivo and using various silver- impregnation methods. Besides, we applied transmission and scanning electron microscopy techniques to study the ultrastructure of both ciliates and symbionts. To identify the symbionts, we also employed other methods including microbiome sequencing and fluorescence in-situ hybridization. Since all...

No description available.

Comme tous les ciliés, P. tetraurelia réarrange son génome à chaque génération sexuelle pendant le développement de son macronoyau somatique ¿ partir du micronoyau germinal. Les réarrangements incluent l’excision précise de courtes séquences dérivant de transposons et appelés IES (Internal Eliminated Sequences) dont la majorité sont intragéniques. L’excision d’une fraction d’entre elles dépend de petits ARN maternels (appelés scnARN) qui sont produits à partir de tout le génome germinal pendant la méiose. Ce mécanisme pose un problème lors d’une conjugaison entre deux souches présentant des polymorphismes d’insertion : une cellule sera théoriquement incapable d’exciser une IES portée par l’allèle paternel reçu si cette IES est absente de l’allèle maternel ou si la séquence est trop divergente. Mes résultats montrent cependant que les allèles paternels divergents sont correctement excisés en utilisant les scnARN produit par la cellule paternelle. Dans le cas d’un polymorphisme absence/présence, l’IES que j’ai étudié est excisée chez 70 % des hétérozygotes F1, également via les scnARN paternels. Nous avons exploré deux hypothèses pour expliquer comment ils pouvaient agir. Il pourrait s’agir d’une programmation précoce des noyaux gamétiques ou alors d’un échange cytoplasmique des scnARN. Finalement, j’ai montré qu’un défaut de scnARN maternels n’est pas une cause possible de dysgénésie hybride. Cependant, 30 % des hétérozygotes F1 présentent une rétention variable de l’IES étudié via un mécanisme inconnu. Si cela est généralisable à toutes les IES homozygotes, alors ce mécanisme aurait un effet délétère sérieux sur les F1 et pourrait contribuer à l’isolement reproductif. / Like all ciliates, P. tetraurelia entirely rearranges its genome during development of the somatic macronucleus from the germline micronucleus, in each sexual generation. Rearrangements include the precise excision of IESs (Internal Eliminated Sequences), single-copy intervening sequences likely derived from transposon insertions. At least for a fraction of IESs, correct excision, which is required to reconstitute functional genes in the macronucleus, is thought to depend on their recognition by Piwi-bound small RNAs (called scnRNAs) produced from the maternal germline genome during meiosis. This raises a problem during conjugation between strains presenting insertion polymorphisms: a cell will be theoretically unable to excise an IES from the incoming (paternal) allele if that IES is absent from the maternal allele, or if its sequence is too divergent. Our results, however, indicate that divergent paternal alleles are correctly rearranged, using scnRNAs produced by the paternal cell. In the case of an absence/presence polymorphism, the IES we studied is excised in 70% of heterozygotes, also using paternal scnRNAs. We explored two hypotheses to explain how they can act. It could be either an early programming of the gametic nuclei or through cytoplasmic exchange of scnRNAs. My results seem to favor the latter. Overall, I showed that the lack of maternal scnRNAs is not a possible cause of hybrid dysgenesis. However, 30% of heterozygous F1 display a variable retention of the IES through an unknown mechanism. If this is true for all hemizygous IESs then it will have a strong deleterious effect on hybrid F1s and may contribute to reproductive isolation.

<p>Temporal and spatial variations of pelagic microorganisms in the northern Baltic Sea were studied, as well as factors influencing their abundance and growth rates. Three main questions were asked 1) How does increased productivity influence the structure of the microbial food web? 2) Does predation limitation vary between trophic levels? 3) What is the relative importance of resource and predation limitation at different trophic levels?</p><p>A field study in the northern Baltic Sea showed that dominating protozoa, flagellates and ciliates, increased with increasing primary productivity from north to south. Furthermore, relatively small protozoan cells dominated in the low productive north, while larger cells became more dominant in the south. The relationship between plankton size structure and productivity was further studied in an experimental system. In agreement with present theories regarding nutrient status of pelagic food webs, increased productivity caused a lengthening of the food chain as well as a change in plankton size structure. While microplankton dominated in nutrient rich treatments pico- and nanoplankton dominated during nutrient poor treament. The flagellate community was dominated by a potentially mixotroph, <i>Chrysochromulina</i> sp., at low nutrient concentrations. To our knowledge this is the first experimental study showing that <i>Chrysochromulina</i> sp. in resemblance with other mixotrophs is favoured by nutrient poor conditions compared to strict autotrophs and heterotrophs.</p><p>During a stratified summer period autotrophic microorganisms in the northern Baltic Sea did not respond to removal of potential predators, indicating that they were primarily limited by inorganic nutrients. An exception was small eucaryotic picoplankton that showed a large response to predator removal. Among the heterotrophic microorganisms direct effect of predation seemed to increase from ciliates, heterotrophic bacteria, small heterotrophic flagellates, medium flagellates to large flagellates. No quick indirect effect was observed, but after four days trophic cascades were detected.</p><p>The relative importance of resource and predation limitation was studied among heterotrophic bacteria, flagellates and ciliates in the northern Baltic Sea. For all these groups, resource limitation seemed to prevail during the summer period. The results also indicated that the relative importance of predation increased with the productivity of the system. To our knowledge there are no earlier measurements on the relative importance of resource and predation limitation for micoorganisms in the pelagic environment.</p>