| 1. |
- Airaud, M, et al.
(författare)
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Biologie - Les manuels visuels pour la Licence
- 2018
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- En couleurs et très illustré, ce manuel a été conçu pour vous qui débutez un cursus scientifique universitaire. Il vous permettra d’acquérir les connaissances fondamentales en biologie, mais aussi la démarche et la rigueur scientifiques indispensables aux études supérieures. De multiples rubriques vous garantissent un apprentissage progressif et complet : un cours visuel avec de nombreux exemples concrets pour introduire et illustrer les notions et concepts clés ; des encadrés méthodologiques pour vous guider vers les bonnes pratiques et vous faire découvrir les grandes méthodes expérimentales ; des focus sur des applications, sujets de recherche ou thèmes d’actualité ; des repères historiques ; de nombreux QCM et exercices (tous corrigés) pour tester vos acquis et vous entraîner.
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| 2. |
- Caputo, Andrea, 1988-
(författare)
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Genomic and morphological diversity of marine planktonic diatom-diazotroph associations : a continuum of integration and diversification through geological time
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Symbioses between eukaryotes and nitrogen (N2)-fixing cyanobacteria (or diazotrophs) are quite common in the plankton community. A few genera of diatoms (Bacillariophyceae) such as Rhizosolenia, Hemiaulus and Chaetoceros are well known to form symbioses with the heterocystous diazotrophic cyanobacteria Richelia intracellularis and Calothrix rhizosoleniae. The latter are also called diatom-diazotroph associations, or DDAs. Up to now, the prokaryotic partners have been morphologically and genetically characterized, and the phylogenetic reconstruction of the well conserved nifH gene (encodes for the nitrogenase enzyme) placed the symbionts in 3 clusters based on their host-specificity, i.e. het-1 (Rhizosolenia-R. intracellularis), het-2 (Hemiaulus-R. intracellularis), and het-3 (Chaetoceros-C- rhizosoleniae). Conversely, the diatom-hosts, major representative of the phytoplankton community and crucial contributors to the carbon (C) biogeochemical cycle, have been understudied.The first aim of this thesis was to genetically and morphologically characterize the diatom-hosts, and to reconstruct the evolutionary background of the partnerships and the symbiont integration in the host. The molecular-clock analysis reconstruction showed the ancient appearance of the DDAs, and the traits characterizing the ancestors. In addition, diatom-hosts bearing internal symbionts (with more eroded draft genomes) appeared earlier than diatom-hosts with external symbionts. Finally a blast survey highlighted a broader distribution of the DDAs than expected.The second aim of this thesis was to compare genetic and physiological characteristics of the DDAs symbionts with the other eukaryote-diazotroph symbiosis, i.e. prymnesiophyte-UCYN-A (or Candidatus Atelocyanobacterium thalassa). The genome comparison highlighted more genes for transporters in het-3 (external symbiont) and in the UCYN-A based symbiosis, suggesting that symbiont location might be relevant also for metabolic exchanges and interactions with the host and/or environment. Moreover, a summary of methodological biases that brought to an underestimation of the DDAs is reported.The third aim of this thesis was to determine the distribution of the DDAs in the South Pacific Ocean using a quantitative polymerase chain reaction (qPCR) approach and to outline the environmental drivers of such distribution. Among the het-groups, het-1 was the most abundant/detected and co-occurred with the other 2 symbiotic strains, all responding similarly to the influence of abiotic factors, such as temperature and salinity (positive and negative correlation, respectively). Globally, Trichodesmium dominated the qPCR detections, followed by UCYN-B. UCYN-A phylotypes (A-1, A-2) were detected without their proposed hosts, for which new oligonucleotides were designed. The latter suggested a facultative symbiosis. Finally, microscopy observations of the het-groups highlighted a discrepancy with the qPCR counts (i.e. the former were several order of magnitudes lower), leading to the idea of developing a new approach to quantify the DDAs. The fourth aim of this thesis was to develop highly specific in situ hybridization assays (CARD-FISH) to determine the presence of alternative life-stages and/or free-living partners. The new assays were applied to samples collected in the South China Sea and compared with abundance estimates from qPCR assays for the 3 symbiotic strains. Free-living cells were indeed detected along the transect, mainly at deeper depths. Free-living symbionts had two morphotypes: trichomes and single-cells. The latter were interpreted as temporary life-stages. Consistent co-occurrence of the 3 het-groups was also found in the SCS and application of a SEM model predicted positive interactions between the het groups. We interpreted the positive interaction as absence of intra-specific competition, and consistent with the previous study, temperature and salinity were predicted as major drivers of the DDAs distribution.
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| 3. |
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| 5. |
- Tedersoo, Leho, et al.
(författare)
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Response to Comment on “Global diversity and geography of soil fungi”
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 349:6251
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Schadt and Rosling (Technical Comment, 26 June 2015, p. 1438) argue that primer-template mismatches neglected the fungal class Archaeorhizomycetes in a global soil survey. Amplicon-based metabarcoding of nine barcode-primer pair combinations and polymerase chain reaction (PCR)–free shotgun metagenomics revealed that barcode and primer choice and PCR bias drive the diversity and composition of microorganisms in general, but the Archaeorhizomycetes were little affected in the global study. We urge that careful choice of DNA markers and primers is essential for ecological studies using high-throughput sequencing for identification.
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| 6. |
- Janzon, Anders, 1978, et al.
(författare)
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Exploring the microbial resistome in river sediments exposed to extraordinary high levels of antibiotics
- 2010
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Ingår i: 35th FEBS Congress: Molecules of Life.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The rapid development and propagation of antibiotic resistance in pathogenic and opportunistic bacteria is a major threat to public health worldwide. The phenomenon has been widely studied in the clinical setting, but comparatively little is known about the prevalence and diversity of antibiotic resistance in communities of environmental bacteria, often referred to as the environmental resistome. As the external environment may function as a reservoir of resistance genes to human pathogens, we are interested in how environmental bacteria are affected by antibiotic pollution. We have previously isolated microbial DNA from river sediments taken up- and downstream from a water treatment plant that processes waste water from several pharmaceutical plants producing antibiotics. In a previous study, we used deep sequencing to identify unprecedented frequencies of known resistance genes to several classes of antibiotics in these samples. In this study, we aim to functionally characterize the resistome in a more open and exploratory way by screening genomic DNA libraries transformed into sensitive hosts. To generate the libraries, several experimental strategies were explored, including mechanical shearing and enzymatic digestion of the isolated DNA followed by blunt- or sticky end cloning into different plasmids, subsequently transformed into sensitive E. coli. Pros and cons of the different strategies will be discussed along with preliminary results of the screening against selected antibiotics.
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| 8. |
- Sandström, Olof, et al.
(författare)
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Miljöpåverkan av skogsindustriutsläpp
- 1997
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Ingår i: Naturvårdsverkets rapportserie. Rapport 4695. ; , s. 1-89
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
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| 10. |
- Kvarnemo, Charlotta, 1963, et al.
(författare)
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Gravida hanar och konkurrerande honor
- 2014
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Ingår i: Havsutsikt. - 1104-0513. ; 2014:1, s. 6-7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Hos fisken tångsnälla blir pappan gravid. Hanen förser ungarna med syre och näring under utvecklingen, men han kan också själv ta upp näring som kommer från äggen. Honor konkurrerar om att få para sig med hanar som har plats för hennes ägg, och de gillar särskilt att para sig med stora hanar. Trots det ger de ägg med mer näring till små hanar.
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