Learning ability and longevity: a symmetrical evolutionary trade-off in Drosophila.

Learning ability can be substantially improved by artificial selection in animals ranging from Drosophila to rats. Thus these species have not used their evolutionary potential with respect to learning ability, despite intuitively expected and experimentally demonstrated adaptive advantages of learning. This suggests that learning is costly, but this notion has rarely been tested. Here we report correlated responses of life-history traits to selection for improved learning in Drosophila melanogaster. Replicate populations selected for improved learning lived on average 15% shorter than the corresponding unselected control populations. They also showed a minor reduction in fecundity late in life and possibly a minor increase in dry adult mass. Selection for improved learning had no effect on egg-to-adult viability, development rate, or desiccation resistance. Because shortened longevity was the strongest correlated response to selection for improved learning, we also measured learning ability in another set of replicate populations that had been selected for extended longevity. In a classical olfactory conditioning assay, these long-lived flies showed an almost 40% reduction in learning ability early in life. This effect disappeared with age. Our results suggest a symmetrical evolutionary trade-off between learning ability and longevity in Drosophila.

Morphometric shape analysis using learning vector quantization neural networks - an example distinguishing two microtine vole species

Closely related species may be very difficult to distinguish morphologically, yet sometimes morphology is the only reasonable possibility for taxonomic classification. Here we present learning-vector-quantization artificial neural networks as a powerful tool to classify specimens on the basis of geometric morphometric shape measurements. As an example, we trained a neural network to distinguish between field and root voles from Procrustes transformed landmark coordinates on the dorsal side of the skull, which is so similar in these two species that the human eye cannot make this distinction. Properly trained neural networks misclassified only 3% of specimens. Therefore, we conclude that the capacity of learning vector quantization neural networks to analyse spatial coordinates is a powerful tool among the range of pattern recognition procedures that is available to employ the information content of geometric morphometrics.

Estudo de caso: o uso da língua portuguesa por jovens provindos de outros países no domínio privado, público e educativo

A afluência de imigrantes a Portugal, nas últimas três décadas transformou radicalmente todo o tecido social português, caracterizando-se hoje pela sua heterogeneidade. Até ao início da década de 90 do século XX, os fluxos migratórios provinham essencialmente dos Países de Língua Oficial Portuguesa, com maior incidência de Cabo Verde, Brasil e Angola. É nessa década que se registam movimentos bastante significativos de imigrantes provenientes da Europa Central e Oriental, principalmente da Ucrânia, Rússia, Roménia e Moldávia, assim como da Ásia, destacando-se os naturais da China, Índia, Paquistão e das antigas repúblicas soviéticas. De acordo com a análise apresentada pelo Instituto Nacional de Estatística em Dezembro de 2006, residiam de forma legal em Portugal 329 898 cidadãos de nacionalidade estrangeira, sendo as maiores comunidades de Cabo Verde (57 349), Brasil (41 728) e Angola (28 854). A sociedade portuguesa do século XXI, distancia-se cada vez mais do conceito de monolinguismo, tal como se evidencia no Projecto Gulbenkian “Diversidade Linguística na Escola Portuguesa”, que, segundo o estudo feito, onze por cento dos alunos residentes na área da Grande Lisboa nasceram fora de Portugal e têm como línguas maternas cinquenta e oito idiomas. É urgente uma intervenção diferente no que corresponde a esta nova realidade linguística em Portugal e sobretudo no que concerne à integração do “outro”, reconhecendo e respeitando as várias línguas maternas e culturas, como também a sua preservação a fim de possibilitar o desenvolvimento íntegro e harmonioso da identidade. A heterogeneidade da actual sociedade portuguesa impõe um olhar atento para com esta nova realidade no país, sobretudo em muitas das escolas onde a par do uso da língua portuguesa outras línguas são também usadas como forma de comunicação entre os mesmos pares, situação esta perfeitamente desajustada da realidade escolar madeirense Estudo de caso: O uso da Língua Portuguesa por jovens oriundos de outros países nos domínios privado, público e educativo. 10 de inícios da década de 90 do século XX, à excepção dos alunos provenientes da Venezuela, os denominados luso-descendentes. A escola mudara, tudo se alterara, havia que tentar perceber o que estava a ocorrer, um novo Mundo “invadira” as turmas, prontas a aprender, a saber, a descobrir. Era preciso preencher o silêncio expectante. Aprender uma nova língua, a portuguesa, decorrente da obrigatoriedade implícita de tratar-se da língua oficial, obrigava a repensar o ensino, a continuamente desvendar novos caminhos possibilitadores de encontro entre a língua materna e a segunda, de reencontro com a identidade linguística e cultural que não se quer perdidas, só tornado possível na diferença. A par de uma escola que se apresentava de forma diferente, cuja intervenção teria de ser oposta à de então, uma vez que a aprendizagem do português era feita como língua segunda (L2), muitas foram e são as inquietações, um turbilhão de interrogações decorriam deste contacto constante de uma língua que se diz minha, fonte de partilha com outros jovens. O uso da língua portuguesa confinar-se-á unicamente à escola com os professores e colegas ou despoletará curiosidades, vontades, interesses, motivados por objectivos confinados ao percurso e à história humana? Muitas são as interrogações que ocorrem, muitos são também os momentos de sabedoria mútua de línguas e países a desvendar num contínuo ininterrupto e é essa constante procura que determina a busca de respostas. Entre muitas interrogações uma afigurava-se de forma latente, quiçá fonte de resposta para outras interrogações inerentes à língua portuguesa como língua segunda. A sua utilização por parte dos alunos de outras nacionalidades nos domínios privado, público e educativo engloba domínios diversos capazes de informar acerca do uso dessa mesma língua. Importa no entanto reforçar que estes alunos constituem um grupo heterogéneo sob diversos pontos de vista: etário, linguístico e cultural. Do ponto de vista linguístico a população que tem o português como língua segunda abrange alunos falantes de diferentes línguas maternas, umas mais próximas, outras mais afastadas do português, propiciando diferentes graus de transferência de conhecimentos linguísticos e de experiências comunicativas, como também em diferentes estádios de aquisição e que fora da escola o usam em maior ou menor número de contextos e com um grau de frequência desigual. Estudo de caso: O uso da Língua Portuguesa por jovens oriundos de outros países nos domínios privado, público e educativo. 11 Dispõem também de diferentes capacidades individuais para discriminar, segmentar e produzir sequências linguísticas. Já do ponto de vista cultural apresentam diferentes hábitos de aprendizagem, bem como diferentes representações e expectativas face à escola. Todos estes factores determinarão ritmos de progressão distintos no que respeita à aprendizagem do português como língua segunda. As oportunidades de aprendizagem e de uso que cada indivíduo tem ao longo da vida, determinantes no processo de aquisição, desenvolvimento e aprendizagem de uma língua, variam bastante de indivíduo para indivíduo. Os alunos podem viver num mesmo contexto no entanto razões variadíssimas determinarão diferentes oportunidades de aprendizagem e de uso. Viver-se num contexto de imersão não é suficiente para que todos tenham o mesmo grau de exposição a material linguístico rico e variado da L2. Essas oportunidades também se relacionam com a distância linguística entre língua primeira (L1) e a língua segunda, quanto mais afastadas são as duas línguas mais os falantes da L2 se refugiam na sua língua materna, assim como também se associam aos hábitos culturais da comunidade e da família.

Estudo de caso : o uso da língua portuguesa por jovens provindos de outros países no domínio privado, público e educativo

A afluência de imigrantes a Portugal, nas últimas três décadas transformou radicalmente todo o tecido social português, caracterizando-se hoje pela sua heterogeneidade. Até ao início da década de 90 do século XX, os fluxos migratórios provinham essencialmente dos Países de Língua Oficial Portuguesa, com maior incidência de Cabo Verde, Brasil e Angola. É nessa década que se registam movimentos bastante significativos de imigrantes provenientes da Europa Central e Oriental, principalmente da Ucrânia, Rússia, Roménia e Moldávia, assim como da Ásia, destacando-se os naturais da China, Índia, Paquistão e das antigas repúblicas soviéticas. De acordo com a análise apresentada pelo Instituto Nacional de Estatística em Dezembro de 2006, residiam de forma legal em Portugal 329 898 cidadãos de nacionalidade estrangeira, sendo as maiores comunidades de Cabo Verde (57 349), Brasil (41 728) e Angola (28 854). A sociedade portuguesa do século XXI, distancia-se cada vez mais do conceito de monolinguismo, tal como se evidencia no Projecto Gulbenkian “Diversidade Linguística na Escola Portuguesa”, que, segundo o estudo feito, onze por cento dos alunos residentes na área da Grande Lisboa nasceram fora de Portugal e têm como línguas maternas cinquenta e oito idiomas. É urgente uma intervenção diferente no que corresponde a esta nova realidade linguística em Portugal e sobretudo no que concerne à integração do “outro”, reconhecendo e respeitando as várias línguas maternas e culturas, como também a sua preservação a fim de possibilitar o desenvolvimento íntegro e harmonioso da identidade. A heterogeneidade da actual sociedade portuguesa impõe um olhar atento para com esta nova realidade no país, sobretudo em muitas das escolas onde a par do uso da língua portuguesa outras línguas são também usadas como forma de comunicação entre os mesmos pares, situação esta perfeitamente desajustada da realidade escolar madeirense Estudo de caso: O uso da Língua Portuguesa por jovens oriundos de outros países nos domínios privado, público e educativo. 10 de inícios da década de 90 do século XX, à excepção dos alunos provenientes da Venezuela, os denominados luso-descendentes. A escola mudara, tudo se alterara, havia que tentar perceber o que estava a ocorrer, um novo Mundo “invadira” as turmas, prontas a aprender, a saber, a descobrir. Era preciso preencher o silêncio expectante. Aprender uma nova língua, a portuguesa, decorrente da obrigatoriedade implícita de tratar-se da língua oficial, obrigava a repensar o ensino, a continuamente desvendar novos caminhos possibilitadores de encontro entre a língua materna e a segunda, de reencontro com a identidade linguística e cultural que não se quer perdidas, só tornado possível na diferença. A par de uma escola que se apresentava de forma diferente, cuja intervenção teria de ser oposta à de então, uma vez que a aprendizagem do português era feita como língua segunda (L2), muitas foram e são as inquietações, um turbilhão de interrogações decorriam deste contacto constante de uma língua que se diz minha, fonte de partilha com outros jovens. O uso da língua portuguesa confinar-se-á unicamente à escola com os professores e colegas ou despoletará curiosidades, vontades, interesses, motivados por objectivos confinados ao percurso e à história humana? Muitas são as interrogações que ocorrem, muitos são também os momentos de sabedoria mútua de línguas e países a desvendar num contínuo ininterrupto e é essa constante procura que determina a busca de respostas. Entre muitas interrogações uma afigurava-se de forma latente, quiçá fonte de resposta para outras interrogações inerentes à língua portuguesa como língua segunda. A sua utilização por parte dos alunos de outras nacionalidades nos domínios privado, público e educativo engloba domínios diversos capazes de informar acerca do uso dessa mesma língua. Importa no entanto reforçar que estes alunos constituem um grupo heterogéneo sob diversos pontos de vista: etário, linguístico e cultural. Do ponto de vista linguístico a população que tem o português como língua segunda abrange alunos falantes de diferentes línguas maternas, umas mais próximas, outras mais afastadas do português, propiciando diferentes graus de transferência de conhecimentos linguísticos e de experiências comunicativas, como também em diferentes estádios de aquisição e que fora da escola o usam em maior ou menor número de contextos e com um grau de frequência desigual. Estudo de caso: O uso da Língua Portuguesa por jovens oriundos de outros países nos domínios privado, público e educativo. 11 Dispõem também de diferentes capacidades individuais para discriminar, segmentar e produzir sequências linguísticas. Já do ponto de vista cultural apresentam diferentes hábitos de aprendizagem, bem como diferentes representações e expectativas face à escola. Todos estes factores determinarão ritmos de progressão distintos no que respeita à aprendizagem do português como língua segunda. As oportunidades de aprendizagem e de uso que cada indivíduo tem ao longo da vida, determinantes no processo de aquisição, desenvolvimento e aprendizagem de uma língua, variam bastante de indivíduo para indivíduo. Os alunos podem viver num mesmo contexto no entanto razões variadíssimas determinarão diferentes oportunidades de aprendizagem e de uso. Viver-se num contexto de imersão não é suficiente para que todos tenham o mesmo grau de exposição a material linguístico rico e variado da L2. Essas oportunidades também se relacionam com a distância linguística entre língua primeira (L1) e a língua segunda, quanto mais afastadas são as duas línguas mais os falantes da L2 se refugiam na sua língua materna, assim como também se associam aos hábitos culturais da comunidade e da família.

Money and prices in models of bounded rationality in high inflation economies

This paper studies the short run correlation of inflation and money growth. We study whether a model of learning can do better than a model of rational expectations, we focus our study on countries of high inflation. We take the money process as an exogenous variable, estimated from the data through a switching regime process. We findthat the rational expectations model and the model of learning both offer very good explanations for the joint behavior of money and prices.

Psychological profile of adolescents with a kidney transplant.

To describe the psychological profile of renal transplant adolescents compared to healthy peers and to adolescents with CKD, three groups of adolescents aged 12-18 yr were selected: TX, CX, and adolescents with CKD. Psychiatric symptoms and disorders were evaluated through direct interviews (K-SADS-PL) and self-report questionnaires (YSR and CBCL). Forty TX (14 LRD and 26 DD transplant recipients), 40 CX and 20 CKD were included. Twelve of 40 (30%) TX, three of 20 (15%) CKD, and three of 40 (7.5%) CX had a history of learning difficulties (p = 0.03). Compared to CX, TX had lower total YSR competencies score (p = 0.028) and lower total CBCL competencies score (p = 0.003). Twenty-six of 40 (65%) TX, 12 of 20 (60%) CKD and 15 of 40 (37.5%) CX (p = 0.038) met DSM-IV diagnostic criteria for lifetime psychiatric disorder, with rates of depressive disorder of 35% among TX and CKD compared to 15.2% among CX (p = 0.043). Eight of 40 (20%) TX had a history of simple phobia. Nine of 40 (22.5%) TX met diagnostic criteria for ADHD as compared to one of 20 (5%) CKD and three of 40 (7.5%) CX. In the TX group, we found no significant differences in educational and psychiatric variables between LRD and DD. In conclusion, we found a high prevalence of psychiatric morbidity (depression, phobia, ADHD), educational impairment and social competence problems in the TX group. CKD scored in between TX and CX on most measures.

Estimating learning models from experimental data

We study the statistical properties of three estimation methods for a model of learning that is often fitted to experimental data: quadratic deviation measures without unobserved heterogeneity, and maximum likelihood withand without unobserved heterogeneity. After discussing identification issues, we show that the estimators are consistent and provide their asymptotic distribution. Using Monte Carlo simulations, we show that ignoring unobserved heterogeneity can lead to seriously biased estimations in samples which have the typical length of actual experiments. Better small sample properties areobtained if unobserved heterogeneity is introduced. That is, rather than estimating the parameters for each individual, the individual parameters are considered random variables, and the distribution of those random variables is estimated.

Sex ratios in juveniles and adults of Dichroplus maculipennis (Blanchard) and Borellia bruneri (Rehn) (Orthoptera: Acrididae)

Dichroplus maculipennis and Borellia bruneri are two of the 18 grasshopper species of actual or potential economic relevance as pests in Argentina. The objective of this study was to estimate the sex ratios for adults and older nymphs of D. maculipennis and B. bruneri in the field, and analyze possible temporal variations. The study was conducted during seven seasons (2005-06 to 2011-12) in representative plant communities of the southern Pampas region. A total of 4536 individuals of D. maculipennis, and 6038 individuals of B. bruneri were collected. The sex ratio registered in older nymphs for D. maculipennis and B. bruneri did not deviate from a 1:1 ratio (p > 0.05), suggesting that these species have such a primary sex ratio. However, a significant bias in sex composition in adults of both species was observed (p < 0.05). The sex ratio in adults of D. maculipennis was different in five of the 18 sampling dates carried out. In three sampling dates it was biased toward males, while in the other two it was biased toward females. Taking into account the sex ratio by sampling season, significant differences were recorded in two seasons. In 2007-08 the sex ratio was biased toward males (1 F:2.26 M), while in 2008-09 it was biased toward females (1.35 F:1 M). The sex ratio in adults of B. bruneri was always biased toward males (p < 0.05). We conclude that results obtained in this study indicate that various factors like differential survival, dispersion, predation, among others, could have modified the primary sex ratio in these species.

Ecological assembly rules in plant communities--approaches, patterns and prospects.

Understanding how communities of living organisms assemble has been a central question in ecology since the early days of the discipline. Disentangling the different processes involved in community assembly is not only interesting in itself but also crucial for an understanding of how communities will behave under future environmental scenarios. The traditional concept of assembly rules reflects the notion that species do not co-occur randomly but are restricted in their co-occurrence by interspecific competition. This concept can be redefined in a more general framework where the co-occurrence of species is a product of chance, historical patterns of speciation and migration, dispersal, abiotic environmental factors, and biotic interactions, with none of these processes being mutually exclusive. Here we present a survey and meta-analyses of 59 papers that compare observed patterns in plant communities with null models simulating random patterns of species assembly. According to the type of data under study and the different methods that are applied to detect community assembly, we distinguish four main types of approach in the published literature: species co-occurrence, niche limitation, guild proportionality and limiting similarity. Results from our meta-analyses suggest that non-random co-occurrence of plant species is not a widespread phenomenon. However, whether this finding reflects the individualistic nature of plant communities or is caused by methodological shortcomings associated with the studies considered cannot be discerned from the available metadata. We advocate that more thorough surveys be conducted using a set of standardized methods to test for the existence of assembly rules in data sets spanning larger biological and geographical scales than have been considered until now. We underpin this general advice with guidelines that should be considered in future assembly rules research. This will enable us to draw more accurate and general conclusions about the non-random aspect of assembly in plant communities.

Hacia la autoformación permanente de los docentes en las comunidades de práctica: los talleres de internet en el Aula

El objetivo principal de este trabajo es determinar si las comunidades virtuales de práctica son un espacio adecuado para la autoformación de los docentes. Con este fin, primero se especifican algunos conceptos clave que ayuden a contextualizar el tema de la formación; en segundo lugar se recogen los rasgos que se consideran hoy necesarios para llevar a cabo la labor docente, dibujándose así el perfil “ideal” del profesor en el contexto actual desde distintos ángulos de vista; y por último, se narran algunas experiencias personales en las redes sociales para ilustrar el funcionamiento de este nuevo paradigma social.

Pollution stress on aquatic microbial communities

Thousands of chemical compounds enter the natural environment but many have unknown effects and consequences, in particular at low concentrations. This thesis work contributes to our understanding of pollution effects by using bacteria as test organisms. Bacteria are important for this question because some of them degrade and transform pollutants into less harmful compounds, but secondly because they themselves can be inhibited in their reproduction by exposure to toxic compounds. When inhibitory effects occur this may change the composition of the microbial com¬munity in the long run, leading to altered or diminished ecosystem services by those communities. As a result chemicals of anthropogenic origin may accumulate and per¬sist in the environment, and finally, affect higher organisms as well. In addition to acquiring basic understanding of pollutant effects at low concentrations on bacterial communities an applied goal of this thesis work was to develop bacteria-based tests to screen new organic chemicals for toxicity and biodégradation. In the first part of this work we developed a flow cytometry-based assay on SYT09 plus ethidium-bromide or propidium-iodide stained cells of Pseudomonas ûuorescens exposed or not to a variety of pollutants under oligotrophic growth conditions. Flow cytometry (FC) allows fast and accurate counting of bacterial cells under simul¬taneous assessment of their physiological state, in particular in combination with different fluorescent dyes. Here we employed FC and fluorescent dyes to monitor the effect that pollutants may exert on Pseudomonas ûuorescens SV3. First we designed an oligotrophic growth test, which enabled us to follow population growth at low densities (104 - 10 7 cells per ml) using 0.1 mM sodium acetate as carbon source. Cells in the oligotrophic milieu were then exposed or not to a variety of common pollutants, such as 2-chlorobiphenyl (2CBP), naphthalene (NAH), 4-chlorophenol (4CP), tetradecane (TD), mercury chloride (HgCl2) or benzene, in different dosages. Exposed culture samples were stained with SYT09 (green fluorescent dye binding nucleic acids, generally staining all cells) in combination with propidium iodide (PI) or ethidium bromide (EB), both dyes being membrane integrity indicators. We ob- served that most of the tested compounds decreased population growth in a dosage- dependent manner. SYT09/PI or SYT09/EB staining then revealed that chemical exposure led to arisal of subpopulations of live and injured or dead cells. By modeling population growth on the total cell numbers in population or only the subpopulation of live cells we inferred that even in stressed populations live cells multiply at rates no different to unexposed controls. The net decrease in population growth would thus be a consequence of more and more cells being not able to multiply at all, rather than all cells multiplying at slower rates. In addition, the proportion of injured cells correlated to the compound dosage. We concluded that the oligotrophic test may be useful to asses toxicity of unknown chemicals on a variety of model bacteria. Mul¬tiple tests can be run in parallel and effects are rapidly measured within a period of 8 hours. Interestingly, in the same exposure tests with P. fluorescens SV3 we observed that some chemicals which did not lead to a reduction of net population growth rates did cause measurable effects on live cells. This was mainly observed in cells within the live subpopulation as an increase of the EB fluorescence signal. We showed that SYT09/EB is a more useful combination of dyes than SYT09/PI because PI fluorescence tend to increase only when cells are effectively dead, but not so much in live cells (less then twofold). In contrast, EB geometric mean fluorescence in live cells increased up to eightfold after exposure to toxic compounds. All compounds even at the lowest concentration caused a measurable increase in EB geometric mean fluorescence especially after 2 h incubation time. This effect was found to be transient for cells exposed to 2CBP and 4CP, but chronic for cells incubated with TD and NAH (ultimately leading to cell death). In order to understand the mechanism underlying the observed effects we used known membrane or energy uncouplers. The pattern of EB signal increase in chemical-exposed populations resembled mostly that of EDTA, although EB fluorescence in EDTA-treated or pasteurized cells was even higher than after exposure to the four test chemicals. We conclude that the ability of cells to efflux EB under equilibrium conditions is an appropriate measure for the potential of a chemical to exert toxicity. Since most bacterial species possess efflux systems for EB that all require cellular energy, our test should be more widely relevant to infer toxicity effects of chemical exposure on the physiological status of the bacterial cell. To better understand the effect of toxicant exposure on efflux defense systems, we studied 2-hydroxybiphenyl toxicity to Pseudomonas azeiaica HBP1. We showed that 2-HBP exerts toxicity even to P. azelaica HBP1, but only at concentrations higher than 0.5 mM. Above this concentration transient loss of membrane polarization and integrity occurred, which we conclude from staining of growing cells with fluorescent dyes. Cells finally recover and resume growth on 2HBP. The high resistance of P. azelaica HBP1 to 2-HBP was found to be the result of an efficient MexABOprM- type efflux pump system counteracting passive influx of this compound into the membrane and cellular interior. Mutants with disrupted mexA, mexB and oprM genes did no longer grow on 2-HBP at concentrations above 100 μΜ, whereas below this concentration we found 2-HBP-concentration dependent decrease of growth rate. The MexAB-OprM system in P. azeiaica HBP1 is indeed an efflux pump for ethidium bromide as well. By introducing gfp reporter fusions responsive to intracellular 2- HBP concentrations into HBP1 wild-type or the mutants we demonstrated that 2HBP enters into the cells in a similar way. In contrast, the reporter system in the wild-type cells does not react to 2-HBP at an outside concentration of 2.4 μΜ, whereas in mutant cells it does. This suggests that wild-type cells pump 2-HBP to the outside very effectively preventing accumulation of 2-HBP. 2HBP metabolism, therefore, is not efficient enough to lower the intracellular concentration and prevent toxicity. We conclude that P. azelaica HBP1 resistance to 2-HBP is mainly due to an efficient efflux system and that 2HBP in high concentrations exerts narcotic effects on the bacterial membrane. In the part of this thesis, we investigated the possibilities of bacteria to degrade pollutants at low concentrations (1 mg per L and below). As test components we used 2-hydroxybiphenyl, antibiotics and a variety of fragrances, many of which are known to be difficult to biodegrade. By using accurate counting of low numbers of bacterial cells we could demonstrate that specific growth on these compounds is possible. We demonstrated the accuracy of FC counting at low cell numbers (down to 103 bacterial cells per ml). Then we tested whether bacterial population growth could be specifically monitored at the expense of low substrate concentrations, us¬ing P. azelaica HBP1. A perfect relationship was found between growth rate, yield and 2-HBP concentrations in the range of 0.1 up to 5 mg per L. Mixing P. azelaica within sludge, however, suggested that growth yields in a mixed community can be much lower than in pure culture, perhaps because of loss of metabolic intermediates. We then isolated new strains from activated sludge using 2-HBP or antibiotics (Nal, AMP, SMX) at low concentrations (0.1-1 mg per L) as sole carbon and energy sub¬strate and PAO microdishes. The purified strains were then examined for growth on their respective substrate, which interestingly, showed that all strains can not with¬stand higher than 1 or 10 mg per L concentrations of target substrate. Thus, bacteria must exist that contribute to compound degradation at low pollutant concentrations but are inhibited at higher concentrations. Finally we tested whether specific biomass growth (in number of cells) at the expense of pollutants can also be detected with communities as starting material. Hereto, we focused on a number of fragrance chemicals and measured community biomass increase by flow cytometry cell counting on two distinct starter communities: (i) diluted Lake Geneva water, and dilute activated sludge from a wastewater treatment plant. We observed that most of the test compounds indeed resulted in significant biomass increase in the starter community compared to a no-carbon added control, but activated sludge and lake Geneva water strongly differed (almost mutually ex¬clusive) in their capacity to degrade the test chemicals. In two cases for activated sludge the same type of microbial community developed upon compound exposure, as concluded from transcription fragment length polymorphism analysis on community purified and PCR amplified 16S rRNA gene fragments. To properly test compound biodegradability it is thus important to use starter communities of different origin. We conclude that FC counting can be a valuable tool to screen chemicals for their biodegradability and toxicity. - Des milliers de produits chimiques sont libérés dans l'environnement mais beaucoup ont des effets inconnus, en particulier à basses concentrations. Ce travail de thèse contribue à notre comprehension des effets de la pollution en utilisant des bacteries comme des organismes-tests. Les bacteries sont importantes pour etudier cette ques¬tion car certaines d'entre elles peuvent degrader ou transformer les polluants, mais également parce qu'elles-mmes peuvent tre inhibees dans leur reproduction après avoit ete exposees à ces composes toxiques. Quand des effets inhibiteurs ont lieu, la composition de la communauté microbienne peut tre changee à long terme, ce qui mène à une reduction du service d'ecosystème offert par ces communautés. En consequence, après leur liberation dans l'environnement, les produits chimiques d'origine anthropogenique peuvent soit s'y accumuler et per¬sister, exerant ainsi des effets encore inconnus sur les organismes vivants. En plus d'acquérir des connaissances de base sur les effets des polluants à basses concentra¬tions sur les communautés microbiennes, un but applique de cette thèse était de développer des tests bases sur les bacteries afin d'identifier de nouveau composes pour leur toxicité ou leur biodégradation. Dans la première partie de ce travail, nous avons developpe un test base sur la cytometrie de flux (FC) sur des cellules de Pseudomonas fluorescens colorees par du bromure d'ethidium ou de l'iodure de propidium et exposees ou non à une palette de polluants sous des conditions de croissance oligotrophique. La cytometrie de flux est une technique qui connaît de nombreuses applications dans la microbiologie environ¬nementale. Cela est principalement du au fait qu'elle permet un comptage rapide et precis ainsi que l'évaluation de l'état physiologique, en particulier lorsqu'elle est combinée h des colorations fluorescentes. Ici, nous avons utilise la technique FC et des colorants fluorescents afin de mesurer l'effet que peuvent exercer certains pollu¬ants sur Pseudomonas ûuorescens SV3 . D'abord nous avons conu des tests oligo- trophiques qui nous permettent de suivre la croissance complète de cellules en culture h des densites faibles (104 -10 7 cellules par ml), sur de l'acetate de sodium à 0.1 mM, en presence ou absence de produits chimiques (2-chlorobiphenyl (2CBP), naphthalène (NAH), 4-chlorophenol (4CP), tetradecane (TD), chlorure de mercure(II) (HgCl2)) à différentes concentrations. Afin de montrer le devenir des bacteries tant au niveau de la cellule individuelle que celui de la population globale, après exposition à des series de composes chimiques, nous avons compte les cellules colorees avec du SYT09 (col¬orant fluorescent vert des acides nucléiques pour la discrimination des cellules par rapport au bruit de fond) en combinaison avec l'iodure de propidium (PI) ou le bromure d'ethidium (EB), indicateurs de l'intégrité de la membrane cellulaire avec FC. Nous avons observe que de nombreux composes testes avaient un effet sur la croissance bacterienne, resultant en une baisse du taux de reproduction de la pop¬ulation. En outre, la double coloration que nous avons utilisee dans cette etude SYT09/PI ou SYT09/EB a montre que les produits chimiques testes induisaient une reponse heterogène des cellules dans la population, divisant celle-ci en sous- populations "saine", "endommagee" ou "morte". Les nombres de cellules à partir du comptage et de la proportion de celles "saines" et "endommagees/mortes" ont ensuite ete utilises pour modeliser la croissance de P. ûuorescens SV3 exposee aux produits chimiques. La reduction nette dans la croissance de population est une consequence du fait que de plus en plus de cellules sont incapables de se reproduire, plutt que du fait d'une croissance plus lente de l'ensemble de la population. De plus, la proportion de cellules endommagees est correllee au dosage du compose chimique. Les résultats obtenus nous ont permis de conclure que le test oligotrophique que nous avons developpe peut tre utilise pour l'évaluation de la toxicité de produits chimiques sur différents modèles bacteriens. Des tests multiples peuvent tre lances en parallèle et les effets sont mesures en l'espace de huit heures. Par ailleurs, nous en déduisons que les produits chimiques exercént un effet sur la croissance des cellules de P. ûuorescens SV3, qui est heterogène parmi les cellules dans la population et depend du produit chimique. Il est intéressant de noter que dans les mmes tests d'exposition avec P. ûuorescens SV3, nous avons observe que certains composes qui n'ont pas conduit à une reduction du taux de la croissance nette de la population, ont cause des effets mesurables sur les cellule saines. Ceci a ete essentiellement observe dans la portion "saine" des cellules en tant qu'augmentation du signal de la fluorescence de 1ΈΒ. D'abord nous avons montre que SYT09/EB était une com¬binaison de colorants plus utile que celle de SYT09/PI parce que la fluorescence du PI a tendance à augmenter uniquement lorsque les cellules sont effectivement mortes, et non pas dans les cellules saines (moins de deux fois plus). Par opposi¬tion, la fluorescence moyenne de l'EB dans les cellules saines augmente jusqu'à huit fois plus après exposition aux composes toxiques. Tous les composes, mme aux plus basses concentrations, induisent une augmentation mesurable de la fluorescence moy¬enne de 1ΈΒ, plus particulièrement après deux heures d'incubation. Cet effet s'est revele tre transitoire pour les cellules exposees aux 2CNP et 4CP, mais est chro¬nique pour les cellules incubees avec le TD et le NAH (entranant la mort cellulaire). Afin de comprendre les mécanismes qui sous-tendent les effets observes, nous avons utilise des decoupleurs d'energie ou de membrane. L'augmentation du signal EB dans les populations causee par des produits chimiques ressemblait à celle exerce par le chelateur des ions divalents EDTA. Cependant, les intensités du signal EB des cellules exposees aux produits chimiques testees n'ont jamais atteint les valeurs des cellules traitees avec l'EDTA ou pasteurises. Nous en concluons que le test oli- gotrophique utilisant la coloration (SYT09/)EB des cellules exposees ou non à un produit chimique est utile afin d'evaluer l'effet toxique exerce par les polluants sur la physiologie bacterienne. Afin de mieux comprendre la reaction d'un système de defense par pompe à efflux après exposition à une toxine, nous avons étudié la toxicité du 2-hydroxybiphenyl (2-HBP) sur Pseudomonas azeiaica HBP1. Nous avons montre que le 2-HBP exerce une toxicité mme sur HBP1, mais uniquement à des concentrations supérieures à 0.5 mM. Au-dessus de cette concentration, des pertes transitoires d'intégrité et de polarization membranaire ont lieu, comme cela nous a ete montre par coloration des cellules en croissance. Les cellules sont finalement capables de se rétablir et de reprendre leur croissance sur 2-HBP. La forte resistance de P. azeiaica HBP1 h 2-HBP physiologie bacterienne s'est revele tre le résultat d'un système de pompe h efflux de type MexABOprM qui contre-balance l'influx passif de ce compose h travers la membrane. Nous avons montre, en construisant des mutants avec des insertions dans les gènes mexA, mexB and oprM et des fusions avec le gène rapporteur gfp, que l'altération de n'importe quelle partie du système d'efflux conduisait à accroître l'accumulation de 2-HBP dans la cellule, en comparaison avec la souche sauvage HBP1, provoquant une diminution de la resistance au 2-HBP ainsi qu'une baisse du taux de reproduction des cellules. Des systèmes d'efflux similaires sont répandus chez de nombreuses espèces bactériennes. Ils seraient responsables de la resistance aux produits chimiques tels que les colorants fluorescents (bromure d'ethidium) et des antibiotiques. Nous concluons que la resistance de P. azelaica HBP1 à 2-HBP est principalement due à un système d'efflux efficace et que 2-HBP, à des concentrations elevees, exerce un effet deletère sur la membrane bacterienne. En se basant sur le comptage des cellules avec la FC, nous avons developpe ensuite une methode pour evaluer la biodegradabilite de polluants tels que le 2-HBP ainsi que les antibiotiques (acide nalidixique (Nal), ampicilline (AMP) ou sulfamethoxazole (SMX)) à de faibles concentrations lmg par L et moins), par le suivi de la croissance spécifique sur le compose de cultures microbiennes pures et mixtes. En utilisant un comptage precis de faibles quantités de cellules nous avons pu demontrer que la croissance spécifique sur ces composes est possible. Nous avons pu illustrer la precision du comptage par cytometrie de flux à faible quantité de cellules (jusqu'à 10 3 cellules par ml). Ensuite, nous avons teste s'il était possible de suivre dynamiquement la croissance de la population de cellules sur faibles concentrations de substrats, en utilisant P. azelaica HBP1. Une relation parfaite a ete trouvee entre le taux de croissance, le rendement et les concentrations de 2-HBP (entre 0.1 et 5 mg par L). En mélangeant HBP1 à de la boue active, nous avons pu montrer que le rendement en communauté mixtes pouvait tre bien inférieur qu'en culture pure. Ceci étant peut tre le résultat d'une perte d'intermédiaires métaboliques. Nous avons ensuite isole de nouvelles souches à partir de la boue active en utilisant le 2-HBP ou des antibiotiques (Nal, AMP, SMX) h basses concentrations (0.1-1 mg par L) comme seules sources de carbone et d'energie. En combinaison avec ceci, nous avons également utilise des microplaques PAO. Les souches purifiees ont ensuite ete examinees pour leurs croissances sur leurs substrats respectifs. De faon intéressante, toutes ces souches ont montre qu'elles ne pouvaient pas survivre à des concentrations de substrats supérieures à 1 ou 10 mg par L. Ainsi, il existe des bacteries qui contribuent à la degradation de composes à basses concentrations de polluant mais sont inhibes lorsque ces concentrations deviennent plus hautes. Finalement, nous avons cherche à savoir s'il est possible de detecter une croissance spécifique à une biomasse au depend d'un polluant, en partant d'une communauté microbienne. Ainsi, nous nous sommes concentre sur certains composes et avons mesure l'augmentation de la biomasse d'une communauté grce à la cytometrie de flux. Nous avons compte deux communautés de depart distinctes: (i) une dilution d'eau du Lac Léman, et une dilution de boue active d'une station d'épuration. Nous avons observe que la plupart des composes testes ont entrane une augmentation de la biomasse de depart par rapport au control sans addition de source de carbone. Néanmoins, les échantillons du lac Léman et de la station d'épuration différaient largement (s'excluant mutuellement l'un l'autre) dans leur capacité à degrader les composes chimiques. Dans deux cas provenant de la station d'épuration, le mme type de communauté microbienne s'est developpe après exposition aux composes, comme l'a démontré l'analyse TRFLP sur les fragments d'ARN 16S purifie de la communauté et amplifie par PCR. Afin de tester correctement la biodegradabilite d'un compose, il est donc important d'utiliser des communautés de depart de différentes origines Nous en concluons que le comptage par cytometrie de flux peut tre un outil de grande utilité pour mettre en valeur la biodegradabillite et la toxicité des composes chimiques.

El problema terminológico de la tutoría entre iguales y la afirmación de su especificidad didáctica

[spa]La tutoría entre iguales ha adquirido un interés creciente en la institución universitaria dentro de la reforma de la educación superior impulsada en las dos últimas décadas. En este contexto, están siendo exploradas las relacio-nes posibles entre el aprendizaje formal y otros tipos diferentes de aprendizaje que se habían mantenido ajenos a la tradición universitaria. Es con la consideración del aprendizaje informal, y en relación con las teorías de las co-munidades de práctica y del aprendizaje situado, que cobra especial relieve la tutoría entre iguales. Este artículo es un estudio teórico sobre dicho recurso didáctico que se centra en dos asuntos fundamentales. Por un lado, el dilu-cidar el complejo problema terminológico que la afecta. Por otro, el subrayar la importancia de sus aportaciones específicas al aprendizaje de los estudiantes. Los dos son esenciales para reivindicar su singularidad y la relevan-cia de sus resultados y, acto seguido, para impulsar su meditada integración en la enseñanza universitaria.

Oppiminen osallistumisen prosessina

Artikkeli pohjautuu Etienne Wengerin teokseen Communities of Practice: Learning, Meaning and Identity (Cambridge University Press, 1998)

Natural variation in learning ability in "Drosophila melanogaster"

Learning is the ability of an organism to adapt to the changes of its environment in response to its past experience. It is a widespread ability in the animal kingdom, but its evolutionary aspects are poorly known. Learning ability is supposedly advantageous under some conditions, when environmental conditions are not too stable - because in this case there is no need to learn to predict any event in the environment - and not changing too fast - otherwise environmental cues cannot be used because they are not reliable. Nevertheless, learning ability is also known to be costly in terms of energy needed for neuronal synthesis, memory formation, initial mistakes. During my PhD, I focused on the study of genetic variability of learning ability in natural populations. Genetic variability is the basis on which natural selection and genetic drift can act. How does learning ability vary in nature? What are the roles of additive genetic variation or maternal effects in this variation? Is it involved in evolutionary trade-offs with other fitness-related traits?¦I investigated a natural population of fruit fly, Drosophila melanogaster, as a model organism. Its learning ability is easy to measure with associative memory tests. I used two research tools: multiple inbred and isofemale lines derived from a natural population as a representative sample. My work was divided into three parts.¦First, I investigated the effects of inbreeding on aversive learning (avoidance of an odor previously associated with mechanical shock). While the inbred lines consistently showed reduced egg-to-adult viability by 28 %, the effects of inbreeding on learning performance was 18 % and varied among assays, with a trend to be most pronounced for intermediate conditioning intensity. Variation among inbred lines indicates that ample genetic variance for learning was segregating in the base population, and suggests that the inbreeding depression observed in learning performance was mostly due to dominance rather than overdominance. Across the inbred lines, learning performance was positively correlated with the egg-to-adult viability. This positive genetic correlation contradicts previous studies which observed a trade-off between learning ability and lifespan or larval competitive ability. It suggests that much of the genetic variation for learning is due to pleiotropic effects of genes affecting other functions related to survival. Together with the overall mild effects of inbreeding on learning performance, this suggests that genetic variation specifically affecting learning is either very low, or is due to alleles with mostly additive (semi-dominant) effects. It also suggests that alleles reducing learning performance are on average partially recessive, because their effect does not appear in the outbred base population. Moreover, overdominance seems unlikely as major cause of the inbreeding depression, because even if the overall mean of the inbred line is smaller than the outbred base population, some of the inbred lines show the same learning score as the outbred base population. If overdominance played an important part in inbreeding depression, then all the homozygous lines should show lower learning ability than¦outbred base population.¦In the second part of my project, I sampled the same natural population again and derived isofemale lines (F=0.25) which are less adapted to laboratory conditions and therefore are more representative of the variance of the natural population. They also showed some genetic variability for learning, and for three other fitness-related traits possibly related with learning: resistance to bacterial infection, egg-to-adult viability and developmental time. Nevertheless, the genetic variance of learning ability did not appear to be smaller than the variance of the other traits. The positive correlation previously observed between learning ability and egg- to-adult viability did not appear in isofemale lines (nor a negative correlation). It suggests that there was still genetic variability within isofemale lines and that they did not fix the highly deleterious pleiotropic alleles possibly responsible for the previous correlation.¦In order to investigate the relative amount of nuclear (additive and non-additive effects) and extra-nuclear (maternal and paternal effect) components of variance in learning ability and other fitness-related traits among the inbred lines tested in part one, I performed a diallel cross between them. The nuclear additive genetic variance was higher than other components for learning ability and survival to learning ability, but in contrast, maternal effects were more variable than other effects for developmental traits. This suggests that maternal effects, which reflects effects from mitochondrial DNA, epigenetic effects, or the amount of nutrients that are invested by the mother in the egg, are more important in the early stage of life, and less at the adult stage. There was no additive genetic correlation between learning ability and other traits, indicating that the correlation between learning ability and egg-to-adult viability observed in the first pat of my project was mostly due to recessive genes.¦Finally, my results showed that learning ability is genetically variable. The diallel experiment showed additive genetic variance was the most important component of the total variance. Moreover, every inbred or isofemale line showed some learning ability. This suggested that alleles impairing learning ability are eliminated by selection, and therefore that learning ability is under strong selection in natural populations of Drosophila. My results cannot alone explain the maintenance of the observed genetic variation. Even if I cannot eliminate the hypothesis of pleiotropy between learning ability and the other fitness-related traits I measured, there is no evidence for any trade-off between these traits and learning ability. This contradicts what has been observed between learning ability and other traits like lifespan and larval competitivity.¦L'apprentissage représente la capacité d'un organisme à s'adapter aux changement de son environnement au cours de sa vie, en réponse à son expérience passée. C'est une capacité très répandue dans le règne animal, y compris pour les animaux les plus petits et les plus simples, mais les aspects évolutifs de l'apprentissage sont encore mal connus. L'apprentissage est supposé avantageux dans certaines conditions, quand l'environnement n'est ni trop stable - dans ce cas, il n'y a rien à apprendre - ni trop variable - dans ce cas, les indices sur lesquels se reposer changent trop vite pour apprendre. D'un autre côté, l'apprentissage a aussi des coûts, en terme de synthèse neuronale, pour la formation de la mémoire, ou de coûts d'erreur initiale d'apprentissage. Pendant ma thèse, j'ai étudié la variabilité génétique naturelle des capacités d'apprentissage. Comment varient les capacités d'apprentissage dans la nature ? Quelle est la part de variation additive, l'impact des effets maternel ? Est-ce que l'apprentissage est impliqué dans des interactions, de type compromis évolutifs, avec d'autres traits liés à la fitness ?¦Afin de répondre à ces questions, je me suis intéressée à la mouche du vinaigre, ou drosophile, un organisme modèle. Ses capacités d'apprentissage sont facile à étudier avec un test de mémoire reposant sur l'association entre un choc mécanique et une odeur. Pour étudier ses capacités naturelles, j'ai dérivé de types de lignées d'une population naturelle: des lignées consanguines et des lignées isofemelles.¦Dans une première partie, je me suis intéressée aux effets de la consanguinité sur les capacités d'apprentissage, qui sont peu connues. Alors que les lignées consanguines ont montré une réduction de 28% de leur viabilité (proportion d'adultes émergeants d'un nombre d'oeufs donnés), leurs capacités d'apprentissage n'ont été réduites que de 18%, la plus forte diminution étant obtenue pour un conditionnement modéré. En outre, j'ai également observé que les capacités d'apprentissage était positivement corrélée à la viabilité entre les lignées. Cette corrélation est surprenante car elle est en contradiction avec les résultats obtenus par d'autres études, qui montrent l'existence de compromis évolutifs entre les capacités d'apprentissage et d'autres traits comme le vieillissement ou la compétitivité larvaire. Elle suggère que la variation génétique des capacités d'apprentissage est due aux effets pleiotropes de gènes récessifs affectant d'autres fonctions liées à la survie. Ces résultats indiquent que la variation pour les capacités d'apprentissage est réduite comparée à celle d'autres traits ou est due à des allèles principalement récessifs. L'hypothèse de superdominance semble peu vraisemblable, car certaines des lignées consanguines ont obtenu des scores d'apprentissage égaux à ceux de la population non consanguine, alors qu'en cas de superdominance, elles auraient toutes dû obtenir des scores inférieurs.¦Dans la deuxième partie de mon projet, j'ai mesuré les capacités d'apprentissage de lignées isofemelles issues de la même population initiale que les lignées consanguines. Ces lignées sont issues chacune d'un seul couple, ce qui leur donne un taux d'hétérozygosité supérieur et évite l'élimination de lignées par fixation d'allèles délétères rares. Elles sont ainsi plus représentatives de la variabilité naturelle. Leur variabilité génétique est significative pour les capacités d'apprentissage, et trois traits liés à la fois à la fitness et à l'apprentissage: la viabilité, la résistance à l'infection bactérienne et la vitesse de développement. Cependant, la variabilité des capacités d'apprentissage n'apparaît cette fois pas inférieure à celle des autres traits et aucune corrélation n'est constatée entre les capacité d'apprentissage et les autres traits. Ceci suggère que la corrélation observée auparavant était surtout due à la fixation d'allèles récessifs délétères également responsables de la dépression de consanguinité.¦Durant la troisième partie de mon projet, je me suis penchée sur la décomposition de la variance observée entre les lignées consanguines observée en partie 1. Quatre composants ont été examinés: la variance due à des effets nucléaires (additifs et non additifs), et due à des effets parentaux (maternels et paternels). J'ai réalisé un croisement diallèle de toutes les lignées. La variance additive nucléaire s'est révélée supérieure aux autres composants pour les capacités d'apprentissage et la résistance à l'infection bactérienne. Par contre, les effets maternels étaient plus importants que les autres composants pour les traits développementaux (viabilité et vitesse de développement). Ceci suggère que les effets maternels, dus à G ADN mitochondrial, à l'épistasie ou à la quantité de nutriments investis dans l'oeuf par la mère, sont plus importants dans les premiers stades de développement et que leur effet s'estompe à l'âge adulte. Il n'y a en revanche pas de corrélation statistiquement significative entre les effets additifs des capacités d'apprentissage et des autres traits, ce qui indique encore une fois que la corrélation observée entre les capacités d'apprentissage et la viabilité dans la première partie du projet était due à des effets d'allèles partiellement récessifs.¦Au, final, mes résultats montrent bien l'existence d'une variabilité génétique pour les capacités d'apprentissage, et l'expérience du diallèle montre que la variance additive de cette capacité est importante, ce qui permet une réponse à la sélection naturelle. Toutes les lignées, consanguines ou isofemelles, ont obtenu des scores d'apprentissage supérieurs à zéro. Ceci suggère que les allèles supprimant les capacités d'apprentissage sont fortement contre-sélectionnés dans la nature Néanmoins, mes résultats ne peuvent pas expliquer le maintien de cette variabilité génétique par eux-même. Même si l'hypothèse de pléiotropie entre les capacités d'apprentissage et l'un des traits liés à la fitness que j'ai mesuré ne peut être éliminée, il n'y a aucune preuve d'un compromis évolutif pouvant contribuer au maintien de la variabilité.

Soil tillage affects the community structure of mycorrhizal fungi in maize roots

In this study we tested whether communities of arbuscular mycorrhizal fungi (AMF) colonizing the roots of maize (Zea mays L.) were affected by soil tillage practices (plowing, chiseling, and no-till) in a long-term field experiment carried out in Tanikon (Switzerland). AMF were identified in the roots using specific polymerase chain reaction (PCR) markers that had been developed for the AMF previously isolated from the soils of the studied site. A nested PCR procedure with primers of increased specificity (eukaryotic, then, fungal, then AMF species or. species-grouop specific) was used. Sequencing of amplified DNA confirmed that the DNA obtained from the maize roots was of AMF origin. Presence of particular AMF species or species-group was scored as a presence of a DNA product after PCR with specific primers. We also used single-strand conformation polymorphism analysis (SSCP), of amplified DNA samples to-check if the amplification of the DNA from maize roots matched the expected profile for a particular AMF isolate with a given specific primer pair. Presence of the genus Scutellospora, in maize roots was strongly reduced in plowed and chiseled soils. Fungi from the suborder Glomineae were more prevalent colonizers of maize roots growing in plowed soils, but were also present in the roots from other tillage treatments. These changes in community of AMF colonizing maize roots might be due to (1), the differences in tolerance to the tillage-induced disruption of the hyphae among the different AMF species, (2) changes in nutrient content of the soil, (3) changes in microbial activity, or (4) changes in weed populations in response to soil tillage. This is the first report on community composition of AMF in the roots of a field-grown crop plant (maize) as affected by soil tillage.