Une entité scientifique, tout en ayant son propre devenir dans le domaine scientifique, s’étend aussi souvent à d’autres domaines d’activité. Parallèlement à la diffusion des découvertes scientifiques, elle peut susciter un intérêt artistique ou conceptuel. Les études sur le microbiome humain ont nourri un tel intérêt pour les microbes et ont encouragé de nombreux artistes à entrer dans un laboratoire de biologie et à produire des oeuvres artistiques avec et à travers les microbes. Ces oeuvres d’art établissent une relation étroite avec les découvertes scientifiques récentes, les procédures et les protocoles, et posent des questions philosophiques sur la vie et la mort, la nature, l’humanité, et les relations entre les êtres vivants. Cette thèse vise à examiner les processus sociaux, techniques, politiques et économiques qui traversent les sciences des microbes et à déterminer comment ils aboutissent dans les oeuvres d’Elaine Whittaker, Tarsh Bates, François-Joseph Lapointe, Günes-Helen Isitan, le collectif Interspecifics, Victoria Shennan, Saša Spačal, Sonja Bäumel, Raphael Kim et Kathy High. Lorsque nous trouvons un microbe dans un contexte particulier, que trouvons-nous d’autre avec lui ? Dans quelles conditions apparaît-il dans une oeuvre d’art et avec quels éléments l’oeuvre compose-t-elle pour produire des effets esthétiques ? Dans cette thèse, l’histoire des microbes considérée du point de vue des formes d’art les mobilisant (ou « microbe-oeuvres d’art » pour microbe-artworks) commence en fait avec des animalcules qui n’étaient pas encore des entités scientifiques à part entière, mais qui présentaient virtuellement les forces qui seraient réunies plus tard sous le terme scientifique de « microbe ». Dans un premier temps, les animalcules, nommés après des observations d’Antonie von Leeuwenhoek, ont suscité l’intérêt de philosophes comme Leibniz et Spinoza et intensifié la curiosité de peintres comme Johannes Vermeer pour les éléments microscopiques de la vision, initiant ainsi des voyages entre les champs scientifiques et artistiques. Cette étude propose de problématiser ces voyages à l’aide du concept d’« échologie », un terme oublié d’une thèse écrite dans les années 1970 par Jean Milet sur la sociologie de Gabriel Tarde. Mais les théories d’autres philosophes tels que Georges Canguilhem, Michel Foucault, Gilles Deleuze, Félix Guattari, Marie-José Mondzain, et Gilbert Simondon, et des penseurs contemporains tels que Thierry Bardini et Brian Massumi sont également mobilisées pour donner à ce terme toute sa cohérence. Selon l’échologie, les entités sont constituées des motifs (patterns) d’interférence et de résonance avec d’autres choses, qui précèdent leur représentation. Ainsi, une 5 entité donnée est un complexe de forces, et son apparition, le résultat de certaines techniques qui la mettent en relation avec d’autres complexes ne peut s’expliquer comme un effet associé à une seule cause, mais se donne comme un effet supplémentaire, un extra-effet ou un surplus qui laisse toujours une trace ou un résidu. D’un point de vue échologique, une microbe-oeuvre d’art s’opère comme une interface qui intègre des potentiels qui se rendent visibles à travers les traces en vertu de multiples processus recoupant les activités scientifiques et les stratégies artistiques. Chaque chapitre de la thèse est ainsi une étape dans un voyage conceptuel expérimental, révélant les dimensions des oeuvres d’art considérées au regard de l’analyse de ces traces. Au cours de ce voyage, les éléments des théories scientifiques concernées, des entretiens avec des artistes, des sorties sur des sites de pratique des arts biologiques, lors d’ateliers, de conférence et d’écoles d’été sont mobilisés comme facteurs contribuant à la construction des champs problématiques dans chaque chapitre. Les microbes considérés comme des objets de beauté apparaissent comme le résultat d’une transformation discursive des sciences biologiques. D’une conception pathogène des microbes aux approches écologiques, l’iconicité des microbes associés aux microbe-images, l’échologie des microbe-sons, le devenir-milieu de certaines microbe-oeuvres d’art, et enfin la question de l’individuation de la pensée, et l’éthique corrélée compris comme le problème de la valorisation des microbes dans des microbe-oeuvres d’art, le devenir-microbe découle de cette transformation discursive à travers le champ artistique. / A scientific entity, while having its own becoming in the scientific field, often also spreads to other fields of activity, such as art and philosophy. Microbiome studies fed such an interest towards microbes and encouraged many artists to enter a biology laboratory and produce a work of art with and through microbes. These artworks establish a close relationship with recent scientific findings, procedures and protocols, and ask philosophical questions about life and death, nature, humanness, and the relationships between living beings. This thesis aims to examine the social, technical, political, and economic processes that go through the microbe sciences and determine how they come together in the artworks of Elaine Whittaker, Tarsh Bates, François-Joseph Lapointe, Günes-Helen Isitan, the collective Interspecifics, Victoria Shennan, Saša Spačal, Sonja Bäumel, Raphael Kim, and Kathy High. When we find a microbe in a particular context, what else do we find with it? Under which conditions does it appear in an artwork and which elements does the artwork compose with to produce aesthetic effects? In this thesis, the story of microbes is recounted from the perspective of microbe-artworks and starts with animalcules, the not yet full-fledged scientific entity which virtually present the forces that would be brought together under the scientific term “microbe”. At first, animalcules––named after Antonie van Leeuwenhoek’s observations, attracted the interest of philosophers such as Leibniz and Spinoza and intensified the curiosity of painters such as Johannes Vermeer towards the microscopic elements of seeing, hereby initiating journeys between scientific and artistic fields. This study proposes to problematize these journeys as an “echology”. Echology is a forgotten term first introduced in the ‘70s by Jean Milet in his thesis about the sociology of Gabriel Tarde. Here, the theories of other philosophers such as Georges Canguilhem, Michel Foucault, Gilles Deleuze, Félix Guattari, Marie-José Mondzain, Gilbert Simondon, and contemporary thinkers such as Thierry Bardini and Brian Massumi are mobilized in order to give this term its full consistency. According to echology, entities consist of patterns of interference and resonance with other things, which arise before their representation. Thus, a given entity is a complex of forces and its apparition the result of certain techniques which put it into relation with other complexes cannot be explained as an effect associated with a single cause but gives itself as an extra-effect or surplus that always leaves a remainder. From an echological perspective, a microbe- 7 artwork operates as an interface that incorporates potentials that make themselves visible through the remainders by virtue of multiple processes cutting across scientific activities and artistic strategies. Each chapter of the thesis is thus a way station in a conceptual journey of experimentation, revealing the dimensions of the artworks under consideration with respect to the analysis of these remainders. During this journey, elements of scientific theories, interviews with artists, field trips to sites of practice of the biological arts, related workshops and summer schools are mobilized as contributory factors of the construction of the problematic fields in each chapter. Microbes considered as objects of beauty hence appear as the result of discursive transformation of biological sciences. From earlier pathogenic conceptions of microbes to contemporary ecological approaches, the iconicity of microbes associated with microbe-images, echology of microbe-sounds, becoming-milieu of certain microbe-artworks, and finally, the question of individuation of thought and the correlated ethics understood as the problem of valuation of microbe-artworks, the becoming-microbe stems from this discursive transformation through the art field.

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<p>  </p> <p>Plant roots form an intimate relationship with a diversity of soil microorganisms. Some soil-borne microbes cause harmful diseases on crops, but others promote plant growth and enhance host resilience against stressors. Beneficial bacteria have a high potential as a strategy for sustainable agricultural management, many of which have been recognized and commercialized for improving crop growth. Unfortunately, field inoculants of beneficial bacteria often give inconsistent results due to various environmental factors hindering their beneficial properties. Improving crop production utilizing beneficial bacteria requires two approaches: 1) breeding for crops with the enhanced association for beneficial bacteria and 2) improving formulation methods for producing more potent microbial products. To contribute to these goals, we address three critical questions utilizing the tomato root microbiome as a model system. First, we asked how beneficial root-associated bacteria could be efficiently identified. We developed a strategy to select beneficial bacteria from a novel collection of 183 bacterial endophytes isolated from roots of two field-grown tomato species. The results suggest that isolates with similar traits impact plant growth at the same levels, regardless of their taxonomic classification or host origin. Next, we asked whether host genetics contribute to the root microbiome assembly and response to beneficial microbes. An assessment of the root microbiome profile and plant binary interaction experiments suggested the role of host genetics in influencing root recruitment and response to beneficial bacteria. Subsequently, we asked whether root-associated bacteria induce physiological changes in root tissues in the host. We identified two isolates from our bacterial endophyte collection that significantly promoted the growth of tomato genotype H7996 (<em>Solanum lycopersicum</em>). Plant-binary interaction experiments suggested a significant increase of cell wall lignification in the root vasculature starting 96-hour post-inoculation with beneficial bacteria. Additional studies are needed to uncover a possible correlation between the induced vasculature lignification and the growth-promoting effects of the two isolates on H7996. Altogether, our findings highlight the multi-faceted role of root-associated bacteria in promoting plant growth and support the development of crop improvement strategies in optimizing host association with soil bacteria.</p>

Arbuscular mycorrhizal (AM) symbiosis modulates plant‐herbivore interactions. Still, how it shapes the overall plant defence strategy and the mechanisms involved remain unclear. We investigated how AM symbiosis simultaneously modulates plant resistance and tolerance to a shoot herbivore, and explored the underlying mechanisms. Bioassays with Medicago truncatula plants were used to study the effect of the AM fungus Rhizophagus irregularis on plant resistance and tolerance to Spodoptera exigua herbivory. By performing molecular and chemical analyses, we assessed the impact of AM symbiosis on herbivore‐triggered phosphate (Pi)‐ and jasmonate (JA)‐related responses. Upon herbivory, AM symbiosis led to an increased leaf Pi content by boosting the mycorrhizal Pi‐uptake pathway. This enhanced both plant tolerance and herbivore performance. AM symbiosis counteracted the herbivore‐triggered JA burst, reducing plant resistance. To disentangle the role of the mycorrhizal Pi‐uptake pathway in the plant's response to herbivory, we used the mutant line ha1‐2, impaired in the H+‐ATPase gene HA1, which is essential for Piuptake via the mycorrhizal pathway. We found that mycorrhiza‐triggered enhancement of herbivore performance was compromised in ha1‐2 plants. AM symbiosis thus affects the defence pattern of M. truncatula by altering resistance and tolerance simultaneously. We propose that the mycorrhizal Pi‐uptake pathway is involved in the modulation of the plant defence strategy.

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