14 research outputs found

    Toxic effect and inability of L-homoserine to be a nitrogen source for growth of Escherichia coli resolved by a combination of in vivo evolution engineering and omics analyses

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    L-homoserine is a pivotal intermediate in the carbon and nitrogen metabolism of E. coli. However, this non-canonical amino acid cannot be used as a nitrogen source for growth. Furthermore, growth of this bacterium in a synthetic media is potently inhibited by L-homoserine. To understand this dual effect, an adapted laboratory evolution (ALE) was applied, which allowed the isolation of a strain able to grow with L-homoserine as the nitrogen source and was, at the same time, desensitized to growth inhibition by this amino acid. Sequencing of this evolved strain identified only four genomic modifications, including a 49 bp truncation starting from the stop codon of thrL. This mutation resulted in a modified thrL locus carrying a thrL* allele encoding a polypeptide 9 amino acids longer than the thrL encoded leader peptide. Remarkably, the replacement of thrL with thrL* in the original strain MG1655 alleviated L-homoserine inhibition to the same extent as strain 4E, but did not allow growth with this amino acid as a nitrogen source. The loss of L-homoserine toxic effect could be explained by the rapid conversion of L-homoserine into threonine via the thrL*-dependent transcriptional activation of the threonine operon thrABC. On the other hand, the growth of E. coli on a mineral medium with L-homoserine required an activation of the threonine degradation pathway II and glycine cleavage system, resulting in the release of ammonium ions that were likely recaptured by NAD(P)-dependent glutamate dehydrogenase. To infer about the direct molecular targets of L-homoserine toxicity, a transcriptomic analysis of wild-type MG1655 in the presence of 10 mM L-homoserine was performed, which notably identified a potent repression of locomotion-motility-chemotaxis process and of branched-chain amino acids synthesis. Since the magnitude of these effects was lower in a ΔthrL mutant, concomitant with a twofold lower sensitivity of this mutant to L-homoserine, it could be argued that growth inhibition by L-homoserine is due to the repression of these biological processes. In addition, L-homoserine induced a strong upregulation of genes in the sulfate reductive assimilation pathway, including those encoding its transport. How this non-canonical amino acid triggers these transcriptomic changes is discussed

    Workshop Xenakis. Entre les mondes, une expérimentation architecture/musique

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    Le Workshop architecture et musique – « Xenakis, entre les mondes » (janvier 2019) a conduit une Ă©quipe interdisciplinaire Ă  rĂ©aliser une expĂ©rience collective in situ : architectes, musiciens, compositeurs, artistes plasticiens, vidĂ©astes ont cherchĂ© Ă  expĂ©rimenter les croisements Architecture / Musique, considĂ©rer l’Ɠil avec l’oreille, et le corps humain tout entier, rĂ©aliser des Ă©chantillons, des structures multimĂ©dia, un « entre les mondes » selon la thĂ©matique de l’exposition IannisXenakis, entre les mondesau Learning center de Dunkerque (12 janvier-28 fĂ©vrier 2019) et l’ouvrage de SĂ©verine BRIDOUX-MICHEL, Le Corbusier & Iannis Xenakis. Un dialogue architecture-musique (Ă©ditions Imbernon, 2018). Pendant une semaine, il s’agissait de rĂ©aliser des travaux expĂ©rimentaux en immersion Ă  l’ESA Hauts-de-France de Dunkerque et reposer la question du dispositif scĂ©nique traditionnel, de la relation entre le public et les artistes. Ce Workshop a permis de tester collectivement in situ des propositions spatiales, visuelles et sonores

    Automated and multiplexed soft lithography for the production of low-density DNA microarrays

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    International audienceMicroarrays are established research tools for genotyping, expression profiling, or molecular diagnostics in which DNA molecules are precisely addressed to the surface of a solid support. This study assesses the fabrication of low-density oligonucleotide arrays using an automated microcontact printing device, the InnoStamp 40(Ÿ). This automate allows a multiplexed deposition of oligoprobes on a functionalized surface by the use of a MacroStamp(TM) bearing 64 individual pillars each mounted with 50 circular micropatterns (spots) of 160 ”m diameter at 320 ”m pitch. Reliability and reuse of the MacroStamp(TM) were shown to be fast and robust by a simple washing step in 96% ethanol. The low-density microarrays printed on either epoxysilane or dendrimer-functionalized slides (DendriSlides) showed excellent hybridization response with complementary sequences at unusual low probe and target concentrations, since the actual probe density immobilized by this technology was at least 10-fold lower than with the conventional mechanical spotting. In addition, we found a comparable hybridization response in terms of fluorescence intensity between spotted and printed oligoarrays with a 1 nM complementary target by using a 50-fold lower probe concentration to produce the oligoarrays by the microcontact printing method. Taken together, our results lend support to the potential development of this multiplexed microcontact printing technology employing soft lithography as an alternative, cost-competitive tool for fabrication of low-density DNA microarrays

    Dynamic PDMS inking for DNA patterning by soft lithography

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    International audienceMicrocontact printing (ÎŒCP) is used as a patterning technique to produce simple, rapid and cost-effective DNA microarrays. The accuracy of the final transferred pattern drastically depends on the inking step. The usual way to ink a PDMS stamp by droplet deposition of labeled biomolecules using a pipette, results in irregular transfer of the biomolecules on the chip surface and leads to poor and irreproducible fluorescent signals. These drawbacks are likely due to irregular ‘coating’ of the biomolecules on the PDMS stamp. In this work, a novel approach for inking PDMS with DNA molecules is presented. It is based on the continuous displacement of the meniscus formed by the inking solution over the surface of the stamp. When compared with the conventional technique, this dynamic PDMS inking method proved to be very reproducible for producing regular prints/spots on a functionalized glass slide, and this method could be easily extrapolated at an industrial scale

    Entre les mondes, Iannis Xenakis

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    Le travail xenakien pose la question des frontiĂšres et de leur franchissement. De l’architecture Ă  la musique, de la thĂ©orie Ă  la pratique, de l’art Ă  la science, Iannis Xenakis montra l’exemple d’une libre circulation, toujours guidĂ© par les lois de la Nature, si ce n’est par une visĂ©e universelle de la crĂ©ation. Musique environnementale/architecture immatĂ©rielle, concepts et symboles dans l’ƒuvre xenakien, dialectique architecture/musique : trois volets du prĂ©sent ouvrage, articulĂ©s autour de la thĂ©matique entre les mondes, visent Ă  dĂ©finir et mettre en perspective un « entre les mondes » dans le travail de conception, d’invention, de crĂ©ation, de composition, non seulement de Iannis Xenakis, mais aussi de toutes celles et tous ceux pour lesquels ce citoyen des mondes peut constituer une rĂ©fĂ©rence.From architecture to music, from theory to practice, from art to science, Iannis Xenakis set an example of free movement, always guided by a universal aim of creation
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