Bacterial Evolution: Rewiring Modules to Get in Shape

SummaryBacterial species take on a wide variety of shapes, but the mechanisms by which specific shapes evolve have remained poorly understood. A recent study demonstrates that two Asticcacaulis species repurposed an ancestral regulatory protein to rewire the modules of stalk regulation, localization, and synthesis, thereby generating new shapes

Spectres et corpus d’une nouvelle langue maternelle

L’hébreu est une nouvelle langue maternelle dont le fondement est spirituel, culturel et religieux. Comment est-elle édifiée ? Existe-t-il dans ce langage spécifique à la transmission de vive voix entre générations, des versions, essais, tentatives, explorations ou expérimentations qui pourraient retracer ce processus ? L’étude des facettes d’Éliezer Ben-Yehuda, figure de la « résurrection » de l’hébreu ainsi que l’étude du corpus singulier de sa bibliothèque personnelle permettra d’explorer le fondement du texte dans la langue maternelle hébraïque

Spectra and Corpora of a New Mother Tongue

An everyday secular language whose basis is spiritual, cultural and religious, Hebrew, assesses the genesis of a contemporary mother tongue. How is a new mother tongue formed? Are there, in this specific language of verbal transmission between generations, versions, attempts, explorations or experiments, which could trace this process? The study of multifaceted Eliezer Ben-Yehuda, figure of the "resurrection" of Hebrew, as well as the study of the corpus of his personal library, allow us to explore the essential place of the text in the Hebraic mother tongue

A novel neuropathic pain treatment: achieving neuronal inhibition with a split ring resonator

Neuropathic pain is commonly the result of lesions, nervous dysfunction, and/or surgical injury, debilitating a significant portion of the population through conditions like multiple sclerosis or sciatica . Neuromodulatory treatments to address false, exaggerated, or unusual signals focus on areas upstream of the dysfunctional site, but are often some combination of highly invasive, wired power, and stimulation rather than inhibition. This study was performed with a microwave-coupled split ring resonator (SRR), a cornerstone of metamaterials manipulations, to achieve minimally invasive, wireless, submillimeter precision neural inhibition for potential pain applications with no supplementary modifications. Procambarus clarkii was used as a microwave-compatible ex vivo testing platform with extracellular neuronal electrophysiology capturing multiple axons simultaneously. A custom analysis suite was also created to determine changes in action potential characteristics as a metric for successful inhibition. The results of this thesis lay foundations for further study on neuromodulation with the microwave SRR and highlight necessary changes for future in vivo use

Surface Attachment Induces Pseudomonas aeruginosa Virulence

Pseudomonas aeruginosa infects every type of host that has been examined by deploying multiple virulence factors. Previous studies of virulence regulation have largely focused on chemical cues, but P. aeruginosa may also respond to mechanical cues. Using a rapid imaging-based virulence assay, we demonstrate that P. aeruginosa activates virulence in response to attachment to a range of chemically distinct surfaces, suggesting that this bacterial species responds to mechanical properties of its substrates. Surface-activated virulence requires quorum sensing, but activating quorum sensing does not induce virulence without surface attachment. The activation of virulence by surfaces also requires the surface-exposed protein PilY1, which has a domain homologous to a eukaryotic mechanosensor. Specific mutation of the putative PilY1 mechanosensory domain is sufficient to induce virulence in non-surface-attached cells, suggesting that PilY1 mediates surface mechanotransduction. Triggering virulence only when cells are both at high density and attached to a surface—two host-nonspecific cues—explains how P. aeruginosa precisely regulates virulence while maintaining broad host specificity

Stigma, Marginalization and Psychosocial Wellbeing of Orphans in Rwanda : Exploring the Mediation Role of Social Support

Peer reviewe

PSICIC: Noise and Asymmetry in Bacterial Division Revealed by Computational Image Analysis at Sub-Pixel Resolution

Live-cell imaging by light microscopy has demonstrated that all cells are spatially and temporally organized. Quantitative, computational image analysis is an important part of cellular imaging, providing both enriched information about individual cell properties and the ability to analyze large datasets. However, such studies are often limited by the small size and variable shape of objects of interest. Here, we address two outstanding problems in bacterial cell division by developing a generally applicable, standardized, and modular software suite termed Projected System of Internal Coordinates from Interpolated Contours (PSICIC) that solves common problems in image quantitation. PSICIC implements interpolated-contour analysis for accurate and precise determination of cell borders and automatically generates internal coordinate systems that are superimposable regardless of cell geometry. We have used PSICIC to establish that the cell-fate determinant, SpoIIE, is asymmetrically localized during Bacillus subtilis sporulation, thereby demonstrating the ability of PSICIC to discern protein localization features at sub-pixel scales. We also used PSICIC to examine the accuracy of cell division in Esherichia coli and found a new role for the Min system in regulating division-site placement throughout the cell length, but only prior to the initiation of cell constriction. These results extend our understanding of the regulation of both asymmetry and accuracy in bacterial division while demonstrating the general applicability of PSICIC as a computational approach for quantitative, high-throughput analysis of cellular images

Surface association sensitizes Pseudomonas aeruginosa to quorum sensing

In the pathogen Pseudomonas aeruginosa, LasR is a quorum sensing (QS) master regulator that senses the concentration of secreted autoinducers as a proxy for bacterial cell density. Counterintuitively, previous studies showed that saturating amounts of the LasR ligand, 3OC12-HSL, fail to induce the full LasR regulon in low-density liquid cultures. Here we demonstrate that surface association, which is necessary for many of the same group behaviors as QS, promotes stronger QS responses. We show that lasR is upregulated upon surface association, and that surface-associated bacteria induce LasR targets more strongly in response to autoinducer than planktonic cultures. This increased sensitivity may be due to surface-dependent lasR induction initiating a positive feedback loop through the small RNA, Lrs1. The increased sensitivity of surface-associated cells to QS is affected by the type IV pilus (TFP) retraction motors and the minor pilins. The coupling of physical surface responses and chemical QS responses could enable these bacteria to trigger community behaviors more robustly when they are more beneficial