Bacteriophage Tubulins: Carrying Their Own Cytoskeleton Key

SummaryCytoskeletal elements are well known to be widespread in eukaryotes and prokaryotes, providing important, diverse functions for cells large and small. Two new studies report that some bacteriophages encode their own tubulin homologs to facilitate phage reproduction within the host cell

Réflexions sur les limites d'une intégration langues-savoirs disciplinaires entre milieux étrangers

Dans le cadre des programmes européens, les étudiants suivent les enseignements de leur spécialité directement en langue étrangère dans le contexte institutionnel du pays d’accueil. Pour ceux dont la formation associe une, voire deux langues cibles et des disciplines d’application telles que l’économie et le droit, dans lesquelles leur degré d’expertise est encore modeste, la question des modes d’interaction entre savoir-faire langagiers et savoirs disciplinaires, des processus cognitifs qui entrent en jeu, se présente de façon particulièrement complexe. Une première enquête fait ressortir une forte association entre les savoirs disciplinaires et les langues qui les ont véhiculés, un manque de perméabilité inter-langues et une difficulté à réintégrer les acquis dans le contexte de la langue maternelle.In the framework of European programmes, students study their specialized subjects in the language and in the institutional context of the host country. For those whose curriculum includes one or even two foreign languages together with applied subjects such as economics and law, in which their expertise is still limited, the problem of a possible interaction between their language skills and their acquisitions in the applied subjects, and the problem of the cognitive processes which come into play, are particularly difficult to identify. A preliminary survey shows a close connection between their knowledge in the disciplines and the languages in which they were studied, very little cross-transfer between the languages and difficulty in using the acquired knowledge in the relevant context in their mother tongue

Anchors: A Way for FtsZ Filaments To Stay Membrane Bound

Most bacteria use the tubulin homolog FtsZ to organize their cell division. FtsZ polymers initially assemble into mobile complexes that circle around a ring-like structure at the cell midpoint, followed by the recruitment of other proteins that will constrict the cytoplasmic membrane and synthesize septal peptidoglycan to divide the cell. Despite the need for FtsZ polymers to associate with the membrane, FtsZ lacks intrinsic membrane binding ability. Consequently, FtsZ polymers have evolved to interact with the membrane through adaptor proteins that both bind FtsZ and the membrane. Here, we discuss recent progress in understanding the functions of these FtsZ membrane tethers. Some, such as FtsA and SepF, are widely conserved and assemble into varied oligomeric structures bound to the membrane through an amphipathic helix. Other less-conserved proteins, such as EzrA and ZipA, have transmembrane domains, make extended structures, and seem to bind to FtsZ through two separate interactions. This review emphasizes that most FtsZs use multiple membrane tethers with overlapping functions, which not only attach FtsZ polymers to the membrane but also organize them in specific higher-order structures that can optimize cell division activity. We discuss gaps in our knowledge of these concepts and how future studies can address them

Tonic Inhibition Enhances Fidelity of Sensory Information Transmission in the Cerebellar Cortex

Tonic inhibition is a key regulator of neuronal excitability and network function in the brain, but its role in sensory information processing remains poorly understood. The cerebellum is a favorable model system for addressing this question as granule cells, which form the input layer of the cerebellar cortex, permit high-resolution patch-clamp recordings in vivo, and are the only neurons in the cerebellar cortex that express the α6δ-containing GABA(A) receptors mediating tonic inhibition. We investigated how tonic inhibition regulates sensory information transmission in the rat cerebellum by using a combination of intracellular recordings from granule cells and molecular layer interneurons in vivo, selective pharmacology, and in vitro dynamic clamp experiments. We show that blocking tonic inhibition significantly increases the spontaneous firing rate of granule cells while only moderately increasing sensory-evoked spike output. In contrast, enhancing tonic inhibition reduces the spike probability in response to sensory stimulation with minimal effect on the spontaneous spike rate. Both manipulations result in a reduction in the signal-to-noise ratio of sensory transmission in granule cells and of parallel fiber synaptic input to downstream molecular layer interneurons. These results suggest that under basal conditions the level of tonic inhibition in vivo enhances the fidelity of sensory information transmission through the input layer of the cerebellar cortex

Molecular bases determining daptomycin resistance-mediated re-sensitization to β-lactams ("see-saw effect") in MRSA

Antimicrobial resistance is recognized as one of the principal threats to public health worldwide, yet the problem is increasing. Methicillin-resistant Staphylococcus aureus (MRSA) are among the most difficult to treat in clinical settings due to the resistance to nearly all available antibiotics. The cyclic anionic lipopeptide antibiotic Daptomycin (DAP) is the clinical mainstay of anti-MRSA therapy. Decreased susceptibility to DAP (DAPR) reported in MRSA is frequently accompanied with a paradoxical decrease in β-lactam resistance, a process known as the "see-saw" effect. Despite the observed discordance in resistance phenotypes, the combination of DAP/β-lactams has been proven clinically effective for the prevention and treatment of infections due to DAPR-MRSA strains. However, the mechanisms underlying the interactions between DAP and β-lactams are largely unknown. Herein, we studied the role of DAP-induced mutated mprF in β-lactam sensitization and its involvement in the effective killing by the DAP/OXA combination. DAP/OXA-mediated effects resulted in cell-wall perturbations including changes in peptidoglycan (PG) insertion, penicillin-binding protein 2 (PBP2) delocalization and reduced membrane amounts of penicillin-binding protein 2a (PBP2a) contents despite increased transcription of mecA through mec regulatory elements. We have found that the VraSR sensor-regulator is a key component of DAP resistance, triggering mutated mprF-mediated cell membrane (CM) modifications and resulting in impairment of PrsA location and chaperone functions, both essentials for PBP2a maturation, the key determinant of β-lactam resistance. These observations provide first time evidence that synergistic effects between DAP and β-lactams involve PrsA post-transcriptional regulation of CM-associated PBP2a

Phase chaos in the anisotropic complex Ginzburg-Landau Equation

Of the various interesting solutions found in the two-dimensional complex Ginzburg-Landau equation for anisotropic systems, the phase-chaotic states show particularly novel features. They exist in a broader parameter range than in the isotropic case, and often even broader than in one dimension. They typically represent the global attractor of the system. There exist two variants of phase chaos: a quasi-one dimensional and a two-dimensional solution. The transition to defect chaos is of intermittent type.Comment: 4 pages RevTeX, 5 figures, little changes in figures and references, typos removed, accepted as Rapid Commun. in Phys. Rev.