Proteolysis-Dependent Remodeling of the Tubulin Homolog FtsZ at the Division Septum in \u3ci\u3eEscherichia coli\u3c/i\u3e

During bacterial cell division a dynamic protein structure called the Z-ring assembles at the septum. The major protein in the Z-ring in Escherichia coli is FtsZ, a tubulin homolog that polymerizes with GTP. FtsZ is degraded by the two-component ATP-dependent protease ClpXP. Two regions of FtsZ, located outside of the polymerization domain in the unstructured linker and at the C-terminus, are important for specific recognition and degradation by ClpXP. We engineered a synthetic substrate containing green fluorescent protein (Gfp) fused to an extended FtsZ C-terminal tail (residues 317–383), including the unstructured linker and the C-terminal conserved region, but not the polymerization domain, and showed that it is sufficient to target a non-native substrate for degradation in vitro. To determine if FtsZ degradation regulates Z-ring assembly during division, we expressed a full length Gfp-FtsZ fusion protein in wild type and clp deficient strains and monitored fluorescent Z-rings. In cells deleted for clpX or clpP, or cells expressing protease-defective mutant protein ClpP(S97A), Z-rings appear normal; however, after photobleaching a region of the Z-ring, fluorescence recovers ~70% more slowly in cells without functional ClpXP than in wild type cells. Gfp-FtsZ(R379E), which is defective for degradation by ClpXP, also assembles into Z-rings that recover fluorescence ~2-fold more slowly than Z-rings containing Gfp-FtsZ. In vitro, ClpXP cooperatively degrades and disassembles FtsZ polymers. These results demonstrate that ClpXP is a regulator of Z-ring dynamics and that the regulation is proteolysis-dependent. Our results further show that FtsZ-interacting proteins in E. coli fine-tune Z-ring dynamics

Physiologie de l'espèce : histoire de la génération de l'homme : comprenant l'etude comparative de cette fonction dans les divisions principales du regne animal : l'analyse des causes et du traitement de l'impuissance et de la stérilité et l'exposé des motifs qui ont présidé a la rédaction de plusieurs lois concernant la famille e le citoyen

AntepAs il. en cor e negr

Proteomic analysis of Marinobacter hydrocarbonoclasticus SP17 biofilm formation at the alkane-water interface reveals novel proteins and cellular processes involved in hexadecane assimilation

International audienceMany hydrocarbon-degrading bacteria form biofilms at the hydrocarbon-water interface to overcome the weak accessibility of these poorly water-soluble substrates. In order to gain insight into the cellular functions involved, we undertook a proteomic analysis of Marinobacter hydrocarbonoclasticus SP17 biofilm developing at the hexadecane-water interface. Biofilm formation on hexadecane led to a global change in cell physiology involving modulation of the expression of 576 out of 1144 detected proteins when compared with planktonic cells growing on acetate. Biofilm cells overproduced a protein encoded by MARHY0478 that contains a conserved domain belonging to the family of the outer membrane transporters of hydrophobic compounds. Homologs of MARHY0478 were exclusively found in marine bacteria degrading alkanes or possessing alkane degradation genes, and hence presumably constitute a family of alkane transporters specific to marine bacteria. Interestingly, we also found that sessile cells growing on hexadecane overexpressed type VI secretion system components. This secretion system has been identified as a key factor in virulence and in symbiotic interaction with host organisms. This observation is the first experimental evidence of the contribution of a type VI secretion system to environmental adaptation, and raises the intriguing question about the role of this secretion machine in alkane assimilation

The marine bacterium Marinobacter hydrocarbonoclasticus SP17 degrades a wide range of lipids and hydrocarbons through the formation of oleolytic biofilms with distinct gene expression profiles.

International audienceHydrophobic organic compounds (mainly lipids and hydrocarbons) represent a significant part of the organic matter in the marine waters and their degradation has thus an important impact in the carbon fluxes within the oceans. However, because they are nearly insoluble in the water phase, their degradation by microorganisms occurs at the interface with water therefore requiring specific adaptations like biofilm formation. We show that Marinobacter hydrocarbonoclasticus SP17 develops biofilms, referred as oleolytic biofilms, on a larger variety of hydrophobic substrates than suspected before, including hydrocarbons, fatty alcohols, fatty acids, triglycerides and wax esters. A microarray analysis confirmed that biofilm growth on n-hexadecane or triolein involved distinct genetic responses together with a core of common genes that might concern general mechanisms of biofilm formation. Biofilm growth on triolein modulated the expression of hundreds of genes in comparison to n36hexadecane. Processes related to primary metabolism and genetic information processing were down-regulated. Most of the genes over-expressed on triolein had unknown function. Surprisingly, their genome localization is restricted to a few regions identified as putative genomic islands or mobile elements. These results are discussed with regard to the adaptive responses triggered by M. hydrocarbonoclasticus SP17 to occupy a specific niche in marine ecosystems

Ġustizzja

Ġabra ta’ poeżiji u proża li tinkludi: L-istorja ta’ Ġużepp l-iswed ta’ Ġ. Aquilina – Lil Madliena ta’ Ġ. Micallef Grimaud – Qabel il-lejl ta’ Joseph M. Ciappara – Aqta’ jiesek li tarani... ta’ A. Cremona – Pagliaccio ta’ W. P. G. – Ġustizzja ta’ V. C.N/

Calcium-activated chloride channels clamp odor-evoked spike activity in olfactory receptor neurons

The calcium-activated chloride channel anoctamin-2 (Ano2) is thought to amplify transduction currents in olfactory receptor neurons (ORNs), a hypothesis supported by previous studies in dissociated neurons from Ano2-/- mice. Paradoxically, despite a reduction in transduction currents in Ano2-/- ORNs, their spike output for odor stimuli may be higher. We examined the role of Ano2 in ORNs in their native environment in freely breathing mice by imaging activity in ORN axons as they arrive in the olfactory bulb glomeruli. Odor-evoked responses in ORN axons of Ano2-/- animals were consistently larger for a variety of odorants and concentrations. In an open arena, Ano2-/- animals took longer to approach a localized odor source than Ano2+/+ animals, revealing clear olfactory behavioral deficits. Our studies provide the first in vivo evidence toward an alternative or additional role for Ano2 in the olfactory transduction cascade, where it may serve as a feedback mechanism to clamp ORN spike output

Double Perovskites as a Family of Highly Active Catalysts for Oxygen Evolution in Alkaline Solution

The electronic structure of transition metal oxides governs the catalysis of many central reactions for energy storage applications such as oxygen electrocatalysis. Here we exploit the versatility of the perovskite structure to search for oxide catalysts that are both active and stable. We report double perovskites (Ln[subscript 0.5]Ba[subscript 0.5])CoO[subscript 3−δ](Ln=Pr, Sm, Gd and Ho) as a family of highly active catalysts for the oxygen evolution reaction upon water oxidation in alkaline solution. These double perovskites are stable unlike pseudocubic perovskites with comparable activities such as Ba[subscript 0.5]Sr[subscript 0.5]Co[subscript 0.8]Fe[subscript 0.2]O[subscript 3−δ] which readily amorphize during the oxygen evolution reaction. The high activity and stability of these double perovskites can be explained by having the O p-band centre neither too close nor too far from the Fermi level, which is computed from ab initio studies.United States. Department of Energy. Hydrogen Initiative Program (Award DE-FG02-05ER15728)United States. Office of Naval Research (Contract N00014-12-1-0096

Electrode–Electrolyte Interface in Li-Ion Batteries: Current Understanding and New Insights

Understanding reactions at the electrode/electrolyte interface (EEI) is essential to developing strategies to enhance cycle life and safety of lithium batteries. Despite research in the past four decades, there is still limited understanding by what means different components are formed at the EEI and how they influence EEI layer properties. We review findings used to establish the well-known mosaic structure model for the EEI (often referred to as solid electrolyte interphase or SEI) on negative electrodes including lithium, graphite, tin, and silicon. Much less understanding exists for EEI layers for positive electrodes. High-capacity Li-rich layered oxides yLi[subscript 2–x]MnO[subscript 3]·(1–y)Li[subscript 1–x]MO[subscript 2], which can generate highly reactive species toward the electrolyte via oxygen anion redox, highlight the critical need to understand reactions with the electrolyte and EEI layers for advanced positive electrodes. Recent advances in in situ characterization of well-defined electrode surfaces can provide mechanistic insights and strategies to tailor EEI layer composition and properties.BMW GroupMIT/Battelle postdoctoral associate programTaiwan. Ministry of Science and Technology (02-2917-I-564-006-A1)National Defense Science and Engineering Graduate (NDSEG) FellowshipUnited States. Department of Defense (32 CFR 168a DoD)United States. Air Force. Office of Scientific ResearchUnited States. Department of Energy. Office of Science (Contract No. DE-AC02-05CH11231