Virstatin inhibits biofilm formation and motility of Acinetobacter baumannii

BACKGROUND: Acinetobacter baumannii has emerged as an opportunistic nosocomial pathogen causing infections worldwide. One reason for this emergence is due to its natural ability to survive in the hospital environment, which may be explained by its capacity to form biofilms. Cell surface appendages are important determinants of the A. baumannii biofilm formation and as such constitute interesting targets to prevent the development of biofilm-related infections. A chemical agent called virstatin was recently described to impair the virulence of Vibrio cholerae by preventing the expression of its virulence factor, the toxin coregulated pilus (type IV pilus). The objective of this work was to investigate the potential effect of virstatin on A. baumannii biofilms. RESULTS: After a dose-response experiment, we determined that 100 μM virstatin led to an important decrease (38%) of biofilms formed by A. baumannii ATCC17978 grown under static mode. We demonstrated that the production of biofilms grown under dynamic mode was also delayed and reduced. The biofilm susceptibility to virstatin was then tested for 40 clinical and reference A. baumannii strains. 70% of the strains were susceptible to virstatin (with a decrease of 10 to 65%) when biofilms grew in static mode, whereas 60% of strains respond to the treatment when their biofilms grew in dynamic mode. As expected, motility and atomic force microscopy experiments showed that virstatin acts on the A. baumannii pili biogenesis. CONCLUSIONS: By its action on pili biogenesis, virstatin demonstrated a very promising antibiofilm activity affecting more than 70% of the A. baumannii clinical isolates

Application of fluorescently labelled lectins for the study of polysaccharides in biofilms with a focus on biofouling of nanofiltration membranes

The biofilm state is the dominant microbial lifestyle in nature. A biofilm can be defined as cells organised as microcolonies embedded in an organic polymer matrix of microbial origin living at an interface between two different liquids, air and liquid, or solid and liquid. The biofilm matrix is made of extracellular polymeric substances, polysaccharides being considered as the major structural components of the matrix. Fluorescently labelled lectins have been widely used to stain microbial extracellular glycoconjugates in natural and artificial environments, and to study specific bacterial species or highly complex environments. Biofilm development at the membrane surface conducting to biofouling is one of the major problems encountered during drinking water production by filtration. Biofouling affects the durability and effectiveness of filtration membranes. Biofouling can be reduced by pretreatments in order to control two key parameters of water, the bioavailable organic matter concentration and the concentration of live bacteria. Nanofiltration (NF) is a high technology process particularly suited to the treatment of surface waters to produce drinking water that is highly sensitive to biofouling. The development of strategies for fouling prevention and control requires characterizing the fouling material composition and organisation before and after NF membrane cleaning. The aim of this review is to present basics of biofilm analyses after staining with fluorescently labelled lectins and to focus on the use of fluorescent lectins and confocal laser scanning microscopy to analyse NF membrane biofouling

Biochemical Characterization, Molecular Cloning, and Structural Modeling of an Interesting β-1,4-Glucanase from Sclerotinia Sclerotiorum

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Characterization of Membrane Lipidome Changes in Pseudomonas aeruginosa during Biofilm Growth on Glass Wool

International audienceBacteria cells within biofilms are physiologically distinct from their planktonic counterparts. In particular they are more resistant to detrimental environmental conditions. In this study, we monitored the evolution of the phospholipid composition of the inner and outer membranes of P. aeruginosa during the biofilm formation (i.e., from 1-, 2-, to 6-day-old biofilm). Lipidome analyses were performed by electrospray ionization mass spectrometry. In addition to the lipidomic analysis, the fatty acid composition was analysed by gas chromatography/mass spectrometry. We found that the lipidome alterations of the inner and the outer membranes varied with the biofilm age. These alterations in phospholipid compositions reflect a higher diversity in sessile organisms than in planktonic counterparts. The diversity is characterized by the presence o

BacA: a possible regulator that contributes to the biofilm formation of Pseudomonas aeruginosa

Previously, we pointed out in P. aeruginosa PAO1 biofilm cells the accumulation of a hypothetical protein named PA3731 and showed that the deletion of the corresponding gene impacted its biofilm formation capacity. PA3731 belongs to a cluster of 4 genes (pa3732 to pa3729) that we named bac for “Biofilm Associated Cluster.” The present study focuses on the PA14_16140 protein, i.e., the PA3732 (BacA) homolog in the PA14 strain. The role of BacA in rhamnolipid secretion, biofilm formation and virulence, was confirmed by phenotypic experiments with a bacA mutant. Additional investigations allow to advance that the bac system involves in fact 6 genes organized in operon, i.e., bacA to bacF. At a molecular level, quantitative proteomic studies revealed an accumulation of the BAC cognate partners by the bacA sessile mutant, suggesting a negative control of BacA toward the bac operon. Finally, a first crystallographic structure of BacA was obtained revealing a structure homologous to chaperones or/and regulatory proteins

PESQUISAS INTERNACIONAIS RECENTES EM ESTRUTURA DE CAPITAL

Capital Structure is still one of controversial themes in corporate finance, which allows many research activities both on the theories that have been widely discussed but also on the several interrelationships with other corporate aspects. The aim of this article was to review the most recent academic publication of researches involving capital structure of the firms. This study focuses on the last 3 years, from 2011 to 2013, and on the international scientific journals in Finance that present the highest impact factors, namely: The Review of Financial Studies, The Journal of Finance, Journal of Financial Economics e Journal of Banking & Finance. Despite of having been widely discussed, the differences between the main theories on capital structure, the trade-off theory and the pecking order theory, are still object of researches – however, maybe for being the most recent, the theory of equity market timing has been the most discussed theme in the last 3 years. Besides these topics, the researchers have dealt with many aspects of the corporate variables that are direct or indirectly associated with the capital structure decisions. This article presents a brief summary of several publications allowing a general overview on the recent researches.A estrutura de capital ainda é um dos temas controversos em finanças corporativas e ainda propicia muitas pesquisas tanto nas teorias já amplamente discutidas como também nos diversos inter-relacionamentos com outros aspectos corporativos. O objetivo deste artigo foi de fazer uma revisão das publicações recentes que envolvam estudos sobre a estrutura de capital das empresas. A pesquisa foi focada nos últimos 3 anos, de 2011 a 2013, e nas revistas acadêmicas internacionais na área de finanças que apresentam os maiores fatores de impacto, a saber: The Review of Financial Studies, The Journal of Finance, Journal of Financial Economics e Journal of Banking & Finance. Apesar de amplamente discutidas, as diferenças entre as principais teorias sobre a estrutura de capital, a teoria do trade-off e a teoria do pecking order, ainda são pesquisadas – entretanto, talvez por ser mais recente, a teoria do equity market timing é o que mais tem sido analisado nos últimos três anos. Além desses tópicos, os pesquisadores têm tratado de muitos aspectos das variáveis corporativas que direta ou indiretamente estão associados com as decisões de estrutura de capital. Este trabalho apresenta um sumário sucinto das diversas publicações permitindo uma visão geral das pesquisas

Anti-persister activity of squalamine against Acinetobacter baumannii

International audienceSqualamine is a natural polycationic aminosterol extracted from the shark Squalus acanthias. Squalamine displays remarkable efficacy against antimicrobial-resistant Gram-negative and Gram-positive bacteria. Its membranolytic activity and low cytotoxicity make squalamine one of the most promising agents to fight nosocomial pathogens such as Acinetobacter baumannii. In the context of chronic diseases and therapeutic failures associated with this pathogen, the presence of dormant cells, i.e. persisters and viable but non-culturable cells (VBNCs), highly tolerant to antimicrobial compounds is problematic. The aim of this study was to investigate the antibacterial activity of squalamine against this bacterial population of A. baumannii. Bacterial dormancy was induced by cold shock and nutrient starvation in the presence of high doses of either colistin, ciprofloxacin or squalamine. Persisters and VBNCs induced by these treatments were then challenged with 100 mg/L squalamine. The efficacy of each treatment was determined by evaluating culturability on agar medium, membrane integrity (LIVE/DEAD®BacLightTM staining) and respiratory activity (BacLightTM RedoxSensorTM CTC staining) of bacteria. A. baumannii ATCC 17978 generated persisters as well as VBNCs in the presence of high doses of ciprofloxacin but not colistin or squalamine. Squalamine at 100 mg/L (below its haemolytic concentration) was able to kill dormant cells. Squalamine did not induce persister cell or VBNC formation in A. baumannii ATCC 17978. Interestingly, squalamine was significantly active against this type of dormant population generated by ciprofloxacin, making it a very promising anti-persister agent

Glioprotective effect of Ulva rigida extract against UVB cellular damages

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Rapid evolution of pollen and pistil traits as a response to sexual selection in the post-pollination phase of mating

International audienceHighlights d High density promoted greater levels of polyandry among male and female plants d Female plants at high density evolved enlarged stigmas d Male plants at high density evolved faster-growing pollen tubes d Several pollen proteins were upregulated at high density compared with low densit

Mitigation of monocyte driven thrombosis on cobalt chrome surfaces in contact with whole blood by thin film polar/hydrophobic/ionic polyurethane coatings

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