Towards eco-friendly biocides: preparation, antibiofilm activity of hemibastadin analogues.

The antibiofilm activity of three hemibastadins analogues was evaluated against different marine bacterial strains through mono-species biofilms and through a multi-species model of biofilm. Results showed that compound 3 exhibited interesting antibiofilm efficiencies effective concentrations (EC50 ) in the range of 30-100 µmol l-1 without acute toxicity against bacteria. Toxicity against nontargeted organisms was also considered showing that the compound did not affect the global bacterial community at a concentration of 75-100 µmol l-1 . These results provided baseline data concerning the toxicity of antibiofilm biocides against marine organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports relevant information about antibiofilm activity of original derivatives of hemibastadin alkaloids. The most active compound was shown to act as a specific anti-biofilm inhibitor without affecting viability of the targeted bacteria no more than those of the global bacterial community of a seawater sample. Taken together, these findings indicate the potentiality of such compounds to be used as original nonbiocidal molecules for designing eco-friendly antifouling solutions.

[Systemic microsporidiosis and toxoplasmosis in a patient with T prolymphocytic leukemia]. / Microsporidiose et toxoplasmose disséminées chez une patiente présentant une leucémie prolymphocytaire T.

We report a case of microsporidiosis in a 72-year-old woman presenting with prolymphocytic leukemia. The underlying conditions 7 months after leukemia was diagnosed were pancytopenia and immunosuppression due to alemtuzumab and pentostatin. The patient's status had worsened and she presented with dysuria. Urine cultures for bacteria were repeatedly negative. She was first empirically treated with broad-spectrum antibiotics. Three months later, urinary symptoms were persisting. Her blood lymphocyte count was 90/microl. Urine examination was positive for microsporidia using modified trichrome staining and Uvitex 2B fluorescence. Microsporidia were also detected in stools. The patient was cured by albendazole. This was consistent with an infection due to Encephalitozoon sp. Concurrently, disseminated toxoplasmosis was diagnosed. Toxoplasma gondii was detected in bone marrow, broncho-alveolar lavage and cerebrospinal fluid. She was successfully treated with sulfadiazine-pyrimethamine. Four cases of microsporidiosis in myeloid leukemic patients have been already described. The present case in a patient with lymphoid leukemia is the first to be reported.

Thermodynamically consistent picture of the phase-field model of vesicles: elimination of the surface tension.

In two recent papers [D. Jamet and C. Misbah, Phys. Rev. E 76, 051907 (2007); 78, 031902 (2008)], we considered a thermodynamically consistent model for vesicles and membranes, where we dealt, in the first paper, with the membrane local incompressibility condition, while in the second one with the bending energy and the derivation of a constitutive law of the composite fluid: ambient fluid+membrane . This is the last paper of this series and focuses on the elimination of surface tension (inherent in phase-field models), retaining the thermodynamically consistent model. We write down the complete set of equations and the full constitutive law for membranes embedded in a Newtonian fluid.

Toward a thermodynamically consistent picture of the phase-field model of vesicles: curvature energy.

We extend our recent work on phase-field model for vesicles [D. Jamet and C. Misbah, Phys. Rev. E 76, 051907 (2007)]-where only the membrane local incompressibility was treated-to the situation where the bending forces and spontaneous curvature are included. We show how the general phase-field equations can be derived within a thermodynamic consistent picture. We analyze a general form of the bending energy, where the Helfrich bending force is treated as a special case. The dynamical evolution equation derived here for the velocity field allows one to write down a constitutive law of the composite fluid: The ambient fluid plus the membrane. This constitutive law has a viscoelastic form, the viscous part arises from the fluid, while the elastic one represents the action of the membrane. It is shown that the elastic stress tensor is not symmetric, owing to bending torque, inherent to a diffuse membrane model.

Towards a thermodynamically consistent picture of the phase-field model of vesicles: local membrane incompressibility.

A phase-field model for vesicles including hydrodynamics was presented in two and three dimensions [T. Biben and C. Misbah, Phys. Rev. E 67, 031908 (2003); T. Biben, K. Kassner, and C. Misbah, Phys. Rev. E 72, 041921 (2005)]. A particularly important feature for vesicles is that their membrane is locally incompressible. In these works a tension field defined everywhere in the bulk was introduced in order to fulfill local membrane inextensibility. Here we reconsider the original model by treating the phase field as a thermodynamic variable and develop a picture which is consistent with the second law of thermodynamics. This enables us to write the phase-field evolution equations in terms of a thermodynamical potential. This potential acquires, at global equilibrium, a Lyapunov functional character. The goal of this paper is twofold: (i) The first and primary goal is purely conceptual, in that we can write down a first and second principle for membranes, from which the evolution equations follow, thanks to the evaluation of the entropy production and the use of concepts of irreversible thermodynamics. (ii) Due to the monotonous character of the evolution of the functional (at global equilibrium), we expect this formulation to be more appropriate for numerical studies. The formalism developed to account for the local incompressibility of the membrane is believed to offer a systematic framework in order to include naturally other physical ingredients, as briefly discussed here and demonstrated in future works.

Size-fractionated alkaline phosphatase activity in the hypereutrophic Villerest reservoir (Roanne, France).

Seasonal changes in size-fractionated alkaline phosphatase activity (APA) were studied in the hypereutrophic Villerest reservoir (Roanne, France) to determine whether the APA showed seasonal variations coupled to abiotic and biotic variables. Samples were collected at different depths from November 1992 to October 1993. The phosphatase activities were measured spectrophotometrically with pnitrophenyl phosphate as the substrate and related to protein concentrations. No correlations were found between APA and soluble reactive phosphorus concentrations during an annual cycle. Free phosphatases were particularly high in the epilimnion (54.5% of total activity was at 5 m) and decreased with depth (4% of total APA at 40 m). The contribution of small microorganisms to APA increased with depth. It was concluded that APA is not a valid quantitative test of the phosphorus status of aquatic microorganisms.