Physico-chemical and hygienic property modifications of stainless steel surfaces induced by conditioning with food and detergent

The effect of repeated conditioning procedures (25 runs), consisting of soiling (milk and meat products) and cleaning steps, on the hygienic status, physico-chemical properties and surface chemical composition of stainless steel (SS) surfaces, was investigated. Five SSs differing in grade and finish were used. Both soiling and surface cleaning/conditioning procedures resulted in a similar increase in the surface contamination with carbon, while the changes in the basic component of the surface free energy depended on the conditioning procedure. The passive film was also affected, the Fe/Cr ratio in particular. The hygienic status was also changed, especially with milk as shown by monitoring the number of residual adhering Bacillus cereus spores after contaminating the surface with spores followed by cleaning. The results show that in food environments, the presence and the nature of conditioning molecules play a major role in the hygienic status of SS surfaces.     

Zinc accumulation patterns in four Anthyllis vulneraria subspecies supplemented with mineral nitrogen or grown in the presence of their symbiotic bacteria

Aims

This work examines Zn accumulation in four Anthyllis vulneraria subspecies supplemented with mineral nitrogen or grown in the presence of their symbiotic bacteria.

Methods

Anthyllis vulneraria subspecies were grown hydroponically in the presence of high levels of ZnSO₄. The plants were either grown in symbiosis with one of two non-metallicolous or metallicolous Mesorhizobium inoculants or in the presence of KNO₃.

Results

When exposed to 1,000 μM Zn, shoot and root biomass of three out of our four Anthyllis subspecies cultivated with NO₃ dropped significantly by about 24–28 %; carpatica, the fourth subspecies, was not affected. Subspecies carpatica Zn tolerance was confirmed when in symbiosis with the metallicolous strain. In the presence of 1,000 μM Zn, the different Anthyllis subspecies concentrated more Zn in their roots than in their shoots and only subsp. carpatica accumulated a significant amount of Zn in its shoots. The most remarkable feature was the drastic decrease in Zn concentration in both roots (up to 2.5–3 fold) and shoots (2.6-fold) of subsp. carpatica exposed to 1,000 μM Zn and nodulated whatever the Mesorhizobium strain used, compared to the N-grown plants.

Conclusions

Our results bring new perspectives as regards phytostabilization, with the potential use of a rhizobium-inoculated leguminous subspecies displaying unusual Zn tolerance.     

Identification of Alpha Interferon-Induced Envelope Mutations of Hepatitis C Virus In Vitro Associated with Increased Viral Fitness and Interferon Resistance

Alpha interferon (IFN-α) is an essential component of innate antiviral immunity and of treatment regimens for chronic hepatitis C virus (HCV) infection. Resistance to IFN might be important for HCV persistence and failure of IFN-based therapies. Evidence for HCV genetic correlates of IFN resistance is limited. Experimental studies were hampered by lack of HCV culture systems. Using genotype (strain) 1a(H77) and 3a(S52) Core-NS2 JFH1-based recombinants, we aimed at identifying viral correlates of IFN-α resistance in vitro. Long-term culture with IFN-α2b in Huh7.5 cells resulted in viral spread with acquisition of putative escape mutations in HCV structural and nonstructural proteins. Reverse genetic studies showed that primarily amino acid changes I348T in 1a(H77) E1 and F345V/V414A in 3a(S52) E1/E2 increased viral fitness. Single-cycle assays revealed that I348T and F345V/V414A enhanced viral entry and release, respectively. In assays allowing viral spread, these mutations conferred a level of IFN-α resistance exceeding the observed fitness effect. The identified mutations acted in a subtype-specific manner but were not found in genotype 1a and 3a patients, who failed IFN-α therapy. Studies with HCV recombinants with different degrees of culture adaptation confirmed the correlation between viral fitness and IFN-α resistance. In conclusion, in vitro escape experiments led to identification of HCV envelope mutations resulting in increased viral fitness and conferring IFN-α resistance. While we established a close link between viral fitness and IFN-α resistance, identified mutations acted via different mechanisms and appeared to be relatively specific to the infecting virus, possibly explaining difficulties in identifying signature mutations for IFN resistance.     

A Model of the Membrane-bound Cytochrome b5-Cytochrome P450 Complex from NMR and Mutagenesis Data

Microsomal cytochrome b₅ (cytb₅) is a membrane-bound protein that modulates the catalytic activity of its redox partner, cytochrome P4502B4 (cytP450). Here, we report the first structure of full-length rabbit ferric microsomal cytb₅ (16 kDa), incorporated in two different membrane mimetics (detergent micelles and lipid bicelles). Differential line broadening of the cytb₅ NMR resonances and site-directed mutagenesis data were used to characterize the cytb₅ interaction epitope recognized by ferric microsomal cytP450 (56 kDa). Subsequently, a data-driven docking algorithm, HADDOCK (high ambiguity driven biomolecular docking), was used to generate the structure of the complex between cytP4502B4 and cytb₅ using experimentally derived restraints from NMR, mutagenesis, and the double mutant cycle data obtained on the full-length proteins. Our docking and experimental results point to the formation of a dynamic electron transfer complex between the acidic convex surface of cytb₅ and the concave basic proximal surface of cytP4502B4. The majority of the binding energy for the complex is provided by interactions between residues on the C-helix and β-bulge of cytP450 and residues at the end of helix α4 of cytb₅. The structure of the complex allows us to propose an interprotein electron transfer pathway involving the highly conserved Arg-125 on cytP450 serving as a salt bridge between the heme propionates of cytP450 and cytb₅. We have also shown that the addition of a substrate to cytP450 likely strengthens the cytb₅-cytP450 interaction. This study paves the way to obtaining valuable structural, functional, and dynamic information on membrane-bound complexes.     

Is the caste-ratio of the oligolectic bumblebee Bombus gerstaeckeri Morawitz (Hymenoptera: Apidae) biased to queens?

Three bumblebee species, foraging on Aconitum spp. have been commonly observed in Eyne (France, East Pyrénées): Bombus gerstaeckeri, B. hortorum and B. wurflenii. We estimated the population of these three species. For B. hortorum and B. wurflenii, the total workers populations foraging on Aconitum spp. ranged from 101 to 523 and 156 to 270, respectively. These two species also forage on other plants while B. gerstaeckeri visits only Aconitum spp. The population of B. gerstaeckeri observed was extremely small, founded by 33 queens only in 2001. With a total number of workers estimated from 40 to 102, the observed workers/queens ratio, 1 to 3 workers for each queen, is very unusual for a eusocial species. Also we observed queens foraging during the whole life of the colony. This kind of social organisation is similar to that of some high arctic species. It could be interpreted as the result of an insularity syndrome.     

Révision des Xylocopinae (Hymenoptera : Apidae) de France et de Belgique

Cette publication présente les résultats d’une étude de 6.263 spécimens de Xylocopinae récoltés en France métropolitaine (France continentale et Corse) et en Belgique et qui proviennent de récoltes personnelles et de 63 institutions et collections privées. Les Xylocopinae de France sont représentées par 11 espèces du genre Ceratina et 4 espèces du genre Xylocopa. Seules deux de ces espèces sont présentes en Belgique : Xylocopa violacea (L.) et Ceratina cyanea (Kirby). Un nouveau sous-genre pour le genre Ceratina est décrit : Dalyatina n. subg. Il comporte l’espèce méditerranéenne Ceratina parvula Smith présente en France, ainsi que six autres espèces d’Afrique subsaharienne. Pour chaque genre, sous-genre et espèce, les auteurs fournissent une diagnose, une diagnose différentielle, la liste des fleurs visitées, la liste des sites de nidification, la carte de distribution en France métropolitaine, un diagramme phénologique et une clé d’identifi cation des genres, sous-genres et espèces. La systématique, la biogéographie, l’écologie et le sexe ratio des espèces sont présentés et discutés. Les Xylocopinae apparaissent comme très largement polylectiques mais montrent une très nette affinité envers les Lamiaceae, les Asteraceae Cardueae et, pour le genre Xylocopa, envers les Fabaceae. Toutes les espèces présentent une phénologie estivale qui s’étend d’avril à septembre. Le sexe-ratio de la plupart des espèces est biaisé vers les femelles. Aucun mâle de C. parvula, pour 120 femelles, n’a été observé ce qui suggère que, en France du moins, l’espèce pourrait se reproduire par parthénogenèse thélytoque comme c’est le cas de C. dallatorreana Friese. La publication comprend 62 dessins au trait, 18 photos au microscope électronique à balayage, 17 cartes, 14 graphiques de phénologie, une liste de 232 espèces de fleurs visitées par les Xylocopinae, dont 176 observations originales, et 171 références.     

Ribosomal proteins as biomarkers for bacterial identification by mass spectrometry in the clinical microbiology laboratory

Whole-cell matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) is a rapid method for identification of microorganisms that is increasingly used in microbiology laboratories. This identification is based on the comparison of the tested isolate mass spectrum with reference databases. Using Neisseria meningitidis as a model organism, we showed that in one of the available databases, the Andromas database, 10 of the 13 species-specific biomarkers correspond to ribosomal proteins. Remarkably, one biomarker, ribosomal protein L32, was subject to inter-strain variability. The analysis of the ribosomal protein patterns of 100 isolates for which whole genome sequences were available, confirmed the presence of inter-strain variability in the molecular weight of 29 ribosomal proteins, thus establishing a correlation between the sequence type (ST) and/or clonal complex (CC) of each strain and its ribosomal protein pattern. Since the molecular weight of three of the variable ribosomal proteins (L30, L31 and L32) was included in the spectral window observed by MALDI-TOF MS in clinical microbiology, i.e., 3640–12000 m/z, we were able by analyzing the molecular weight of these three ribosomal proteins to classify each strain in one of six subgroups, each of these subgroups corresponding to specific STs and/or CCs. Their detection by MALDI-TOF allows therefore a quick typing of N. meningitidis isolates.