Persistence of experimental Rocio virus infection in the golden hamster (Mesocricetus auratus)

Rocio virus (ROCV) is an encephalitic flavivirus endemic to Brazil. Experimental flavivirus infections have previously demonstrated a persistent infection and, in this study, we investigated the persistence of ROCV infection in golden hamsters (Mesocricetus auratus). The hamsters were infected intraperitoneally with 9.8 LD50/0.02 mL of ROCV and later anaesthetised and sacrificed at various time points over a 120-day period to collect of blood, urine and organ samples. The viral titres were quantified by real-time-polymerase chain reaction (qRT-PCR). The specimens were used to infect Vero cells and ROCV antigens in the cells were detected by immunefluorescence assay. The levels of antibodies were determined by the haemagglutination inhibition technique. A histopathological examination was performed on the tissues by staining with haematoxylin-eosin and detecting viral antigens by immunohistochemistry (IHC). ROCV induced a strong immune response and was pathogenic in hamsters through neuroinvasion. ROCV was recovered from Vero cells exposed to samples from the viscera, brain, blood, serum and urine and was detected by qRT-PCR in the brain, liver and blood for three months after infection. ROCV induced histopathological changes and the expression of viral antigens, which were detected by IHC in the liver, kidney, lung and brain up to four months after infection. These findings show that ROCV is pathogenic to golden hamsters and has the capacity to cause persistent infection in animals after intraperitoneal infection.     

Virioplankton Community Structure in Tunisian Solar Salterns

The microbial community inhabiting Sfax solar salterns on the east coast of Tunisia has been studied by means of different molecular and culture-dependent tools that have unveiled the presence of novel microbial groups as well as a community structure different from that of other coastal hypersaline environments. We have focused on the study of the viral assemblages of these salterns and their changes along the salinity gradient and over time. Viruses from three ponds (C4, M1, and TS) encompassing salinities from moderately hypersaline to saturated (around 14, 19, and 35%, respectively) were sampled in May and October 2009 and analyzed by transmission electron microscopy (TEM) and pulsed-field gel electrophoresis (PFGE). Additionally, for all three October samples and the May TS sample, viral metagenomic DNA was cloned in fosmids, end sequenced, and analyzed. Viral concentration, as well as virus-to-cell ratios, increased along the salinity gradient, with around 10¹⁰ virus-like particles (VLPs)/ml in close-to-saturation ponds, which represents the highest viral concentration reported so far for aquatic systems. Four distinct morphologies could be observed with TEM (spherical, tailed, spindled, and filamentous) but with various proportions in the different samples. Metagenomic analyses indicated that every pond harbored a distinct viral assemblage whose G+C content could be roughly correlated with that of the active part of the microbial community that may have constituted the putative hosts. As previously reported for hypersaline metaviromes, most sequences did not have matches in the databases, although some were conserved among the Sfax metaviromes. BLASTx, BLASTp, and dinucleotide frequency analyses indicated that (i) factors additional to salinity could be structuring viral communities and (ii) every metavirome had unique gene contents and dinucleotide frequencies. Comparison with hypersaline metaviromes available in the databases indicated that the viral assemblages present in close-to-saturation environments located thousands of kilometers apart presented some common traits among them in spite of their differences regarding the putative hosts. A small core metavirome for close-to-saturation systems was found that contained 7 sequences of around 100 nucleotides (nt) whose function was not hinted at by in silico search results, although it most likely represents properties essential for hyperhalophilic viruses.     

High-yield secretion of multiple client proteins in Aspergillus

Production of pure and high-yield client proteins is an important technology that addresses the need for industrial applications of enzymes as well as scientific experiments in protein chemistry and crystallization. Fungi are utilized in industrial protein production because of their ability to secrete large quantities of proteins. In this study, we engineered a high-expression-secretion vector, pEXPYR that directs proteins towards the extracellular medium in two Aspergillii host strains, examine the effect of maltose-induced over-expression and protein secretion as well as time and pH-dependent protein stability in the medium. We describe five client proteins representing a core set of hemicellulose degrading enzymes that accumulated up to 50-100 mg/L of protein. Using a recyclable genetic marker that allows serial insertion of multiple genes, simultaneous hyper-secretion of three client proteins in a single host strain was accomplished.     

Genome sequence of the bacteriocin-producing Lactobacillus curvatus strain CRL705

Lactobacillus curvatus is one of the most prevalent lactic acid bacteria found in fermented meat products. Here, we present the draft genome sequence of Lactobacillus curvatus CRL705, a bacteriocin producer strain isolated from an Argentinean artisanal fermented sausage, which consists of 1,833,251 bp (GC content, 41.9%) and two circular plasmids of 12,342 bp (pRC12; GC, 43.9%) and 18,664 bp (pRC18; GC, 34.4%).     

Invasion and initial replication of ultraviolet irradiated waterborne infective stages of Myxobolus cerebralis results in immunity to whirling disease in rainbow trout

Myxobolus cerebralis is a microscopic metazoan parasite (Phylum Myxozoa: Myxosporea) associated with salmonid whirling disease. There are currently no vaccines to minimise the serious negative economical and ecological impacts of whirling disease among populations of salmonid fish worldwide. UV irradiation has been shown to effectively inactivate the waterborne infective stages or triactinomyxons of M. cerbralis in experimental and hatchery settings but the mechanisms by which the parasite is compromised are unknown. Treatments of triactinomyxons with UV irradiation at doses from 10 to 80 mJ/cm(2) either prevented (20-80 mJ/cm(2)) or significantly inhibited (10 mJ/cm(2)) completion of the parasite life cycle in experimentally exposed juvenile rainbow trout (Oncorhynchus mykiss). However, even the highest doses of UV irradiation examined (80 mJ/cm(2)) did not prevent key steps in the initiation of parasite infection, including attachment and penetration of the epidermis of juvenile rainbow trout as demonstrated by scanning electron and light microscopy. Furthermore, replication of UV-treated parasites within the first 24h following invasion of the caudal fin was suggested by the detection of concentrations of parasite DNA by quantitative PCR comparable to that among fish exposed to an equal concentration of untreated triactinomyxons. Subsequent development of parasites treated with an 80 mJ/cm(2) dose of UV irradiation however, was impaired as demonstrated by the decline and then lack of detection of parasite DNA; a trend beginning at 10 days and continuing thereafter until the end of the study at 46 days post parasite exposure. Treatments of triactinomyxons with a lower dose of UV irradiation (20 mJ/cm(2)) resulted in a more prolonged survival with parasite DNA detected, although at very low concentrations, in fish up to 49 days post parasite exposure. The successful invasion but only short-term survival of parasites treated with UV in rainbow trout resulted in a protective response to challenges with fully infective triactinomyxons. Prior treatments of juvenile rainbow trout with UV-treated triactinomyxons (10 and 20 mJ/cm(2)) resulted in a reduced prevalence of infection and significantly lower concentrations of cranial myxospores (two direct measures of the severity of whirling disease) compared with trout receiving no prior treatments when assessed 5 months post parasite exposure to fully infective triactinomyxons.     

Altering the interfacial activation mechanism of a lipase by solid-phase selective chemical modification

This study presents a combined protein immobilization, directed mutagenesis, and site-selective chemical modification approach, which was used to create a hyperactivated semisynthetic variant of BTL2. Various alkane chains were tethered at three different positions in order to mimic the lipase interfacial activation exogenously triggered by detergents. Optimum results were obtained when a dodecane chain was introduced at position 320 by solid-phase site-selective chemical modification. The resulting semisynthetic variant showed a 2.5-fold higher activity than the wild-type nonmodified variant in aqueous conditions. Remarkably, this is the maximum hyperactivation ever observed for BTL2 in the presence of detergents such as Triton X-100. We present evidence to suggest that the endogenous dodecane chain hyperactivates the enzyme in a similar fashion as an exogenous detergent molecule. In this way, we also observe a faster irreversible enzyme inhibition and an altered detergent sensitivity profile promoted by the site-selective chemical modification. These findings are also supported by fluorescence studies, which reveal that the structural conformation changes of the semisynthetic variant are different to those of the wild type, an effect that is more pronounced in the presence of detergent. Finally, the optimal immobilized semisynthetic variant was successfully applied to the selective synthesis of oxiran-2-yl butyrate. Significantly, this biocatalyst is 12-fold more efficient than the immobilized wild-type enzyme, producing the S-enantiomer with higher enantiospecificity (ee = 92%).     

Effects of point substitutions on the structure of toxic Alzheimer's β-amyloid channels: atomic force microscopy and molecular dynamics simulations

Alzheimer's disease (AD) is a misfolded protein disease characterized by the accumulation of β-amyloid (Aβ) peptide as senile plaques, progressive neurodegeneration, and memory loss. Recent evidence suggests that AD pathology is linked to the destabilization of cellular ionic homeostasis mediated by toxic pores made of Aβ peptides. Understanding the exact nature by which these pores conduct electrical and molecular signals could aid in identifying potential therapeutic targets for the prevention and treatment of AD. Here using atomic force microscopy (AFM) and molecular dynamics (MD) simulations, we compared the imaged pore structures with models to predict channel conformations as a function of amino acid sequence. Site-specific amino acid (AA) substitutions in the wild-type Aβ(1-42) peptide yield information regarding the location and significance of individual AA residues to its characteristic structure-activity relationship. We selected two AAs that our MD simulation predicted to inhibit or permit pore conductance. The substitution of Phe19 with Pro has previously been shown to eliminate conductance in the planar lipid bilayer system. Our MD simulations predict a channel-like shape with a collapsed pore, which is supported by the AFM channel images. We suggest that proline, a known β-sheet breaker, creates a kink in the center of the pore and prevents conductance via blockage. This residue may be a viable target for drug development studies aiming to inhibit Aβ from inducing ionic destabilization toxicity. The substitution of Phe20 with Cys exhibits pore structures indistinguishable from the wild type in AFM images. MD simulations predict site 20 to face the solvated pore. Overall, the mutations support the previously predicted β-sheet-based channel structure.     

Isolation and characterization of 10 microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean relict plant

? Premise of the study: The main aim of this study was to isolate and characterize microsatellite loci in Cneorum tricoccon (Cneoraceae), a Mediterranean shrub relict of the early Tertiary, which inhabits western Mediterranean islands and coasts. Microsatellites will be useful for investigating biogeography and landscape genetics across the species distribution range, including current or past gene flow. ? Methods and Results: Seventeen microsatellite loci were characterized, of which 10 were polymorphic and amplified for a total of 56 alleles in three populations of C. tricoccon. The markers revealed average coefficients of expected heterozygosity (H(e) = 0.425), observed heterozygosity (H(o) = 0.282), and inbreeding coefficient value per population (F(IS) = 0.408). ? Conclusions: These microsatellite primers will potentially be useful in the study of population and landscape genetics, conservation status of isolated populations, island-continental distribution, current or historical movements between populations, and in the investigation of the consequences of dispersal mechanisms of these plants.     

Galactosylated Fucose Epitopes in Nematodes: INCREASED EXPRESSION IN A CAENORHABDITIS MUTANT ASSOCIATED WITH ALTERED LECTIN SENSITIVITY AND OCCURRENCE IN PARASITIC SPECIES

The modification of α1,6-linked fucose residues attached to the proximal (reducing-terminal) core N-acetylglucosamine residue of N-glycans by β1,4-linked galactose ("GalFuc" epitope) is a feature of a number of invertebrate species including the model nematode Caenorhabditis elegans. A pre-requisite for both core α1,6-fucosylation and β1,4-galactosylation is the presence of a nonreducing terminal N-acetylglucosamine; however, this residue is normally absent from the final glycan structure in invertebrates due to the action of specific hexosaminidases. Previously, we have identified two hexosaminidases (HEX-2 and HEX-3) in C. elegans, which process N-glycans. In the present study, we have prepared a hex-2;hex-3 double mutant, which possesses a radically altered N-glycomic profile. Whereas in the double mutant core α1,3-fucosylation of the proximal N-acetylglucosamine was abolished, the degree of galactosylation of core α1,6-fucose increased, and a novel Galα1,2Fucα1,3 moiety attached to the distal core N-acetylglucosamine residue was detected. Both galactosylated fucose moieties were also found in two parasitic nematodes, Ascaris suum and Oesophagostomum dentatum. As core modifications of N-glycans are known targets for fungal nematotoxic lectins, the sensitivity of the C. elegans double hexosaminidase mutant was assessed. Although this mutant displayed hypersensitivity to the GalFuc-binding lectin CGL2 and the N-acetylglucosamine-binding lectin XCL, the mutant was resistant to CCL2, which binds core α1,3-fucose. Thus, the use of C. elegans mutants aids the identification of novel N-glycan modifications and the definition of in vivo specificities of nematotoxic lectins with potential as anthelmintic agents.