Cryptosporidium parvum (Eucoccidiorida: Cryptosporiidae) in calves: results of a longitudinal study in a dairy farm in Sfax, Tunisia

A longitudinal study was undertaken to determine the prevalence of Cryptosporidium in a dairy farm in Sfax, Tunisia. 480 faecal samples were obtained from 30 calves under one month of age. All faecal samples were analysed for Cryptosporidium oocysts by microscopic examination of smears stained by modified Ziehl Neelsen technique. The parasite was detected in 26 calves (86.7%). Infection was significantly associated with diarrhoea. A molecular characterization, performed in seven calves, confirmed that isolates were C. parvum. This work is the first report on Cryptosporidium in calves in Tunisia.     

Characterization of lactobacilli isolated from caper berry fermentations

AIMS: To determine the metabolic and functional properties of lactobacilli isolated from caper fermentation. METHODS AND RESULTS: A collection of 58 lactobacilli from fermentation of caper berries (including species of Lactobacillus plantarum, Lactobacillus paraplantarum, Lactobacillus pentosus, Lactobacillus brevis and Lactobacillus fermentum) was studied. Strains were classified in different clusters according to sugar fermentation patterns. Most strains of L. plantarum (the predominant species in the fermentation) clustered in a single group. Analysis of enzymatic activities revealed a high incidence of leucine aminopeptidase, acid phosphatase, beta-galactosidase and beta-glucosidase among the different strains of lactobacilli. A high number of strains were able to degrade raffinose and stachyose. Phytase activity and bile salt hydrolase activity were only detected in certain strains of L. plantarum. CONCLUSIONS: Lactobacilli from caper fermentation are metabolically diverse, and some strains display functional properties of interest. SIGNIFICANCE AND IMPACT OF THE STUDY: Strains of lactobacilli with selected functional properties could be good candidates for future development of commercial starters for industrial caper fermentation.     

Adaptation of acidogenic sludge to increasing glycerol concentrations for biohydrogen production

Hydrogen is a promising alternative as an energetic carrier and its production by dark fermentation from wastewater has been recently proposed, with special attention to crude glycerol as potential substrate. In this study, two different feeding strategies were evaluated for replacing the glucose substrate by glycerol substrate: a one-step strategy (glucose was replaced abruptly by glycerol) and a step-by-step strategy (progressive decrease of glucose concentration and increase of glycerol concentration from 0 to 5 g L^?1), in a continuous stirred tank reactor (12 h of hydraulic retention time (HRT), pH 5.5, 35 °C). While the one-step strategy led to biomass washout and unsuccessful H₂ production, the step-by-step strategy was efficient for biomass adaptation, reaching acceptable hydrogen yields (0.4?±?0.1 mol_H2?mol^?1 _{glycerol consumed}) around 33 % of the theoretical yield independently of the glycerol concentration. Microbial community structure was investigated by single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) fingerprinting techniques, targeting either the total community (16S ribosomal RNA (rRNA) gene) or the functional Clostridium population involved in H₂ production (hydA gene), as well as by 454 pyrosequencing of the total community. Multivariate analysis of fingerprinting and pyrosequencing results revealed the influence of the feeding strategy on the bacterial community structure and suggested the progressive structural adaptation of the community to increasing glycerol concentrations, through the emergence and selection of specific species, highly correlated to environmental parameters. Particularly, this work highlighted an interesting shift of dominant community members (putatively responsible of hydrogen production in the continuous stirred tank reactor (CSTR)) according to the gradient of glycerol proportion in the feed, from the family Veillonellaceae to the genera Prevotella and Clostridium sp., putatively responsible of hydrogen production in the CSTR.     

Patterns of Sequence Divergence and Evolution of the S1 Orthologous Regions between Asian and African Cultivated Rice Species

A strong postzygotic reproductive barrier separates the recently diverged Asian and African cultivated rice species, Oryza sativa and O. glaberrima. Recently a model of genetic incompatibilities between three adjacent loci: S₁A, S₁ and S₁B (called together the S₁ regions) interacting epistatically, was postulated to cause the allelic elimination of female gametes in interspecific hybrids. Two candidate factors for the S₁ locus (including a putative F-box gene) were proposed, but candidates for S₁A and S₁B remained undetermined. Here, to better understand the basis of the evolution of regions involved in reproductive isolation, we studied the genic and structural changes accumulated in the S₁ regions between orthologous sequences. First, we established an 813 kb genomic sequence in O. glaberrima, covering completely the S₁A, S₁ and the majority of the S₁B regions, and compared it with the orthologous regions of O. sativa. An overall strong structural conservation was observed, with the exception of three isolated regions of disturbed collinearity: (1) a local invasion of transposable elements around a putative F-box gene within S₁, (2) the multiple duplication and subsequent divergence of the same F-box gene within S₁A, (3) an interspecific chromosomal inversion in S₁B, which restricts recombination in our O. sativa×O. glaberrima crosses. Beside these few structural variations, a uniform conservative pattern of coding sequence divergence was found all along the S₁ regions. Hence, the S₁ regions have undergone no drastic variation in their recent divergence and evolution between O. sativa and O. glaberrima, suggesting that a small accumulation of genic changes, following a Bateson-Dobzhansky-Muller (BDM) model, might be involved in the establishment of the sterility barrier. In this context, genetic incompatibilities involving the duplicated F-box genes as putative candidates, and a possible strengthening step involving the chromosomal inversion might participate to the reproductive barrier between Asian and African rice species.     

Immune risk phenotype is associated with nosocomial lung infections in elderly in-patients

Background

Nosocomial infections are extremely common in the elderly and may be related to ageing of the immune system. The Immune Risk Phenotype (IRP), which predicts shorter survival in elderly patients, has not been evaluated as a possible risk factor for nosocomial infection. Our aim was to assess the prevalence of nosocomial infections in elderly in-patients and to investigate potential relationships between nosocomial infections and the immunophenotype, including IRP parameters.

Results

We included 252 consecutive in-patients aged 70 years or over (mean age, 85 ± 6.2 years), between 2006 and 2008. Among them, 97 experienced nosocomial infections, yielding a prevalence rate of 38.5% (95% confidence interval, 32.5-44.5). The main infection sites were the respiratory tract (21%) and urinary tract (17.1%) When we compared immunological parameters including cell counts determined by flow cytometry in the groups with and without nosocomial infections, we found that the group with nosocomial infections had significantly lower values for the CD4/CD8 ratio and naive CD8 and CD4 T-cell counts and higher counts of memory CD8 T-cells with a significant increase in CD28-negative CD8-T cells. Neither cytomegalovirus status (positive in 193/246 patients) nor presence of the IRP was associated with nosocomial infections. However, nosocomial pneumonia was significantly more common among IRP-positive patients than IRP-negative patients (17/60 versus 28/180; p = 0.036).

Conclusion

Immunological parameters that are easy to determine in everyday practice and known to be associated with immune system ageing and shorter survival in the elderly are also associated with an elevated risk of nosocomial pneumonia in the relatively short term.     

Cr(VI) detoxification by Desulfovibrio vulgaris strain Hildenborough: microbe–metal interactions studies

Toxic heavy metals constitute a worldwide environmental pollution problem. Bioremediation technologies represent efficient alternatives to the classic cleaning-up of contaminated soil and ground water. Most toxic heavy metals such as chromium are less soluble and toxic when reduced than when oxidized. Sulfate-reducing bacteria (SRB) are able to reduce heavy metals by a chemical reduction via the production of H₂S and by a direct enzymatic process involving hydrogenases and c₃ cytochromes. We have previously reported the effects of chromate [Cr(VI)] on SRB bioenergetic metabolism and the molecular mechanism of the metal reduction by polyhemic cytochromes. In the current work, we pinpoint the bacteria–metal interactions using Desulfovibrio vulgaris strain Hildenborough as a model. The bacteria were grown in the presence of high Cr(VI) concentration, where they accumulated precipitates of a reduced form of chromium, trivalent chromium [Cr(III)], on their cell surfaces. Moreover, the inner and outer membranes exhibited precipitates that shared the spectroscopic signature of trivalent chromium. This subcellular localization is consistent with enzymatic metal reduction by cytochromes and hydrogenases. Regarding environmental significance, our findings point out the Cr(VI) immobilization mechanisms of SRB; suggesting that SRB are highly important in metal biogeochemistry.     

Increased xerotolerance of Saccharomyces cerevisiae during an osmotic pressure ramp over several generations

Although mechanisms involved in response of Saccharomyces cerevisiae to osmotic challenge are well described for low and sudden stresses, little is known about how cells respond to a gradual increase of the osmotic pressure (reduced water activity; a_w) over several generations as it could encounter during drying in nature or in food processes. Using glycerol as a stressor, we propagated S. cerevisiae through a ramp of the osmotic pressure (up to high molar concentrations to achieve testing-to-destruction) at the rate of 1.5 MPa day^-1 from 1.38 to 58.5 MPa (0.990–0.635 a_w). Cultivability (measured at 1.38 MPa and at the harvest osmotic pressure) and glucose consumption compared with the corresponding sudden stress showed that yeasts were able to grow until about 10.5 MPa (0.926 a_w) and to survive until about 58.5 MPa, whereas glucose consumption occurred until 13.5 MPa (about 0.915 a_w). Nevertheless, the ramp conferred an advantage since yeasts harvested at 10.5 and 34.5 MPa (0.778 a_w) showed a greater cultivability than glycerol-shocked cells after a subsequent shock at 200 MPa (0.234 a_w) for 2 days. FTIR analysis revealed structural changes in wall and proteins in the range 1.38–10.5 MPa, which would be likely to be involved in the resistance at extreme osmotic pressure.     

Topical glucose and accumulation of excitotoxic and other amino acids in ischemic cerebral cortex.

Pre-ischemic hyperglycemia aggravates brain damage due to transient global ischemia as demonstrated by exacerbation of brain lesions. Lactacidosis and elevated glutamate levels have been implicated as mechanisms of the increased damage. Our objective was to determine the effects of different levels of glucose (0, 66.5, 450 mg/dL) in cortical superfusates on the ischemia/reperfusion-evoked release of amino acids from the rat cerebral cortex. Physiologic levels of glucose significantly reduced the amount of aspartate, glutamate and gamma-aminobutyric acid and the supra-physiologic levels of glucose reduced the amount of aspartate and phosphoethanolamine released from the cortex during ischemia/reperfusion in comparison with no glucose. The decrease in glutamate release may be due to increased availability of glucose for glycolysis with the subsequent formation of ATP and lactate, which has been shown to act as an energy source for neurons. The decreased levels may also reflect the continued energy-dependent uptake of glutamate by glial cells.     

Non-covalent interaction between procyanidins and apple cell wall material: Part I. Effect of some environmental parameters

The adsorption of procyanidins on cell wall material were quantified by bringing into contact a solution of procyanidins and a suspension of cell wall material. The influence of structural features such as degree of polymerisation (DP) and percentage of galloylation (% gall), and of physico-chemical parameters such as pH, ionic strength, temperature and presence of ethanol were investigated. The amount of procyanidins bound to the cell wall increased with the DP, the % gall, and the proportion of (+)-catechin, the last indicating an effect of the stereochemistry of the flavan-3-ols. Complex formation between procyanidins and cell wall material was not affected by pH in the range 2.2-7 but it was decreased by urea, dioxane and ethanol. Adsorption increased with increasing ionic strength and decreased with increasing temperature. This indicated that the bonds which governed the interaction between procyanidins and cell wall material were weak energy bonds of the type hydrogen bond and hydrophobic interaction.     

Short synthesis of 16beta-hydroxy-5alpha-cholestane-3,6-dione a novel cytotoxic marine oxysterol

The first and short synthesis of 16beta-hydroxy-5alpha-cholestane-3,6-dione 1 a metabolite from marine algae, has been achieved in six steps from readily available diosgenin 5. Selective deoxygenation of primary alcohol of triol 6 has been accomplished in one step using Et(3)SiH and catalytic amount of B(C(6)F(5))(3) to produce compound 9 in high yield. Oxidation of 11 with PCC, allowed the introduction of 3,6-ene-dione functionality, and further catalytic hydrogenation and deprotection furnished the 3,6-diketo steroid 1.