35 research outputs found

    Level of accumulation of epoxy fatty acid in Arabidopsis thaliana expressing a linoleic acid Δ12-epoxygenase is influenced by the availability of the substrate linoleic acid

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    Arabidopsis thaliana (L.) Heynh. expressing the Crepis palaestina (L.) linoleic acid Δ12-epoxygenase in its developing seeds typically accumulates low levels of vernolic acid (12,13-epoxy-octadec-cis-9-enoic acid) in comparison to levels found in seeds of the native C. palaestina. In order to determine some of the factors limiting the accumulation of this unusual fatty acid, we have examined the effects of increasing the availability of linoleic acid (9cis, 12cis-octadecadienoic acid), the substrate of the Δ12-epoxygenase, on the quantity of epoxy fatty acids accumulating in transgenic A. thaliana. The addition of linoleic acid to liquid cultures of transgenic plants expressing the Δ12-epoxygenase under the control of the cauliflower mosaic virus35S promoter increased the amount of vernolic acid in vegetative tissues by 2.8-fold. In contrast, the addition to these cultures of linoelaidic acid (9trans, 12trans-octadecadienoic acid), which is not a substrate of the Δ12-epoxygenase, resulted in a slight decrease in vernolic acid accumulation. Expression of the Δ12-epoxygenase under the control of the napin promoter in the A. thaliana triple mutant fad3/fad7-1/fad8, which is deficient in the synthesis of tri-unsaturated fatty acids and has a 60% higher level of linoleic acid than the wild type, was found to increase the average vernolic acid content of the seeds by 55% compared to the expression of the Δ12-epoxygenase in a wild-type background. Together, these results reveal that the availability of linoleic acid is an important factor affecting the synthesis of epoxy fatty acid in transgenic plant

    In vitro activity of commercial probiotic Lactobacillus strains against uropathogenic Escherichia coli

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    Urinary tract infection (UTI) is one of the most prevalent infections in humans. In ≥80% of cases, the etiologic agents are strains of uropathogenic Escherichia coli (UPEC), which commonly reside in the gastrointestinal tract. Lactobacilli have been shown to prevent UTI reoccurrence by restoring the urogenital microbiota when administered vaginally or orally. The goal of this study was to determine if commercial probiotic Lactobacillus spp. reduce or clear UPEC in vitro. Results show that it is likely that lactobacilli may, in addition to restoring a healthy urogenital microbiota through acidification of their environment, also displace adhering UPEC and cause a reduction of infectio

    Global transcriptome analysis of the heat shock response of Bifidobacterium longum

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    Bifidobacteria are natural inhabitants of the human gastrointestinal tract and have been widely used as functional foods in different products. During industrial processing, bacterial cells undergo several stresses that can limit large-scale production and stability of the final product. To better understand the stress-response mechanisms of bifidobacteria, microarrays were used to obtain a global transcriptome profile of Bifidobacterium longum NCC2705 exposed to a heat shock treatment at 50°C for 3, 7 and 12 min. Gene expression data highlighted a profound modification of gene expression, with 46% of the genes being altered. This analysis revealed a slow-down of Bi. longum general metabolic activity during stress with a simultaneous activation of the classical heat shock stimulon. Moreover, the expression of several genes with unknown function was highly induced under stress conditions. Three of these were conserved in other bacteria species where they were also previously shown to be induced by high temperature, suggesting their widespread role in the heat stress response. Finally, the implication of the trans-translation machinery in the response of Bi. longum cells to heat shock was suggested by the induction of the gene encoding the tmRNA-associated small protein B (SmpB) with concomitant high constitutive expression of the tmRNA gen

    New method for selection of hydrogen peroxide adapted bifidobacteria cells using continuous culture and immobilized cell technology

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    <p>Abstract</p> <p>Background</p> <p>Oxidative stress can severely compromise viability of bifidobacteria. Exposure of <it>Bifidobacterium </it>cells to oxygen causes accumulation of reactive oxygen species, mainly hydrogen peroxide, leading to cell death. In this study, we tested the suitability of continuous culture under increasing selective pressure combined with immobilized cell technology for the selection of hydrogen peroxide adapted <it>Bifidobacterium </it>cells. Cells of <it>B. longum </it>NCC2705 were immobilized in gellan-xanthan gum gel beads and used to continuously ferment MRS medium containing increasing concentration of H<sub>2</sub>O<sub>2 </sub>from 0 to 130 ppm.</p> <p>Results</p> <p>At the beginning of the culture, high cell density of 10<sup>13 </sup>CFU per litre of reactor was tested. The continuous culture gradually adapted to increasing H<sub>2</sub>O<sub>2 </sub>concentrations. However, after increasing the H<sub>2</sub>O<sub>2 </sub>concentration to 130 ppm the OD of the culture decreased to 0. Full wash out was prevented by the immobilization of the cells in gel matrix. Hence after stopping the stress, it was possible to re-grow the cells that survived the highest lethal dose of H<sub>2</sub>O<sub>2 </sub>and to select two adapted colonies (HPR1 and HPR2) after plating of the culture effluent. In contrast to HPR1, HPR2 showed stable characteristics over at least 70 generations and exhibited also higher tolerance to O<sub>2 </sub>than non adapted wild type cells. Preliminary characterization of HPR2 was carried out by global genome expression profile analysis. Two genes coding for a protein with unknown function and possessing trans-membrane domains and an ABC-type transporter protein were overexpressed in HPR2 cells compared to wild type cells.</p> <p>Conclusions</p> <p>Our study showed that continuous culture with cell immobilization is a valid approach for selecting cells adapted to hydrogen peroxide. Elucidation of H<sub>2</sub>O<sub>2 </sub>adaptation mechanisms in HPR2 could be helpful to develop oxygen resistant bifidobacteria.</p

    Gut microbiota analysis reveals a marked shift to bifidobacteria by a starter infant formula containing a synbiotic of bovine milk-derived oligosaccharides and Bifidobacterium animalis subsp. lactis CNCM I-3446.

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    Non-digestible milk oligosaccharides were proposed as receptor decoys for pathogens and as nutrients for beneficial gut commensals like bifidobacteria. Bovine milk contains oligosaccharides, some of which are structurally identical or similar to those found in human milk. In a controlled, randomized double-blinded clinical trial we tested the effect of feeding a formula supplemented with a mixture of bovine milk-derived oligosaccharides (BMOS) generated from whey permeate, containing galacto-oligosaccharides and 3'- and 6'-sialyllactose, and the probiotic Bifidobacterium animalis subsp. lactis (B. lactis) strain CNCM I-3446. Breastfed infants served as reference group. Compared with a non-supplemented control formula, the test formula showed a similar tolerability and supported a similar growth in healthy newborns followed for 12 weeks. The control, but not the test group, differed from the breast-fed reference group by a higher faecal pH and a significantly higher diversity of the faecal microbiota. In the test group the probiotic B. lactis increased by 100-fold in the stool and was detected in all supplemented infants. BMOS stimulated a marked shift to a bifidobacterium-dominated faecal microbiota via increases in endogenous bifidobacteria (B. longum, B. breve, B. bifidum, B. pseudocatenulatum)

    Effect of Lactobacillus rhamnosus CGMCC1.3724 supplementation on weight loss and maintenance in obese men and women

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    The present study investigated the impact of a Lactobacillus rhamnosus CGMCC1.3724 (LPR) supplementation on weight loss and maintenance in obese men and women over 24 weeks. In a double-blind, placebo-controlled, randomised trial, each subject consumed two capsules per d of either a placebo or a LPR formulation (1·6×108 colony-forming units of LPR/capsule with oligofructose and inulin). Each group was submitted to moderate energy restriction for the first 12 weeks followed by 12 weeks of weight maintenance. Body weight and composition were measured at baseline, at week 12 and at week 24. The intention-to-treat analysis showed that after the first 12 weeks and after 24 weeks, mean weight loss was not significantly different between the LPR and placebo groups when all the subjects were considered. However, a significant treatment×sex interaction was observed. The mean weight loss in women in the LPR group was significantly higher than that in women in the placebo group (P=0·02) after the first 12 weeks, whereas it was similar in men in the two groups (P=0·53). Women in the LPR group continued to lose body weight and fat mass during the weight-maintenance period, whereas opposite changes were observed in the placebo group. Changes in body weight and fat mass during the weight-maintenance period were similar in men in both the groups. LPR-induced weight loss in women was associated not only with significant reductions in fat mass and circulating leptin concentrations but also with the relative abundance of bacteria of the Lachnospiraceae family in faeces. The present study shows that the Lactobacillus rhamnosus CGMCC1.3724 formulation helps obese women to achieve sustainable weight los

    Impact of Unusual Fatty Acid Synthesis on Futile Cycling through β-Oxidation and on Gene Expression in Transgenic Plants

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    Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal β-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward β-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through β-oxidation than the expression profile of genes involved in lipid metabolism

    Structure and Expression Profile of the Arabidopsis PHO1 Gene Family Indicates a Broad Role in Inorganic Phosphate Homeostasis

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    PHO1 has been recently identified as a protein involved in the loading of inorganic phosphate into the xylem of roots in Arabidopsis. The genome of Arabidopsis contains 11 members of the PHO1 gene family. The cDNAs of all PHO1 homologs have been cloned and sequenced. All proteins have the same topology and harbor a SPX tripartite domain in the N-terminal hydrophilic portion and an EXS domain in the C-terminal hydrophobic portion. The SPX and EXS domains have been identified in yeast (Saccharomyces cerevisiae) proteins involved in either phosphate transport or sensing or in sorting proteins to endomembranes. The Arabidopsis genome contains additional proteins of unknown function containing either a SPX or an EXS domain. Phylogenetic analysis indicated that the PHO1 family is subdivided into at least three clusters. Reverse transcription-PCR revealed a broad pattern of expression in leaves, roots, stems, and flowers for most genes, although two genes are expressed exclusively in flowers. Analysis of the activity of the promoter of all PHO1 homologs using promoter-β-glucuronidase fusions revealed a predominant expression in the vascular tissues of roots, leaves, stems, or flowers. β-Glucuronidase expression is also detected for several promoters in nonvascular tissue, including hydathodes, trichomes, root tip, root cortical/epidermal cells, and pollen grains. The expression pattern of PHO1 homologs indicates a likely role of the PHO1 proteins not only in the transfer of phosphate to the vascular cylinder of various tissues but also in the acquisition of phosphate into cells, such as pollen or root epidermal/cortical cells
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