Temperature-dependent induction of an acid-inducible stimulon of Escherichia coli in broth.

The induction of the inducible lysyl-tRNA synthetase, LysU, and the inducible lysine and arginine decarboxylases of Escherichia coli K-12 grown in AC broth to a pH of 5.5 or less is temperature dependent, being distinctly lower at 24 than at 37 degrees C. This induction does not appear to be under HtpR control.     

Crystal and molecular structure of two geometrically restricted chemotactic tripeptides, analogues of formyl-methionine-leucine-phenylalanine

The crystal structures of HCO-Met-Leu-Phe-OC(CH3)3, (CH25H39N3O5S), fMLP-OtBu, and HCO-Met psi [CSNH]-Leu-Phe-OCH3, (C22H33N3O4S2), fMS LP-OMe, have been determined by single crystal X-ray diffraction, and their conformational properties investigated by molecular mechanics energy calculations. Crystals of fMLP-OtBu are monoclinic, space group P2(1), a = 12.027(4), b = 9.492(3), c = 12.660(4) A, beta = 101.99(3) degrees, Z = 2; those of fMS LP-OMe are orthorhombic, space group P2(1)2(1)2(1), a = 7.130(1), b = 12.097(2), c = 31.060(5) A, Z = 4. The first compounds fMLP-OtBu is the t-butyl ester of the tripeptide fMLP that represents one of the most potent compounds in inducing the lysozyme release from human neutrophils that reflects the chemotactic activity. From the crystal structure, it is shown that the orientation of the phenylalanine side chain is largely affected by the presence of the bulky group. fMSLP-OMe was shown to be inactive after thionation of the methionine residue in the original tripeptide. Nevertheless, the crystal structure does not reveal any influence of the presence of the thionated peptidic bond on the backbone conformation. The X-ray results have been used to generate parameters for empirical energy calculations. Subsequently, a strategy based on random generation of conformations followed by energy-minimization was applied to investigate the conformational space of thiopeptides, in comparison with normal peptides. From molecular free energy calculations, it is shown that the main influence of the introduction of a thioamide bond on the molecular structure is to prevent the existence of C7(eq) conformations involving the thiomethionine residue. Consequently, a larger number of conformers are found to form intramolecular hydrogen bonds involving the formyl group, reducing its availability to interact with the receptor. For the first time, the theoretical prediction of the existence of C7eq conformations for fMLP is made. The resulting conformers are compared to previously active structures of these chemotactic agents.     

Virulence Increasing of <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> in Balb/c Mice After Heat-Stress Induction of Phage Shock Protein A

Salmonella typhimurium is a potentially intracellular pathogen and is responsible for thousands of reported cases of acute gastroenteritis and diarrhea each year. Although many successful physiological and genetic approaches have been taken to conclude the key virulence determinants encoded by this organism, the total number of uncharacterized reading frames observed within the S. typhimurium genome suggests that many virulence factors remain to be discovered. This study was conducted to evaluate the role of heat induced phage shock protein A (PspA), in the pathogenicity of S. typhimurium. The stress proteins detected on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were identified specifically by immunoblotting with polyclonal antibody against PspA. PspA was produced in response to heat stress at 45°C and it was over-expressed at 65°C. At this temperature, the stressed bacterial cells producing PspA were more virulent (16 folds greater) to female 6–8 week-old Balb/c mice. Correspondency between decrease in LD₅₀ and increase in PspA production during heat stress and lower pathogenicity in non-producing cells that emerged during stress at 55°C represents PspA as an important virulence factor in heat stressed S. typhimurium.     

Development of 4-cell mouse embryos after re-vitrification

This paper reports studies on the effects of re-vitrification by the CPS (Closed Pulled Straw) method on the development of 4-cell stage mouse embryos. The procedure involved culturing 2-cell mouse embryos in G-1 medium until the 4-cell stage followed by the division of the normal 4-cell stage embryos into a control group (non-vitrified) and two experimental subgroups (vitrified and re-vitrified). Embryos in the vitrified subgroup were cryopreserved by the CPS vitrification method. In the second experimental subgroup (re-vitrified), embryos that were already vitrified were warmed and cryopreserved again by the same method. There was no significant reduction in the rate of blastocyst formation after vitrification and re-vitrification. However, re-vitrification reduced the total cell number, ICM (inner cell mass) percent and blastocyst diameter (P<0.05). These results showed that vitrification and re-vitrification by the CPS method did not negatively affect the development of vitrified-warmed 4-cell mouse embryos, whereas re-vitrification significantly reduced both the cell number and diameter of blastocysts.     

Coproporphyrin III excretion identifies the anaerobic coproporphyrinogen III oxidase HemN as a copper target in the Cu+‐ATPase mutant copA− of Rubrivivax gelatinosus

Two genes encoding structurally similar Copper P_1B‐type ATPases can be identified in several genomes. Notwithstanding the high sequence and structural similarities these ATPases held, it has been suggested that they fulfil distinct physiological roles. In deed, we have shown that the Cu⁺‐ATPase CtpA is required only for the activity of cuproproteins in the purple bacterium Rubrivivax gelatinosus; herein, we show that CopA is not directly required for cytochrome c oxidase but is vital for copper tolerance. Interestingly, excess copper in the copA^? mutant resulted in a substantial decrease of the cytochrome c oxidase and the photosystem under microaerobic and anaerobic conditions together with the extrusion of coproporphyrin III. The data indicated that copper targeted the tetrapyrrole biosynthesis pathway at the level of the coproporphyrinogen III oxidase HemN and thereby affects the oxidase and the photosystem. This is the first in vivo demonstration that copper, like oxygen, affects tetrapyrrole biosynthesis presumably at the level of the SAM and [4Fe‐4S] containing HemN enzyme. In light of these results and similar findings in Escherichia coli, the potential role of copper ions in the evolution of [4Fe‐4S] enzymes and the Cu⁺‐ATPases is discussed.     

The Blepharis persica seed hydroalcoholic extract synergistically enhances the apoptotic effect of doxorubicin in human colon cancer and gastric cancer cells

The goal of this survey is to evaluate the anti-proliferative effects of the hydroalcholic extract of Blepharis persica seeds and its synergic effect on doxorubicin (DOX) in human colon cancer (HT-29) and gastric cancer cell (AGS) lines. 70% Ethanol was used for extraction of B. persica seed. Aluminum–chloride colorimetric and Folin–Ciocalteu reagent methods were used to measure total flavonoid and total phenolic contents of the extract respectively. Gas chromatography-mass spectrometry (GC-MS) analysis of the B. persica extract was performed on GC-MS equipment after silylation. HT-29, AGS, and human fibroblast (SKM) cell lines were treated by different concentration of the B. persica extract, (DOX) and the combination of extraction and DOX. The cytotoxicity was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay while the apoptosis induction was monitored using flowcytometry by annexin-V FITC/PI double-staining. The changes in expression levels of BAX and BCL-2 were determined using Real-Time RT-qPCR. GC-MS analysis of the hydroalcoholic extract from B. persica seeds revealed 24 major components. The MTT assay revealed the cytotoxicity against three cell lines and also it was shown that 125 ng/mL of DOX and 0.625 mg/mL of B. persica extract had synergistic behavior against HT29 cell line. These results showed B. persica extract induced apoptosis in AGS and HT29 cells and its extract caused dose-dependent increase in up-regulation of BAX level (p?<?0.05) and down-regulation of BCL₂ (p?<?0.05). B. persica showed the synergistic effect in combination with DOX on HT29 cell line. These findings demonstrated a basis for further studies on the characterization and mechanistic evaluation of the bioactive compounds of B. persica extract which had antiproliferative effects on cancer cell lines.

     

The role of livestock movements in the spread of Rift Valley fever virus in animals and humans in Mayotte, 2018–19

Rift Valley fever (RVF) is a vector-borne viral disease of major animal and public health importance. In 2018–19, it caused an epidemic in both livestock and human populations of the island of Mayotte. Using Bayesian modelling approaches, we assessed the spatio-temporal pattern of RVF virus (RVFV) infection in livestock and human populations across the island, and factors shaping it. First, we assessed if (i) livestock movements, (ii) spatial proximity from communes with infected animals, and (iii) livestock density were associated with the temporal sequence of RVFV introduction into Mayotte communes’ livestock populations. Second, we assessed whether the rate of human infection was associated with (a) spatial proximity from and (b) livestock density of communes with infected animals. Our analyses showed that the temporal sequence of RVFV introduction into communes’ livestock populations was associated with livestock movements and spatial proximity from communes with infected animals, with livestock movements being associated with the best model fit. Moreover, the pattern of human cases was associated with their spatial proximity from communes with infected animals, with the risk of human infection sharply increasing if livestock in the same or close communes were infected. This study highlights the importance of understanding livestock movement networks in informing the design of risk-based RVF surveillance programs.     

Antibacterial activity of Thymus maroccanus and Thymus broussonetii essential oils against nosocomial infection - bacteria and their synergistic potential with antibiotics

The aim of this study was to evaluate the antibacterial effect of the association between conventional antibiotics and essential oils (EOs) of endemic Moroccan thyme species, Thymus maroccanus and T. broussonetii, on antibiotic-resistant bacteria involved in nosocomial infections. Synergistic interactions between antibiotics (ciprofloxacin, gentamicin, pristinamycin, and cefixime) and EOs, and between T. maroccanus and T. Broussonetii EOs were determined by the checkerboard test. Serial dilutions of two antimicrobial agents were mixed together so that each row (and column) contained a fixed amount of the first agent and increasing amounts of the second one. The results indicate that the oils had a high inhibitory activity against tested bacteria, except for Pseudomonas aeruginosa. In parallel with the increase of cellular killing, the release of 260nm-absorbing materials from bacterial cells, treated with EOs, increased in response to oil concentration. Out of 80 combinations tested between EOs and antibiotics, 71% showed total synergism, 20% had partial synergistic interaction and 9% showed no effect. Combination with carvacrol, the major constituent of T. maroccanus and T. broussonetii, showed also an interesting synergistic effect in combination with ciprofloxacin. The effect on Gram-positive bacteria was more important than on Gram-negative bacteria. These findings are very promising since the use of these combinations for nosocomial infections treatment is likely to reduce the minimum effective dose of the antibiotics, thus minimizing their possible toxic side effects and treatment cost. However, further investigations are needed to assess the potential for therapeutic application.     

Chemical composition and antioxidant and anticandidal activities of essential oils from different wild Moroccan Thymus species

Samples of the aerial parts of Thymus broussonetii, T. ciliatus, T. leptobotrys, T. maroccanus, T. pallidus, T. satureioides, and T. serpyllum collected from different natural regions in southern and south-western Morocco were analyzed for their qualitative and quantitative essential oil profiles. In total, 46 compounds, representing more than 99% of the oils, were characterized. Monoterpenes, both hydrocarbons (12.9-58.0%) and oxygenated monoterpenes (38.8-81.1%), were the principal classes of compounds for most of the thyme species studied. Cluster analysis allowed the classification of the species into three main groups: a carvacrol group (Group I), comprising the species T. maroccanus and T. leptobotrys, a linalyl acetate and (E)-nerolidol group (Group II), represented by T. serpyllum, and a thymol and/or carvacrol, γ-terpinene, and p-cymene group (Group III), composed of T. satureioides, T. broussonetii, T. ciliatus, and T. pallidus. The essential oils were screened for their antioxidant and anticandidal activities. The data showed that the oils obtained from T. leptobotrys and T. maroccanus (carvacrol group) possessed the highest antioxidant activities as assessed by the determination of the DPPH free radical-scavenging ability and the ferric-reducing potential. The anticandidal assays indicated that the highest activity was noticed for the essential oil isolated from T. leptobotrys.     

Essential oil composition and antimicrobial activity of wild and cultivated Moroccan Achillea ageratum L.: a rare and threatened medicinal species

The essential oils of leaves and flowers of the wild and cultivated Moroccan Achillea ageratum L., a rare and threatened medicinal species, were examined by GC/MS, and their chemical compositions were compared. At least nine components were identified in both wild and cultivated A. ageratum oils, representing more than 95% of the oils. Artemisyl acetate (62.34-78.79%), yomogi alcohol (4.89-12.40%), santolina alcohol (4.86-11.77%), and artemisia alcohol (3.36-7.04%) were the major compounds. Terpene-alcohol proportion was higher in wild A. ageratum than in cultivated A. ageratum. The antibacterial analysis showed that both oils presented high activity against all the studied Gram-positive strains in a range of MIC values from 2.55 to 7.02?mg/ml, but they appeared not effective against the tested Gram-negative ones (MIC values 20.40-41.10?mg/ml). They also exhibited remarkable antifungal activities against Candida species with MIC values ranging from 5.83 to 8.42?mg/ml. From these results, it was concluded that domestication of this threatened medicinal species using clonal propagation did not significantly affect its chemical composition and consequently its antimicrobial properties.