Toxicity of antibiotic oxytetracycline, an emerging aquatic micropollutant, on the freshwater microalga "Haematococcus pluvialis" Flotow

Traballo fin de grao (UDC.CIE). Bioloxía. Curso 2016/2017[Resumen] La presencia de contaminantes emergentes en el medio acuático, como los antibióticos, suponen un grave problema, ya que puede dañar organismos no diana como las microalgas, responsables de la producción primaria en estos ecosistemas. En la actualidad, el antibiótico oxitetraciclina es uno de los fármacos más utilizados en múltiples sectores como la medicina, veterinaria, ganadería o piscicultura, debido a su alto rendimiento, teniendo actividad frente a una amplia gama de bacterias gram-positivas y gram-negativas y por su bajo coste. En el presente trabajo se estudió el posible efecto tóxico del microcontaminante emergente oxitetraciclina (OTC) sobre la microalga dulceacuícola Haematococcus pluvialis. Con este fin, se expusieron los cultivos a diferentes concentraciones de oxitetraciclina (0,5, 1, 2,5, 5 y 10 mg l-1) durante 96 horas. Además se llevaron a cabo cultivos control a los que no se les adicionó el antibiótico estudiado. Del mismo modo, para estudiar el potencial efecto de la temperatura sobre la toxicidad de este contaminante en el marco del calentamiento global, los ensayos se llevaron a cabo a dos temperatura diferentes: 18ºC y 24ºC. Transcurrido ese tiempo se analizaron los parámetros de crecimiento, viabilidad celular y contenido en clorofila a. Además, también se estudió el posible efecto de la exposición a OTC sobre la producción del carotenoide astaxantina, mediante el análisis de su contenido celular. Por último, se procedió al estudio de células vegetativas flageladas frente al porcentaje de células en estado palmeloide así como la acumulación de lípidos neutros en dichas células. En los cultivos mantenidos a 18ºC, la exposición al antibiótico provocó una inhibición significativa del crecimiento, de la viabilidad celular y del contenido en clorofila a en los cultivos de Haematococcus pluvialis, frente a cultivos control sin contaminante (p-valor0,05), incrementándose también el porcentaje de células palmeloides (p-valor0.05) and an increase in the percentage of palmeloid cells (p-value<0.05) as well as in the percentage of cells rich in neutral lipids (p-value<0.05). Optical microscope observation of these cultures showed the presence of morphological changes in H. pluvialis cells exposed to OTC previously described in this species in response to different stress situations. This response is characterized by a decrease in the chlorophyll a content due to the inhibition of photosynthesis leading to the formation of the pigment astaxanthin, thus reducing the presence of vegetative cells in a flagellated motile state and increasing the percentage of cells in stationary and non-flagellated resistance with accumulation of astaxanthin and neutral lipids. In parallel to these tests, the existence of a possible interaction between an environmental factor (temperature) and exposure to oxytetracycline with H. pluvialis cultures maintained at 24ºC was also evaluated. After 96 h of exposure, there was an interaction between both variables for cell viability, chlorophyll a content, astaxanthin content and percentage of palmeloid cells (p-value <0.05), indicating that the temperature increase reduced the toxic effect of the antibiotic

Bleriot-Spad 91 Airplane (French) : pursuit single-seater, type "Jockey"

This aircraft has announced a speed of 270 km per hour at 4000 m. It is of all metal construction

An investigation of regional income and employment multipliers in forest based industries in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Geography at Massey University

Page 124 is missing from original copy.Income and employment multipliers are used to estimate the likely impact of forest-based industries in four regions of New Zealand: Northland, Rotorua, Westland, and Otago. The results obtained for each region are used to determine the variability of multipliers from one region to another and to evaluate the loss of potential income and employment as a consequence of leakage effects. Regional income multipliers are calculated using the Keynesian model while regional employment multipliers are calculated using an ad hoc model designed to take into consideration the influences of regional variations in under-employment. The data for the study were obtained from a questionnaire survey of sector plants and employees in each study region. Where appropriate supporting data were derived from published statistics. Estimated values for the calculated multipliers fall between 1.20 and 1.80. These figures suggest that the leakage factor resulting from high regional imports, taxation, and unspent profits may be larger than previously believed. It is also concluded that regional income and employment multipliers vary from one region to another for a wide variety of reasons, many of which relate to plant characteristics rather than to regional characteristics. For this reason it may be more appropriate to calculate multipliers for individual plants in the regional context rather than regional multipliers based on the combined and multivariate impacts of a group of plants

Inhibition de la corrosion d'un acier au carbone par des produits dérivés de phosphonates en association avec des sels de zinc

Dans cette étude, des mesures électrochimiques ont été utilisées pour caractériser l'efficacité inhibitrice de produits dérivés de phosphonates associés à des sels de zinc, employés pour le traitement des eaux des circuits de refroidissement. L'influence de la concentration de cette formulation ainsi que l'effet du pH du milieu ont été étudiés.Les courbes courant-tension stationnaires et les diagrammes d'impédance électrochimique ont été obtenus avec des électrodes tournantes en acier au carbone dans une solution de chlorure de sodium à 200 mg l-1. Ce milieu a été choisi car sa faible conductivité électrique est proche de celle rencontrée dans les eaux naturelles.La méthode stationnaire (relevé des courbes courant-tension) a permis de déterminer la vitesse de corrosion en l'absence et en présence de l'inhibiteur et par conséquent, le taux de protection. Ainsi, le composé présente une très bonne efficacité dès les faibles concentrations (50 mg · l-1). Entre 50 et 200 mg · l-1, l'efficacité inhibitrice augmente de 95 à 98 %. Pour la concentration de 100 mg · l-1 il est efficace dans un large domaine de pH (de 5,5 à 9). Cette efficacité apparaît légèrement supérieure à pH = 7 et à pH = 8.Les valeurs des résistances de polarisation mesurées à partir des diagrammes d'impédance confirment les résultats obtenus à partir des courbes stationnaires.En outre, l'efficacité inhibitrice du composé a été comparée à celle de produits déjà testés au Laboratoire pour des utilisations identiques. Le chlorure de zinc, le monofluorophosphate de zinc et l'association d'une amine grasse et d'acide phosphonique présentent des efficacités moindres que le mélange testé ici à base de produits dérivés de phosphonates associés aux sels de zinc.In this study, electrochemical measurements were carried out to characterize the inhibitive efficiency of the association of phosphonate-derived products with zinc salts, employed for water treatment in cooling circuits.The influence of parameters such as the concentration of the formulation and the effect of the solutions pH on the protection of the metal were studied.Steady-state current-voltage curves and electrochemical impedance diagrams have been obtained for a carbon steel rotating disc in a 200 mg · l-1 NaCl solution. The choice of this medium is based upon the following criteria :(i) its low electrical conductivity is close to that encountered in natural saline waters ;(ii) its corrosivity is fairly high ;(iii) it Is formed by an easily reproducible baseline solution.The inhibitive efficiency has been determined tram the plotting of the cathodic potentiostatic curves. It is important to note that in low conductivity media, the current-voltage curves are distorted by a non-negligible uncompensated ohmic drop (I.Re), Re being the electrolyte resistance between the working and the reference electrodes. The interpretation of these curves (i.e. corrosion rate evaluation, Tafel slopes determination) is only possible if they have been corrected according to the following relationship. Eapparent = Etrue + ReIIn this study, the electrolytic resistance value has been determined from electrochemical Impedance measurements : the high frequency limit of the impedance gives Re.The ohmic drop is then automatically compensated by the potentiostat to obtain the corrected steady-state curve.The inhibitive efficiency is evaluated by the relationship :Ei = (icorr0-icorr / icorr0) x 100in which iocorr and icorr represent the current densities without and with inhibitor, respectively.In addition to the determination of the current densities obtained from the steady-state current-voltage curves, the polarization resistance, Rp, has been measured from the impedance diagram : the low frequency limit of the impedance gives the sum Re + Rp ; Rp is equal to the slope of the steady-state current voltage curve.In this study, only the evolution of this value as a function of concentration has been examined.It has been shown from the steady-state technique that the compound presents a very good efficiency for low concentrations (50 mg · l-1). Between 50 and 200 mg · l-1, the inhibitive efficiency increases from 95 to 98 %. For 100 mg · l-1 it is effective over a wide pH range (5.5 to 9) with a better protection for pH = 7 and pH = 8.The measurements of the polarization resistance corroborate these results.In a second part, the inhibitive efficiency of the compound has been compared to different inhibitors used for similar uses and tested in the laboratory. Thus, zinc chloride, zinc fluorophosphate and the association of fatty amine and phosphonic acid present a lower efficiency than the product tested here

Éclairage [Material gráfico proyectable]

Contiene: 1. Peinture et lampe prehistoriques ; 2. Lampes artistiques grecaues romaine ; 3. Un autel ; 4. Un cirier et un chandelier au 18e S. ; 5. Une coulerie de bougie ; 6. Le gues ; 7. Bourgeois allumans les chandelles ; 8. Proust et la lampe ; 9. Lampe Argand ; 10. Lampe Carcel ; 11. Loi du Carré ; 12. Les photometres ; 13. Philippe Lebon ; 14. Les premiers becs de gas [Lampe Wenhan] ; 15. Appareil á lumieré ; 16. Le bec auer ; 17. Lamberne de 100 carcels ; 18. [Puits] de petrole en feu ; 19. Lampe a petrole ; 20. La lampe toute Puissante ; 21. Une lampe phare ; 22. Pile de Davy ; 23. L'arc de Foucault ; 24. Mecanisme de lampe á arc ; 25. Lampe á incandescence ; 26. Un salon eclaire avec des lampes à incandescence ; 27. Phare d' Alexandrie ; 28. Phare de Genes ; 29. Reclame lumineuse ; 30. Les tubes MooreCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 2015En el grab. 21 consta Bleriot.Elie Mazo publicas estas colecciones en el primer cuarto del s. XX.Placas epidioscópicas de grab. sobre vidrio, las dimensiones son 7 x 4, 5 cm o menos

RcnB Is a Periplasmic Protein Essential for Maintaining Intracellular Ni and Co Concentrations in Escherichia coli

International audienceNickel and cobalt are both essential trace elements that are toxic when present in excess. The main resistance mechanism that bacteria use to overcome this toxicity is the efflux of these cations out of the cytoplasm. RND (resistance-nodulation-cell division)- and MFS (major facilitator superfamily)-type efflux systems are known to export either nickel or cobalt. The RcnA efflux pump, which belongs to a unique family, is responsible for the detoxification of Ni and Co in Escherichia coli. In this work, the role of the gene yohN, which is located downstream of rcnA, is investigated. yohN is cotranscribed with rcnA, and its expression is induced by Ni and Co. Surprisingly, in contrast to the effect of deleting rcnA, deletion of yohN conferred enhanced resistance to Ni and Co in E. coli, accompanied by decreased metal accumulation. We show that YohN is localized to the periplasm and does not bind Ni or Co ions directly. Physiological and genetic experiments demonstrate that YohN is not involved in Ni import. YohN is conserved among proteobacteria and belongs to a new family of proteins; consequently, yohN has been renamed rcnB. We show that the enhanced resistance of rcnB mutants to Ni and Co and their decreased Ni and Co intracellular accumulation are linked to the greater efflux of these ions in the absence of rcnB. Taken together, these results suggest that RcnB is required to maintain metal ion homeostasis, in conjunction with the efflux pump RcnA, presumably by modulating RcnA-mediated export of Ni and Co to avoid excess efflux of Ni and Co ions via an unknown novel mechanism

Phenotypic and Genomic Comparison of Klebsiella pneumoniae Lytic Phages: vB_KpnM-VAC66 and vB_KpnM-VAC13

Klebsiella pneumoniae is a human pathogen that worsens the prognosis of many immuno compromised patients. Here, we annotated and compared the genomes of two lytic phages that infect clinical strains of K. pneumoniae (vB_KpnM-VAC13 and vB_KpnM-VAC66) and phenotypically char acterized vB_KpnM-VAC66 (time of adsorption of 12 min, burst size of 31.49 ± 0.61 PFU/infected cell, and a host range of 20.8% of the tested strains). Transmission electronic microscopy showed that vB_KpnM-VAC66 belongs to the Myoviridae family. The genomic analysis of the phage vB_KpnM VAC66 revealed that its genome encoded 289 proteins. When compared to the genome of vB_KpnM VAC13, they showed a nucleotide similarity of 97.56%, with a 93% of query cover, and the phylo genetic study performed with other Tevenvirinae phages showed a close common ancestor. How ever, there were 21 coding sequences which differed. Interestingly, the main differences were that vB_KpnM-VAC66 encoded 10 more homing endonucleases than vB_KpnM-VAC13, and that the nu cleotidic and amino-acid sequences of the L-shaped tail fiber protein were highly dissimilar, leading to different three-dimensional protein predictions. Both phages differed significantly in their host range. These viruses may be useful in the development of alternative therapies to antibiotics or as a co-therapy increasing its antimicrobial potential, especially when addressing multidrug resistant (MDR) pathogens.Instituto de Salud Carlos III: PI19/0087

Enhanced antibacterial activity of repurposed mitomycin C and imipenem in combination with the lytic phage vB_KpnMVAC13 against clinical isolates of klebsiella pneumoniae

Klebsiella pneumoniae is an opportunistic Gram-negative pathogen that employs different strategies (resistance and persistence) to counteract antibiotic treatments. This study aimed to search for new means of combatting imipenem-resistant and persister strains of K. pneumoniae by repurposing the anticancer drug mitomycin C as an antimicrobial agent and by combining the drug and the conventional antibiotic imipenem with the lytic phage vB_KpnM-VAC13. Several clinical K. pneumoniae isolates were characterized, and an imipenem-resistant isolate (harboring OXA-245 β-lactamase) and a persister isolate were selected for study. The mitomycin C and imipenem MICs for both isolates were determined by the broth microdilution method. Time-kill curve data were obtained by optical density at 600 nm (OD600) measurement and CFU enumeration in the presence of each drug alone and with the phage. The frequency of occurrence of mutants resistant to each drug and the combinations was also calculated, and the efficacy of the combination treatments was evaluated using an in vivo infection model (Galleria mellonella). The lytic phage vB_KpnM-VAC13 and mitomycin C had synergistic effects on imipenem-resistant and persister isolates, both in vitro and in vivo. The phage-imipenem combination successfully killed the persisters but not the imipenem-resistant isolate harboring OXA-245 β-lactamase. Interestingly, the combinations decreased the emergence of in vitro resistant mutants of both isolates. Combinations of the lytic phage vB_KpnM-VAC13 with mitomycin C and imipenem were effective against the persister K. pneumoniae isolate. The lytic phage-mitomycin C combination was also effective against imipenem-resistant K. pneumoniae strains harboring OXA-245 β-lactamaseinstituto de Salud Carlos III RD16/0016/0001 RD16/0016/0006 RD16/CIII/0004/000

Towards novel difluorinated sugar mimetrics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones

Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT 19F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers

The role of PemIK (PemK/PemI) type II TA system from Klebsiella pneumoniae clinical strains in lytic phage infection

Since their discovery, toxin-antitoxin (TA) systems have captivated the attention of many scientists. Recent studies have demonstrated that TA systems play a key role in phage inhibition. The aim of the present study was to investigate the role of the PemIK (PemK/PemI) type II TA system in phage inhibition by its intrinsic expression in clinical strains of Klebsiella pneumoniae carrying the lncL plasmid, which harbours the carbapenemase OXA-48 and the PemK/PemI TA system. Furthermore, induced expression of the system in an IPTG-inducible plasmid in a reference strain of K. pneumoniae ATCC10031 was also studied. The results showed that induced expression of the whole TA system did not inhibit phage infection, whereas overexpression of the pemK toxin prevented early infection. To investigate the molecular mechanism involved in the PemK toxin-mediated inhibition of phage infection, assays measuring metabolic activity and viability were performed, revealing that overexpression of the PemK toxin led to dormancy of the bacteria. Thus, we demonstrate that the PemK/PemI TA system plays a role in phage infection and that the action of the free toxin induces a dormant state in the cells, resulting in inhibition of phage infections