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Discovering the Potential of Microalgae-Bacterial Consortia for New Strategies in Fighting off Bacterial Biofilms
No full textBacterial biofilms are comparable to organs complex structures that provide protection and nutrition to their inhabitants. The biofilm matrix shields embedded bacteria by trapping antibiotics, toxins and agents of the host immune system at the surface while inside the biofilm bacteria enhance their endurance through genetic exchange, physiological heterogeneity and metabolic reduction. Due to their highly resilient character, biofilms cause severe and costly problems in industry, farming and health care, with this study focusing particularly on challenges of the fast-growing sector of aquaculture. Facing the limited number of available antibiotics and in contrast the constantly growing antibiotic resistance in bacteria, new strategies are inevitable to address pathogenic bacteria and their sheltering surrounding.
Microalgae are small, unicellular organisms that successfully inhabit all kinds of aquatic environments displaying a worldwide distribution. Their cooperative lifestyle with beneficial bacteria shelters their survival in challenging environments and protects them efficaciously from pathogenic threads. Up to date little is known about the composition and the intrinsic potential of these microalgae-bacterial consortia. Hence, the present study focused on the potential of microalgae-bacterial consortia to influence biofilm formation of pathogenic bacteria. This question was addressed by data mining of newly established metagenomes and by practical application. First approaches made use of the total supernatant of various microalgae cultures to find out if there is any effect on bacterial biofilms proved by static anti-biofilm assay and, as effects were measurable, which microalgae’s supernatant showed the highest inhibiting effect in terms of biofilm reduction. Of 17 marine and freshwater microalgae cultures (data not entirely shown) the six candidates with the highest inhibitory results on bacterial biofilms of Pseudomonas aeruginosa PA14, Burkholderia cenocepatia K56-2, Stenotrophomonas maltophilia K279a, Stenotrophomonas maltophilia SM454 and Klebsiella pneumonie WT1617 were chosen for further investigation. The supernatant of the marine microalgae Tetraselmis chui reduced biofilm in all tested bacteria significantly by an average of 57.2%. Biofilm inhibition, if only for certain bacterial species each, was also observed for the supernatants of the marine microalgae Nannochloropsis salina, Isochrysis galbana and Isochrysis spec. as well as for the freshwater microalgae Chlorella vulgaris, and Scenedesmus acuminatus. The inhibitory potential of the total supernatants of microalgae cultures on the biofilm of P. aeruginosa PA14 was explored more deeply by laser scanning confocal microscopy (LSCM). Calculations of total cell numbers within a defined biofilm area revealed a decrease of 25% of P. aeruginosa cells after treatment with T. chui supernatant and alterations in biofilm architecture towards lower biofilm density.
Metagenomes of the six effective microalgae were prepared to first enlighten the phylogeny of the bacterial communities encompassing the individual microalgae and second to elucidate their enzymatic potential. Though all of the microalgae-bacterial consortia showed a prevalent fraction of proteobacteria with an emphasis on alphaproteobacteria, particularly apparent in T. chui, I. galbana and C. vulgaris, the composition of the consortia on genus level occurred highly divers. Only the marine bacteria Roseobacter, Roseovarius, Muricauda and Marinobacter appeared repeatedly within the metagenomes. Promising enzyme classes were explored and quantified for current and future use. Since bacterial biofilms promote virulence and decrease antibiotic susceptibility a multifaceted approach seems to be required to either alter the biofilm architecture for better access of classic antibiotics to the embedded pathogens or to weaken and ideally inhibit the process of biofilm formation. Hence, the metagenome data of the six microalgae-bacterial consortia should serve as a valuable toolbox for advances to interfere with key points in biofilm formation such as quorum sensing, initial attachment or accumulation of EPS (extracellular polymeric substances) with special regard to the role of extracellular DNA. First experiences with a microalgae-metagenome-derived enzyme were gained with a putative quorum quenching dienelactone hydrolase (Dlh3). Due to its intended application in aquaculture, Dlh3 was administered to the fish pathogens Edwardsiella anguillarum, Aeromonas salmonicida, P. aeruginosa, Flavobacterium columnare and Flavobacterium psychrophilum. Interactions of Dlh3 and the fish pathogens were analyzed in static anti-biofilm assays, LSCM, and oCelloScope, revealing decreased biofilm formation, e.g., for E. anguillarum of up to 54.4% in static anti-biofilm assay and alterations in biofilm construction in optical approaches. Encouraged by these impressions more target-specific enzymes were chosen from the newly prepared metagenome data of microalgae-bacterial consortia. The successfully overexpressed enzymes, a methylcytosine-specific restriction endonuclease, that cleaves DNA in a specific, modified context, an 8-oxoguanine deaminase, that alters external DNA and a second dienelactone hydrolase were characterized by phylogenetic and structural attributes. First applications of the enzymes on fish pathogens, analyzed by LSCM, had considerable effects on the viability and structure of the observed biofilms. Considering the harmlessness of the enzymes stated in toxicity assays, this study might be a path-breaking approach for a versatile attack on pathogenic biofilms to avoid bacterial adaptation and resistance to antibiotic treatment and simultaneously, by harboring a wide-range enzymatic toolbox, maintaining the flexibility to react to changing demands e.g. in the context of high-density farming as for aquaculture.Bakterielle Biofilme weisen vergleichbar mit Organen komplexe Strukturen auf, die den innewohnenden Bakterien Schutz und Nahrung gewähren. Die Biofilm Matrix schützt die Bakterien im Biofilm indem sie Antibiotika und Angriffe des Wirts‘ eigenen Immunsystems abfängt, während die Bakterien im Biofilm ihre Lebensfähigkeit durch genetischen Austausch, physiologische Heterogenität und Reduzierung des metabolischen Umsatzes steigern. Durch ihren starken protektiven Charakter verursachen Biofilme große Schäden und hohe Kosten in Industrie, Tierzucht und im Gesundheitswesen. Ein besonderes Augenmerk legt diese Studie auf die Herausforderungen im schnell wachsenden Sektor der Aquakultur. Im Bewusstsein der begrenzten Verfügbarkeit von und der stetig wachsenden Resistenz gegen die angewandten Antibiotika, ist es unerlässlich, neue Strategien gegen krankheitserregende Bakterien und ihre schützende Umgebung zu entwickeln.
Mikroalgen sind kleine, einzellige Organismen, die mit ihrer weltweiten Ausbreitung erfolgreich alle Arten von aquatischen Lebensräumen bewohnen. Die Kooperation mit Bakterien sichert ihr Überleben in herausfordernden Lebensräumen und schützt sie weitgehend vor Pathogenen. Über die Zusammensetzung der Mikroalgen-Bakterien-Gemeinschaften ist bisher wenig bekannt. Diese Studie untersucht daher eingehend das Potential von Mikroalgen-Bakterien-Gemeinschaften, Einfluss auf die Bildung von Biofilmen pathogener Bakterien zu nehmen. Dafür wurden Daten von neu etablierten Mikroalgen-Metagenomen analysiert und verschiedene praktische Anwendungen erprobt. Zunächst wurde der komplette Überstand von Mikroalgenkulturen genutzt um festzustellen, ob ein Effekt auf die Biofilmbildung pathogener Bakterien in einem statischen Anti-Biofilm-Assay messbar wäre, und welche Mikroalgenkulturen die stärkste biofilmreduzierende Wirkung erzielten. Von 17 getesteten marinen und Süßwasser Mikroalgenkulturen (Daten nicht vollständig dargestellt) wurden die
sechs Kulturen mit der stärksten inhibitorischen Wirkung auf die Biofilme der Bakterien Pseudomonas aeruginosa PA14, Burkholderia cenocepatia K56-2, Stenotrophomonas maltophilia K279a, S. maltophilia SM454 und Klebsiella pneumonie WT1617 für weitere Untersuchungen ausgewählt. Der Überstand der Mikroalge Tetraselmis chui, zeigte eine biofilmreduzierende Wirkung auf alle getesteten Bakterien mit einer durchschnittlichen Verminderung um 57.2%. Biofilminhibition, wenn auch jeweils nur für einzelne Pathogene, zeigten darüber hinaus die marinen Mikroalgen Nannochloropsis salina, Isochrysis galbana und Isochrysis spec. sowie die Süßwasser Mikroalgen Chlorella vulgaris und Scenedesmus acuminatus. Das inhibitorische Potential der kompletten Überstände von Mikroalgenkulturen auf den Biofilm von P. aeruginosa PA14 wurde tiefergehend mittels Laser scanning confocal microscopy (LSCM) ermittelt. Eine 25%ige Reduktion der absoluten Zellzahlen innerhalb eines definierten Bereichs eines P. aeruginosa Biofilms konnte nach Zugabe des Überstands der Mikroalge T. chui berechnet werden. Gleichzeitig veränderte sich die Architektur des P. aeruginosa Biofilms in Richtung einer geringeren Dichte.
Von den sechs wirkungsvollen Mikroalgen wurden Metagenome angefertigt, um die Phylogenie der kooperierenden Bakterien zu ergründen, sowie Einblicke in das enzymatische Potential der Mikroalgen-Bakterien-Gemeinschaften zu gewinnen. Trotzdem sich in allen Metagenomen ein hoher Anteil an Proteobakterien, vor allem Alpha Proteobakterien zeigte, insbesondere bei T. chui, I. galbana und C. vulgaris, herrschte auf Genus-Level hohe Diversität. Einzig die marinen Bakterien Roseobacter, Roseovarius, Muricauda and Marinobacter waren in mehreren Metagenomen nachweisbar. Des Weiteren wurden mögliche wirkungsvolle Enzyme in den Metagenomdaten für aktuelle und zukünftige Anwendungen klassifiziert und quantifiziert. Da Biofilme bakterielle Virulenz verstärken und die Empfindlichkeit gegenüber antibakteriellen Substanzen verringern scheint nur ein breitgefächerter Ansatz erfolgsversprechend, um entweder die Biofilmarchitektur aufzubrechen und klassischen Antibiotika den Zugang zu den Bakterien zu erleichtern oder um den Prozess der Biofilmformation zu schwächen, im besten Falle sogar zu unterbinden. Die Metagenomdaten sollten daher als Werkzeugkasten dienen, Schlüsselstellen in der Biofilmbildung wie das Quorum Sensing, die initiale Anheftung oder die Anreicherung von EPS (extracellular polymeric substances) anzugreifen. Ein besonderes Augenmerk sollte auf die Rolle der extrazellulären DNA gerichtet werden. Erste Erfahrungen mit einem Enzym, das auf Grundlage eines Mikroalgenmetagenoms entwickelt wurde, konnten mit einer Dienlacton Hydrolase (Dlh3) gewonnen werden, die
wahrscheinlich im Sinne des Quorum Quenchings wirkt. Im Hinblick auf deren Anwendbarkeit im Aquakultur-Sektor wurde Dlh3 an den Fischpathogenen Edwardsiella anguillarum, Aeromonas salmonicida, P. aeruginosa, Flavobacterium columnare und Flavobacterium psychrophilum erprobt. Die Wirkung der Dlh3 auf die Fischpathogene wurde in statischen Anti-Biofilm-Assays, LSCM und dem oCelloScope getestet. Um bis zu 54.4% konnte die Biofilmbildung z.B. in E. anguillarum reduziert werden, einhergehend mit Veränderungen der Biofilmarchitektur, die in den optischen Verfahren deutlich wurden. Ermutigt durch die gewonnenen Erkenntnisse, wurden weitere zielgerichtete Enzyme in den neu etablierten Metagenomdaten der Mikroalgen-Bakterien-Gemeinschaften gesucht. Die erfolgreich überexprimierten Enzyme, eine Methylcytosin-spezifische Restriktionsendonuclease, die DNA an spezifisch modifizierten Basen schneidet, eine 8-Oxoguanin Deaminase, die extrazelluläre DNA modifiziert und eine zweite Dienlacton Hydrolase wurden phylogenetisch und strukturell charakterisiert. Erste Anwendungen der Enzyme auf Fischpathogenen zeigten deutliche Effekte auf die Überlebensfähigkeit der bakteriellen Zellen im Biofilm und auf die Strukturen der Biofilme im LSCM. In Anbetracht der Unschädlichkeit der untersuchten Enzyme für eukaryotische Zellen, die in Toxizitätstests bewiesen wurde, könnte diese Studie ein wegweisender Ansatz für einen vielfältigen Angriff auf bakterielle Biofilme sein, der die Gefahr der Resistenz vermindert und gleichzeitig, durch den Charakter eines variablen Werkzeugkastens die Flexibilität erhält, auf wechselnde Bedürfnisse zu reagieren, wie sie in Tierzucht mit hoher Dichte, wie der Aquakultur, zu erwarten sind
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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