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The effect of rhamnolipid production on Pseudomonas aeruginosa physiology
No full textPseudomonas aeruginosa is a notorious human pathogen associated with a range of lifethreatening nosocomial infections. P. aeruginosa is known to produce a range of virulence factors that enhance its ability to damage the host tissue and cause disease. One of the most important virulent-related molecules is rhamnolipid. The rhamnolipids are known in P. aeruginosa as a multifunctional surfactant. Identifying the functions of rhamnolipids in detail is clearly warranted to elucidate of the mechanisms of P. aeruginosa pathogenesis and to explore new strategies for treatment. P. aeruginosa regulates rhamnolipid production by using an intercellular communication mechanism called quorum sensing, which is mediated by small signaling molecules, or auto-inducers. In the present study, two rhamnolipid mutants were constructed and their physiological functions on P. aeruginosa were investigated under Pi depletion conditions. In this study, the surface-associated GroEL protein, which can be a host-pathogen interaction and anti-biofilm target, promoted early biofilm formation in P. aeruginosa. Pi depletion is known to rapidly develop following major surgery and organ injury and independently predicts the development of lethal sepsis (261),(106). The QSSM profile identification study for rhamnolipid-deficient mutants revealed high PQS and C4-HSL levels that significantly impact several virulence-associated phenotypes, such as Pvds-regulated endoprotease, lipase and phospholipase production, which was confirmed by extracellular proteomic and phenotypic analyses. However, similar phenotypic characteristics for a mono-rhamnolipid-producing strain and wild type PAO1 were obtained. The non-swarming and flat biofilm forming phenotype of the ∆rhlA strain suggested an altered outer membrane protein profile, which was verified by proteomic analyses. Furthermore, the GroEL protein was detected at different expression levels in a rhamnolipid-deficient mutant compared to wild type PAO1. This result led to the question of whether GroEL has an additional function, and GroEL was successfully overexpressed in a rhamnolipid-deficient mutant for subsequent functional characterization. The higher expression level of extracellular surface-associated GroEL protein was confirmed by extracellular and cytoplasmic proteome analyses. The suggested role was shown by crystal violet assay and the control of cell lysis was confirmed by β-lactamase activity assay and LipH Western blotting analyses. The presented data in this study is the first report of a proteome-based study of rhamnolipid mutants and the surface-associated GroEL and its new role in P. aeruginosa. Moreover, these results indicate anti-biofilm targets in P. aeruginosa.Pseudomonas aeruginosa ist ein berüchtigter menschlicher Krankheitserreger im Zusammenhang mit lebensbedrohlichen nosocomial-Infektionen. P. aeruginosa ist bekannt, eine Reihe von Virulenzfaktoren zu produzieren, die seine Fähigkeit verbessern, das Wirtsgewebe zu beschädigen und Krankheit zu verursachen. Eine der wichtigsten Virulenzbezogenen Moleküle sind Rhamnolipide. Die Rhamnolipide in P. aeruginosa sind bekannt dafür, multifunktionale oberflächenaktive Stoffe zu sein. Die Identifizierung der Funktionen von Rhamnolipiden im Detail, ist von vorrangiger Wichtigikeit, um die Pathogenese von P. aeruginosa zu verstehen und neue Strategien für die Behandlung zu finden. P. aeruginosa reguliert die Produktion von Rhamnolipiden mittels eines Kommunikationsmechanismus, auch Quorum Sensing genannt, bei dem kleine Signalmoleküle oder Autoinduktoren Informationen zwischen den Zellen vermitteln. In der vorliegenden Studie wurden zwei Rhamnolipid-Mutanten kreiert und ihre physiologische Wirkung auf P. aeruginosa wurde unter Phosphat (Pi)-Mangel untersucht. In dieser Studie förderte das an der Zelloberfläche vorkommende Eiweiß GroEL, das ein Ziel für eine Wirt-Krankheitserreger-Interaktion und ein Ziel für Biofilminhibitoren sein kann, eine frühe Ausformung an Biofilm in P. aeruginosa. Es ist bekannt, dass Pi-Mangel sich rasch nach größeren Operations- und Organverletzung entwickelt, und dass er die Entwicklung tödlicher Sepsis unabhängig vorhersagen kann (261), (106). Die QSSM Profilidentifikationsstudie für Mutanten, die keine Rhamnolipide mehr herstellen, offenbarte hohe Werte an PQS und C4-HSL, die mehrere virulenzzugehörige Phänotypen wie Pvds-regulierte Endoprotease-, Lipase- und Phospholipaseproduktion beeinflussen. Dies wurde mittels Analyse des extrazellulären Proteoms und des Phänotyps bestätigt. Es wurden jedoch ähnliche phänotypische Merkmale zwischen einem Stamm, der nur ein Mono-Rhamnolipid produziert, und dem Wild Typ PAO1 festgestellt. Der Phänotyp des ∆rhlA-Stammes, der nicht schwärmt und einen flachen Biofilm formt, weist auf ein geändertes Profil der Eiweißzusammensetzung hin; dies wurde mittels Analyse des Proteoms überprüft. Desweiteren zeigte das GroEL-Eiweiß ein anderes Expressionsniveau in einer Rhamnolipid-Mutante verglichen mit dem Wildtyp PAO1. Dieses Ergebnis führte zur Frage, ob GroEL eine zusätzliche Funktion hat und GroEL wurde erfolgreich in der Rhamnolipid-Mutante überexpremiert für eine anschließende funktionelle Charakterisierung. Das höhere Expressionsniveau des extrazellulären oberflächenzugehörigen GroEL-Eiweißes wurde mittels extrazellulären und zytoplasmatischen Proteom-Analysen bestätigt. Die vorgeschlagene Rolle für GroEL wurde mittels eines Krystallviolettetest bestätigt, wobei die Zellyse mittels einer β-Lactamase Aktivitätsprüfung und eines Western Blots gegen LipH kontrolliert wurde. Die in dieser Studie gezeigten Daten sind der erste Bericht über eine Proteom-basierte Studie über Rhamnolipid-Mutanten und das oberflächenzugehörige GroEL und seine neue Rolle in P. aeruginosa. Außerdem weisen diese Ergebnisse auf Ziele für Biofilminhibitoren in P. aeruginosa hin
The Effect of Phosphate Limitation on Rhamnolipid Production and Related Quorum Sensing Signal Molecules in Pseudomonas aeruginosa
No full textIntroduction: Rhamnolipid (RL) is one of the virulence factor secreted from Pseudomonas aeruginosa and is required to establish and persist the infection. The control of RL production is under control of Quorum Sensing System, and it is influenced by numerous factors of environmental/nutritional levels. In this study, it was aimed to investigated the phosphate depletion effect on selected Quorum Sensing Signal Molecules (QSSMs) under condition of rhamnolipid production. Materials and Methods: The effect of phosphate on RL production was examined in P. aeruginosa PAO1 and RL mutant strains by Orcinol and TLC plate test. Additionally, HPLC/MS quantification for QSSMs related to rhamnolipid production was carried out using the samples isolated from 16, 24 and 48 h cultures grown in Luria-Bertani (LB) and Proteose Peptone Glucose Amonium Salt (PPGAS) medium. Results: The increase in rhamnolipid production in PPGAS medium, for the wild type strain (48 h) amounted up to 20 fold was achieved compared to LB media by Orcinol assay. The cultures from PPGAS medium supplemented with 50 mM phosphate displayed significantly lower amount of rhamnolipid in 48 and 72 h cultures by 54% and 64%, respectively. The highest concentration of QSSMs were the C4-HSL and PQS for all strains. Then, the QSSM profile was followed by 3-oxo-C12-HSL and HHQ. Conclusion: Phosphate limitation increased rhamnolipid production via RhlR and PQS systems in P. aeruginosa PAO1. Considering the fact that other virulence factors are activated while rhamnolipid production is increased, phosphate limitation leads to an increase in the virulence of P. aeruginosa
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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