WorldWideScience

Sample records for biofilme mit mischkulturen

  1. Advanced waste water cleaning with the aid of an algae biofilm; Weitergehende Abwasserreinigung mit Hilfe eines Algenbiofilms

    Energy Technology Data Exchange (ETDEWEB)

    Schumacher, G.; Patzold, V.; Ike, A.; Sekoulov, I. [Technische Univ. Hamburg-Harburg, Hamburg (Germany). Arbeitsbereich Abwasserwirtschaft

    1999-07-01

    These first investigations have led to results indicating that advanced waste water cleaning with the aid of algae biofilm as a downstream process stage is feasible. The concentration of phosphorus in waste water could be reduced to less than 1 mg per litre. Ammonium, which is toxic to fish, was nitrified, and the overall nitrogen concentration could be cut down. The concentration of bacteria was reduced by means of a close-to-nature process to less than the limiting values set by the European Union directive governing the quality of bathing waters. (orig.) [German] Die Ergebnisse dieser ersten Untersuchungen zeigen, dass eine weitergehende Abwasserreinigung mit Hilfe eines Algenbiofilms als nachgeschaltete Verfahrensstufe moeglich ist. Die Phosphorkonzentration im Abwasser konnte auf unter 1 mg/l reduziert werden. Fischgiftiges Ammonium wurde nitrifiziert und die Gesamtstickstoffkonzentration konnte gesenkt werden. Die Bakterienkonzentration konnte mit Hilfe eines naturnahen Verfahrens bis unter die Grenzwerte der EU-Richtlinie ueber die Qualitaet der Badegewaesser reduziert werden. (orig.)

  2. Interactions of uranium (VI) with biofilms; Wechselwirkung von Uran(VI) mit Biofilmen

    Energy Technology Data Exchange (ETDEWEB)

    Brockmann, Sina; Arnold, Thuro; Bernhard, Gert

    2013-07-01

    In this study a detailed investigation was made of natural biofilms from two uranium-contaminated sites, namely the former uranium mine in Koenigstein (Saxony) and the ground surface of the former Grassenhalde tailing heap in Thuringia. A predominance of uranyl sulphate (UO{sub 2}SO{sub 4}), a highly mobile, solute uranium species, was found in the mine waters of both sites. In this study an investigation was made of the capacity of Euglena mutabilis cells for bioaccumulation of uranium in a pH range of 3 to 6 using living cells and sodium perchlorate (9 g/l) or sodium sulphate (3.48 g/l) as background media. At acidic pH values in the range from 3 to 4 it was possible to remove more than 90% of the original uranium content from the test solution regardless of the medium being used. The speciation of the uranium accumulated in the Euglena cells was investigated by laser-induced fluorescence spectroscopy (LIFS). It was found that a new uranium species of low variability forms on the cells independent of the background medium, state of life of the cells and pH value. By comparing the data from the LIFS measurements with reference values it was possible to narrow down the identity of the uranium species to one bonded to (organo) phosphate and/or carboxylic functional groups. Using time-resolved FT-IR spectroscopy it was possible to demonstrate carboxylic bonding of uranium to dead cells. However it was not possible to exclude (organo) complexation with this method. An investigation of the specific location of the uranium on or in the cells using combined CLSM/LIFS technology yielded first indications of intracellular accumulation of uranium in the living cells. Supplementary TEM/EDX measurements confirmed the intracellular uptake, showing it to occur in round to oval cell organelles which are thought to be vacuoles or vacuole-like vesicles. It was not possible to detect uranium on dead cells using these methods. This points to passive, homogeneously distributed

  3. Biofilms

    OpenAIRE

    López, Daniel; Vlamakis, Hera; Kolter, Roberto

    2010-01-01

    The ability to form biofilms is a universal attribute of bacteria. Biofilms are multicellular communities held together by a self-produced extracellular matrix. The mechanisms that different bacteria employ to form biofilms vary, frequently depending on environmental conditions and specific strain attributes. In this review, we emphasize four well-studied model systems to give an overview of how several organisms form biofilms: Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and ...

  4. Mit kokkeri

    DEFF Research Database (Denmark)

    Ejlersen, Søren; Lorang, Louisa

    MIT kokkeri er resultatet af et samarbejde mellem Komiteen for Sundhedsoplysning, Institut for Uddannelse og Pædagogik/Aarhus Universitet og Haver til Maver. Projektet støttes af Nordea-fonden. Bag kogebogens mange opskrifter står en række erfarne madeksperter bestående af Søren Ejlersen, Louisa ...

  5. Combating biofilms

    DEFF Research Database (Denmark)

    Yang, Liang; Liu, Yang; Wu, Hong;

    2012-01-01

    Biofilms are complex microbial communities consisting of microcolonies embedded in a matrix of self-produced polymer substances. Biofilm cells show much greater resistance to environmental challenges including antimicrobial agents than their free-living counterparts. The biofilm mode of life...... is believed to significantly contribute to successful microbial survival in hostile environments. Conventional treatment, disinfection and cleaning strategies do not proficiently deal with biofilm-related problems, such as persistent infections and contamination of food production facilities. In this review......, strategies to control biofilms are discussed, including those of inhibition of microbial attachment, interference of biofilm structure development and differentiation, killing of biofilm cells and induction of biofilm dispersion....

  6. MITS machine operations

    International Nuclear Information System (INIS)

    This document contains procedures which apply to operations performed on individual P-1c machines in the Machine Interface Test System (MITS) at AiResearch Manufacturing Company's Torrance, California Facility

  7. Investigation of mass transfer phenomena in biofilm systems; Untersuchung von Stoffuebergangsphaenomenen in Biofilmsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Waesche, S.; Hempel, D.C. [Technische Univ. Braunschweig (Germany). Inst. fuer Bioverfahrenstechnik; Horn, H. [Fachhochschule Magdeburg (Germany). Hydro- und Abfallchemie

    1999-07-01

    Substance transfer in the boundary layer bulk/biofilm can be only inadequately described by conventional model concepts. In such cases where the surface structure of a biofilm adapts to given hydraulic conditions, the substance transfer phenomena need to be studied in depth. In addition, the entire biofilm structure is much influenced both by substrate conditions and by hydrodynamic conditions during growth. With a view to quantifying these factors, biofilms were cultured under various substrate and hydrodynamic conditions in tube reactors with a diameter of 2.6 cm. For characterizing the cultured biofilms, biofilm density and substrate turnover measured as maximum mass transfer density were determined in each test series. Biofilm density (dry biomass/biofilm volume) was determined by gravimetry. Maximum mass transfer densities in biofilm were established in batch experiments with excess substrate. By means of oxygen microelectrodes, oxygen profiles in the biofilm were measured directly in the reactor. These measurements concerned biofilms of thicknesses ranging from 400 to 2000 {mu}m, where the biofilms did not yet exhibit erosion. (orig.) [German] Der Stoffuebergang in der Grenzschicht Bulk/Biofilm ist mit herkoemmlichen Modellvorstellungen nur ungenuegend beschreibbar. Eine sich an die aktuellen hydraulischen Bedingungen anpassende Oberflaechenstruktur des Biofilms erfordert eine intensive Untersuchung der Stoffuebergangsphaenomene in derartigen Systemen. Darueber hinaus wird die gesamte Biofilmstruktur sowohl von den Substratbedingungen als auch von den hydrodynamischen Bedingungen waehrend des Wachstums stark beeinflusst. Um diese Faktoren quantifizieren zu koennen, wurden Biofilme bei verschiedenen Substrat- und hydrodynamischen Bedingungen in Rohrreaktoren mit einem Durchmesser von 2,6 cm kultiviert. Zur Charakterisierung der kultivierten Biofilme wurde die Biofilmdichte und der Substratumsatz, gemessen als maximale Massestromdichte, bei jeder Versuchsreihe

  8. Permeabilizing biofilms

    Science.gov (United States)

    Soukos, Nikolaos S.; Lee, Shun; Doukas, Apostolos G.

    2008-02-19

    Methods for permeabilizing biofilms using stress waves are described. The methods involve applying one or more stress waves to a biofilm, e.g., on a surface of a device or food item, or on a tissue surface in a patient, and then inducing stress waves to create transient increases in the permeability of the biofilm. The increased permeability facilitates delivery of compounds, such as antimicrobial or therapeutic agents into and through the biofilm.

  9. Beneficial biofilms

    Directory of Open Access Journals (Sweden)

    Sara R Robertson

    2015-10-01

    Full Text Available Surface-adherent biofilm growth is a common trait of bacteria and other microorganisms in nature. Within biofilms, organisms are present in high density and are enmeshed in an organic matrix containing polysaccharides and other molecules. The close proximity of organisms within biofilms facilitates microbial interactions and signaling, including many metabolic processes in which consortia rather than individual organisms participate. Biofilm growth also enables microorganisms to withstand chemical and biological stresses. Here, we review some current literature and document representative beneficial aspects of biofilms using examples from wastewater treatment, microbial fuel cells, biological repair (biocementation of stonework, and biofilm protection against Candida albicans infections. Finally, we address a chemical ecology strategy whereby desired microbial succession and beneficial biofilm formation can be encouraged via manipulation of culture conditions and bacterial signaling.

  10. Organische Leuchtdioden mit Polymeranoden

    OpenAIRE

    Fehse, Karsten

    2008-01-01

    In organischen Leuchtdioden (OLEDs) werden üblicherweise anorganische Materialien wie Indium-Zinn-Oxid (ITO) als transparente leitfähige Anoden verwendet. ITO besitzt allerdings eine geringe Austrittsarbeit und kann deshalb Löcher nicht effizient in organische Materialien injizieren. Weiterhin ist ITO eine Quelle von Indium- und Sauerstoff-Ionen, die in die organischen Materialien diffundieren und dort mit der Organik reagieren bzw. als effiziente Exzitonenvernichter agieren. Eine mögliche Al...

  11. Marketing mit Facebook

    OpenAIRE

    Nufer, Gerd; Vogt, Maximilian

    2013-01-01

    Die Integration von Facebook in ein bestehendes Marketingkonzept avanciert zunehmend zum Erfolgsfaktor innovativer Unternehmen. Das Marketing mit diesem sozialen Netzwerk ist dabei nicht auf die Kommunikationspolitik determiniert, sondern bietet die Möglichkeit, einen nachhaltigen Mehrwert im gesamten Marketing-Mix zu generieren. Vor diesem Hintergrund stellt Facebook aktuell das meist eingesetzte Social Marketing Instrument in Deutschland dar. Im Kontrast zum steigenden Bewusstsein der Vorte...

  12. Salmonella biofilms

    NARCIS (Netherlands)

    Castelijn, G.A.A.

    2013-01-01

    Biofilm formation by Salmonellaspp. is a problem in the food industry, since biofilms may act as a persistent source of product contamination. Therefore the aim of this study was to obtain more insight in the processes involved and the factors contributing to Salmonellabiofilm formation. A collectio

  13. Medical Biofilms

    OpenAIRE

    Bryers, James D.

    2008-01-01

    For more than two decades, Biotechnology and Bioengineering has documented research focused on natural and engineered microbial biofilms within aquatic and subterranean ecosystems, wastewater and waste-gas treatment systems, marine vessels and structures, and industrial bioprocesses. Compared to suspended culture systems, intentionally engineered biofilms are heterogeneous reaction systems that can increase reactor productivity, system stability, and provide inherent cell: product separation....

  14. Biofilm Infections

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Jensen, Peter Østrup; Moser, Claus Ernst;

    such as diagnostics, pathogenesis, treatment regimes and in vitro and in vivo models for studying biofilms. This is the first scientific book on biofilm infections, chapters written by the world leading scientist and clinicians. The intended audience of this book is scientists, teachers at university level as well...... as being important in chronic infection. In 1993 the American Society for Microbiology (ASM) recognized that the biofilm mode of growth was relevant to microbiology. This book covers both the evidence for biofilms in many chronic bacterial infections as well as the problems facing these infections......, especially the central role of aggregating bacteria in chronic infections. He has a combined position at University of Copenhagen and Copenhagen University Hospital. Due to this Thomas has both a scientific and applied approach to the role of biofilms in chronic infections. This has also been his approach...

  15. Ammoniakzersetzung mit salzmodifizierten Katalysatoren

    OpenAIRE

    Bajus, Stephanie

    2014-01-01

    Ziel dieser Arbeit war es, durch die Modifikation von Rutheniumkatalysatoren mit Salzen ein aktives System für die Ammoniakzersetzung zur Wasserstofffreisetzung zwischen 200 °C und 350 °C zu entwickeln. Die Modifikation sollte auf dem SCILL-Konzept aufbauen, bei dem in der ursprünglichen Variante eine ionische Flüssigkeit geträgert auf einem heterogenen Katalysator die katalytische Oberfläche modifizieren soll. Da ionische Flüssigkeiten nur bedingt thermisch stabil sind, sollte dieses Konzept...

  16. Biofilm Development

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim

    2015-01-01

    During the past decade we have gained much knowledge about the molecular mechanisms that are involved in initiation and termination of biofilm formation. In many bacteria, these processes appear to occur in response to specific environmental cues and result in, respectively, induction or terminat......During the past decade we have gained much knowledge about the molecular mechanisms that are involved in initiation and termination of biofilm formation. In many bacteria, these processes appear to occur in response to specific environmental cues and result in, respectively, induction...... or termination of biofilm matrix production via the second messenger molecule c-di-GMP. In between initiation and termination of biofilm formation we have defined specific biofilm stages, but the currently available evidence suggests that these transitions are mainly governed by adaptive responses......, and not by specific genetic programs. It appears that biofilm formation can occur through multiple pathways and that the spatial structure of the biofilms is species dependent as well as dependent on environmental conditions. Bacterial subpopulations, e.g., motile and nonmotile subpopulations, can develop...

  17. Wound biofilms: lessons learned from oral biofilms

    OpenAIRE

    Mancl, Kimberly A.; Kirsner, Robert S.; Ajdic, Dragana

    2013-01-01

    Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque,are a primary cause of oral diseases including caries, gingivitis and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible, thus biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well-elucidated. In contrast, wound research has relati...

  18. Wound biofilms: lessons learned from oral biofilms.

    Science.gov (United States)

    Mancl, Kimberly A; Kirsner, Robert S; Ajdic, Dragana

    2013-01-01

    Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

  19. Die Last mit der Lust

    Directory of Open Access Journals (Sweden)

    Lutz Sauerteig

    2004-03-01

    Full Text Available Robert Jütte legt mit Lust ohne Last eine umfassende, allgemeinverständliche und spannend zu lesende Geschichte der Empfängnisverhütung von der Antike bis in die unmittelbare Gegenwart vor.

  20. MIT-CSR XIS Project

    Science.gov (United States)

    1998-01-01

    This report outlines the proposers' progress toward MIT's contribution to the X-Ray Imaging Spectrometer (XIS) experiment on the Japanese ASTRO-E mission. The report discusses electrical system design, mechanical system design, and ground support equipment.

  1. Verbalsuffixe mit Liquida

    Directory of Open Access Journals (Sweden)

    Marina Zorman

    1995-12-01

    Full Text Available Der vorliegende Beitrag stellt eine Zusammenfassung bzw. vervollständigte Ver­ sion einiger Kapitel der Magisterarbeit der Autorin mit dem Titel Expressive Wort­ bildung beim Verb (Ältere, wahrscheinlich ererbte Kombinationen -V/C- + -r/l- - das Grundtypus -dr- - im Slowenischen dar. Die wesentlichen Erkenntnisse der Arbeit hinsichtlich der morphologischen und semantischen Gestalt derartiger Verben, ihrer dialektologischen Verbreitung und der Genese, Funktion und Austauschbarkeit dieser Suffixe sollen unter dem Titel "Ekspresivne glagolske pripone tipa -V/C + -r/l-" in den "Razprave XV II. razreda SAZU" (Dissertationes Classis II, XV. Ljubljana, Academia scientiarium et artium Slovenica (in Druck veröffentlicht werden, deshalb werden sie hier nur so weit aufgenommen, wie das für das Verständnis des behandelten Gegen­ stands unbedingt notwendig ist. Eingehender werden Fragen erortert, die im erwähnten Artikel nicht behandelt werden, die jedoch auch für andere Linguisten interessant sein könnten. So ist der vorliegende Beitrag in vier Teile gegliedert

  2. Rezidivmuster bei Kindern mit Medulloblastom

    OpenAIRE

    Blaßhofer, Sophia Katharina Charlotte

    2009-01-01

    Ziel der vorliegenden Arbeit ist es, das Rezidivmuster der Medulloblastome aufzuzeigen. Die Bedeutung prognostischer Faktoren, wie Therapie oder initiale Erkrankungsausdehnung soll im Zusammenhang mit dem Auftreten eines Rezidivs oder einer Progression näher untersucht werden. Es handelt sich um ein Patientenkollektiv von 40 Kindern mit einem Rezidiv eines Medulloblastoms. Die Patienten sind Teil des HIT 2000 Kollektivs, ein Patient war Teil der HIT ´91 Studie, 7 waren Beobachtungspatienten. ...

  3. Bacterial biofilms. Bacteria Quorum sensing in biofilms

    OpenAIRE

    E. S. Vorobey; O. S. Voronkova; A. I. Vinnikov

    2012-01-01

    Data on biofilms, their structure and properties, peculiarities of formation and interaction between microorganisms in the film are presented. Information on discovery and study of biofilms, importance of biofilms in the medical and clinical microbiology are offered. The data allow to interpret biofilm as a form of existence of human normal microflora. For the exchange of information within the biofilm between the individual cells of the same or different species bacteria use the signal molec...

  4. MIT's interferometer CST testbed

    Science.gov (United States)

    Hyde, Tupper; Kim, Ed; Anderson, Eric; Blackwood, Gary; Lublin, Leonard

    1990-12-01

    The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances.

  5. Google Books - Abzocken mit Rechtsbeistand

    OpenAIRE

    Gerhard Ruiss

    2010-01-01

    Wie sieht es eigentlich mit den Rechten bei "Google Books" aus? Vor rund einem Jahr wurden zum ersten Mal die Pläne von Google zur Veröffentlichung aller jemals erschienenen Bücher auf der Internetplattform "Google Book Search" bzw. mittlerweile "Google Bücher" auch außerhalb der USA bekannt. Bis zu diesem Zeitpunkt hielt man in den meisten anderen Ländern den Konflikt amerikanischer Autoren und Verlage mit dem US-Netzdienstleister "Google" über die Veröffentlichungsrechte für einen inner...

  6. Erfahrungen mit einem C-Pen

    OpenAIRE

    Ziegler, Christoph

    2002-01-01

    Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. Der Vortrag beginnt mit der Vorstellung eines C-Pen. Erfahrungen mit der praktischen Anwendung eines solchen "Computer-Stiftes" bilden den Hauptteil.

  7. The AdMit Package

    NARCIS (Netherlands)

    D. David (David); L.F. Hoogerheide (Lennart); H.K. van Dijk (Herman)

    2008-01-01

    textabstractThis short note presents the R package AdMit which provides flexible functions to approximate a certain target distribution and it provides an efficient sample of random draws from it, given only a kernel of the target density function. The estimation procedure is fully automatic and thu

  8. Game Design Workshops mit Schulklassen

    OpenAIRE

    Christoph Kaindel

    2015-01-01

    Im Oktober 2015 hat Christoph Kaindel gemeinsam mit Claudia Bayerl fünf Game Design Workshops in der wienXtra spielebox durchgeführt. Dabei haben Schulklassen der 3. bis 8. Schulstufe teilgenommen, die Gruppengrößen lagen zwischen 17 und 24. Der Projektleiter berichtet ...

  9. Game Design Workshops mit Schulklassen

    Directory of Open Access Journals (Sweden)

    Christoph Kaindel

    2015-12-01

    Full Text Available Im Oktober 2015 hat Christoph Kaindel gemeinsam mit Claudia Bayerl fünf Game Design Workshops in der wienXtra spielebox durchgeführt. Dabei haben Schulklassen der 3. bis 8. Schulstufe teilgenommen, die Gruppengrößen lagen zwischen 17 und 24. Der Projektleiter berichtet ...

  10. The Biofilm Challenge

    DEFF Research Database (Denmark)

    Alhede, Maria; Alhede, Morten

    2014-01-01

    reveals the significance of biofilms, as evidenced by a dramatic increase in scientific publications on the topic, as well as in publications concerning wounds with biofilms, which reached 600 publications in 2013. Judged from the number of publications, it appears that biofilms play a significant role...... in wounds. However, the impact of biofilms is often debated, because infected wounds were also treated before the concept of biofilms was coined. In this short review, we will address the significance of biofilms and their role in wounds, and discuss the future tasks of the biofilm challenge....

  11. The in vivo biofilm

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Alhede, Maria; Alhede, Morten;

    2013-01-01

    Bacteria can grow and proliferate either as single, independent cells or organized in aggregates commonly referred to as biofilms. When bacteria succeed in forming a biofilm within the human host, the infection often becomes very resistant to treatment and can develop into a chronic state. Biofilms...... have been studied for decades using various in vitro models, but it remains debatable whether such in vitro biofilms actually resemble in vivo biofilms in chronic infections. In vivo biofilms share several structural characteristics that differ from most in vitro biofilms. Additionally, the in vivo...... experimental time span and presence of host defenses differ from chronic infections and the chemical microenvironment of both in vivo and in vitro biofilms is seldom taken into account. In this review, we discuss why the current in vitro models of biofilms might be limited for describing infectious biofilms...

  12. Tragverhalten von Textilbeton mit Kurzfasern

    OpenAIRE

    Brameshuber, Wolfgang; Hinzen, Marcus

    2011-01-01

    Das Tragverhalten von Textilbeton kann durch den Einsatz von Kurzfasern erheblich verbessert werden. Untersuchungen zeigen eine Anhebung der Erstrisslast, ein dehnungsverfestigendes Verhalten, eine Verfeinerung des Rissbildes sowie eine Anhebung der maximalen Tragfähigkeit. Unklar sind bisher noch die genauen Mechanismen, die eine gezielte Einstellung des Tragverhaltens ermöglichen. Der Beitrag fasst die Untersuchungen zu den einzelnen Bereichen der Spannungs- ehnungslinie von Textilbeton mit...

  13. Befestigungen mit Verbundankern. Teil 3

    OpenAIRE

    Eligehausen, Rolf; Mallée, Rainer; Rehm, Gallus

    1984-01-01

    Seit 1975 wurden Verbundankersysteme verschiedener Firmen bauaufsichtlich zugelassen, wobei die Systeme hinsichtlich der Zusammensetzung des Mörtels praktisch identisch sind. Diese Zulassungsbescheide regelten die Verwendung von Einzelankern sowie Ankerpaaren mit Ankern in der aus Lastspannungen erzeugten Druckzone von Beton- und Stahlbetonbauteilen. Die Anwendungsbedingungen wurden u. a. aus den beschriebenen Versuchen abgeleitet und sind ausführlich erläutert. Weitere wichtige Informationen...

  14. Befestigungen mit Verbundankern. Teil 2

    OpenAIRE

    Eligehausen, Rolf; Mallée, Rainer; Rehm, Gallus

    1984-01-01

    Seit 1975 wurden Verbundankersysteme verschiedener Firmen bauaufsichtlich zugelassen, wobei die Systeme hinsichtlich der Zusammensetzung des Mörtels praktisch identisch sind. Diese Zulassungsbescheide regelten die Verwendung von Einzelankern sowie Ankerpaaren mit Ankern in der aus Lastspannungen erzeugten Druckzone von Beton- und Stahlbetonbauteilen. Die Anwendungsbedingungen wurden u. a. aus den beschriebenen Versuchen abgeleitet und sind ausführlich erläutert. Weitere wichtige Informationen...

  15. Befestigungen mit Verbundankern. [Teil 1

    OpenAIRE

    Eligehausen, Rolf; Mallée, Rainer; Rehm, Gallus

    1984-01-01

    Seit 1975 wurden Verbundankersysteme verschiedener Firmen bauaufsichtlich zugelassen, wobei die Systeme hinsichtlich der Zusammensetzung des Mörtels praktisch identisch sind. Diese Zulassungsbescheide regelten die Verwendung von Einzelankern sowie Ankerpaaren mit Ankern in der aus Lastspannungen erzeugten Druckzone von Beton- und Stahlbetonbauteilen. Die Anwendungsbedingungen wurden u. a. aus den beschriebenen Versuchen abgeleitet und sind ausführlich erläutert. Weitere wichtige Informationen...

  16. Relazione tecnica su DSpace (MIT)

    OpenAIRE

    De Robbio, Antonella

    2002-01-01

    This report presents Dspace that is a product realized in 2000 between Libraries of MIT (Massachussetts Institute Technology) and Hewlett-Packard Company relating to building a repository. It is able to support long-term memory, capturing and archiving of scholastic documents, realized from all MIT’s departments and free access by WWW, too. Furthermore, Dspace supports distribution and self-preservation of a different kinds of materials such as texts, videos, sounds, pictures, software and...

  17. MitWirkung - Zukunft gestalten

    OpenAIRE

    Säck-da Silva, Sabine

    2009-01-01

    Die Diskussion in den Planungswissenschaften beschreibt den Paradigmenwechsel vom so genannten DEAD-Model (Decide-Announce-Defend) zum Tripple-D-Model (Dialogue-Decide-Deliver) und beschäftigt sich intensiv mit dem Thema Governance. Komplexe Planungsaufgaben brauchen eine Vielfalt an Lösungsideen unterschiedlicher gesellschaftlicher Gruppen. Planung verfolgt u. a. die Umsetzung der Ziele einer nachhaltigen Entwicklung, die die Einbeziehung der Öffentlichkeit (Zivilgesellschaft, Unternehmen un...

  18. Google Books - Abzocken mit Rechtsbeistand

    Directory of Open Access Journals (Sweden)

    Gerhard Ruiss

    2010-03-01

    Full Text Available Wie sieht es eigentlich mit den Rechten bei "Google Books" aus? Vor rund einem Jahr wurden zum ersten Mal die Pläne von Google zur Veröffentlichung aller jemals erschienenen Bücher auf der Internetplattform "Google Book Search" bzw. mittlerweile "Google Bücher" auch außerhalb der USA bekannt. Bis zu diesem Zeitpunkt hielt man in den meisten anderen Ländern den Konflikt amerikanischer Autoren und Verlage mit dem US-Netzdienstleister "Google" über die Veröffentlichungsrechte für einen inneramerikanischen Streit. Erst durch die gerichtliche Anordnung des mit der Streitbeilegung beschäftigten New Yorker Richters Denny Chin zur weltweiten Bekanntmachung der konkreten Pläne von Google im Februar 2009 zeigte sich das gesamte Ausmaß der Absichten Googles. Google hatte in einem gerichtlichen Vergleichsdokument ("Google Book Settlement", das von Chin genehmigt werden sollte, sämtliche im Buchhandel erhältliche und in Bibliotheken archivierte Buchtitel weltweit aufgelistet, um sie nach gerichtlicher Genehmigung im Volltext in seinem Büchersuchdienst abrufbar zu machen. Inklusive weiterer Veröffentlichungen und Verbreitungen der Bücher zu seinem Nutzen und Gewinn wie u.a. durch Downloads, Print-On-Demand-Ausgaben, E-Books, Datenbank-Einspeisungen u.v.a.m.

  19. Biofilm Fixed Film Systems

    Directory of Open Access Journals (Sweden)

    Dipesh Das

    2011-09-01

    Full Text Available The work reviewed here was published between 2008 and 2010 and describes research that involved aerobic and anoxic biofilm treatment of water pollutants. Biofilm denitrification systems are covered when appropriate. References catalogued here are divided on the basis of fundamental research area or reactor types. Fundamental research into biofilms is presented in two sections, Biofilm Measurement and Characterization and Growth and Modeling. The reactor types covered are: trickling filters, rotating biological contactors, fluidized bed bioreactors, submerged bed biofilm reactors, biological granular activated carbon, membrane bioreactors, and immobilized cell reactors. Innovative reactors, not easily classified, are then presented, followed by a section on biofilms on sand, soil and sediment.

  20. Bioreactor plant for the reproducible building of biofilms; Bioreaktoranlage zur reproduzierbaren Bildung von Biofilmen

    Energy Technology Data Exchange (ETDEWEB)

    Scheen, J. [Dortmund Univ. (Germany). Inst. fuer Umweltforschung

    1998-10-01

    Biofilms frequently appear, they are sometimes useful and sometimes disturbing. For the investigation of biofilms, it was necessary to reproduce them in specific bioreactors. Furthermore, useful media and analytical methods have to define the influence of biocides and other substances. The gravimetric analysis of microbe-formed polysaccharides in water samples and biofilm makes it possible to recognise successful treatments. These conditions are described here. Using these instruments it was possible to build up reproducible biofilms, to test and optimise them in lab examinations. In view of the expected EU Biocide Directive, this process offers possibilities for searching and verifying the suitability of biocides and other substances. (orig.) [Deutsch] Biofilme treten vielfach, sowohl nuetzlich - als auch stoerend, auf. Fuer die Untersuchungen an Biofilmen wurde eine Bioreaktoranlage, ein synthetisches Medium und eine aussagekraeftige Analytik entwickelt. Mit der gravimetrischen Messung von mikrobiell gebildeten Exopolysacchariden, aus der waessrigen Phase und direkt aus dem Biofilm heraus, konnte die Bildung von Biofilmen verfolgt werden. Mit diesem Instrumentarium war es moeglich, Biofilme reproduzierbar zu bilden und die nuetzlichen als auch schaedlichen Eigenschaften von Biofilmen im Labor zu testen und zu optimieren. Dadurch koennen Foerder- als auch Vermeidungsmethoden durch z.B. Biozide oder andere Wirkstoffe besser beurteilt werden. Im Hinblick auf die zu erwartende EU-Biozid-Richtlinie bieten sich guenstige Untersuchungsmoeglichkeiten von Bioziden auf ihre Praxistauglichkeit an. (orig.)

  1. Vergleichende Untersuchungen zur Wasseraufbereitung mit getauchten Membranen

    OpenAIRE

    Seidel, Tosca

    2004-01-01

    Die vorliegende Ausgabe beschäftigt sich mit dem Thema vergleichende Untersuchungen zur Wasseraufbereitung mit getauchten Membranen. Es werden drei Verfahren zur Aufbereitung von Oberflächenwasser zu Trinkwasser unter technischen, ökonomischen und ökologischen Gesichtspunkten verglichen. Das Verfahren der Ultrafiltration mit getauchten Membranen wurde dazu für drei Monate in einem kleintechnischen Pilotversuch an der Aare, Schweiz, getestet und hinsichtlich der Filtrationsleistung unter Varia...

  2. Konzepte zur rekonstruktiven Bildgebung mit hochfrequentem Ultraschall

    OpenAIRE

    Opretzka, Jörn

    2011-01-01

    Diese Arbeit beschäftigt sich mit Verfahren, mit denen die Bildgebungseigenschaften hochfrequenter Ultraschall- Abbildungssysteme auf Basis sphärisch fokussierender Ultraschallwandler verbessert werden können. Bei der Technik des Limited Angle Spatial Compounding werden aus verschiedenen Blickwinkeln aufgenommene Echosignale nach Demodulation überlagert. Mittels der neuartigen Fokussierungstechnik PBF-SAFT werden die Echosignale zunächst mit dem Ziel einer tiefenunabhängigen Auflö...

  3. Pseudomonas aeruginosa Biofilm Infections

    DEFF Research Database (Denmark)

    Rybtke, Morten; Hultqvist, Louise Dahl; Givskov, Michael;

    2015-01-01

    Studies of biopsies from infectious sites, explanted tissue and medical devises have provided evidence that biofilms are the underlying cause of a variety of tissue-associated and implant-associated recalcitrant human infections. With a need for novel anti-biofilm treatment strategies, research...... in biofilm infection microbiology, biofilm formation mechanisms and biofilm-associated antimicrobial tolerance has become an important area in microbiology. Substantial knowledge about biofilm formation mechanisms, biofilm-associated antimicrobial tolerance and immune evasion mechanisms has been obtained...... through work with biofilms grown in in vitro experimental setups, and the relevance of this information in the context of chronic infections is being investigated by the use of animal models of infection. Because our current in vitro experimental setups and animal models have limitations, new advanced...

  4. Transacylierungen mit Acylderivaten des 4-Pyridons

    OpenAIRE

    Effenberger, Franz; Bessey, Eberhard

    1980-01-01

    Mit N-Acyl-4-pyridonen (2a, b) sowie mit 4-(Benzoyloxy)pyridin (3a) werden in Methylenchlorid oder Chloroform aliphatische und aromatische Amine sowie Thiole glatt zu den Amiden (4 - 6) und Thioestern (7, 8) acyliert. Primäre und sekundäre Alkohole reagieren langsamer, tert-Butylalkohol nur noch mit 3a unter Basenkatalyse sowie mit den reaktiveren N-(Trihalogenacetyl)-4-pyridonen 3b, c zu den tert-Butylestern 12. N-Acetyl-4-pyridon (2a) besitzt ein deutlich höheres Acylierungspotential als N-...

  5. Rheology of biofilms

    OpenAIRE

    Winston, M.; Rupp, C.J.; Vinogradov, A.; Towler, B.W.; Adams, H; Stoodley, P

    2003-01-01

    The paper describes an experimental study concerning the mechanical properties of bacterial biofilms formed from the early dental plaque colonizer Streptoccocus mutans and pond water biofilms. Experiments reported in this paper demonstrate that both types of biofilms exhibit mechanical behavior similar to that of rheological fluids. The time-dependent properties of both biofilms have been modeled using the principles of viscoelasticity theory. The Burger model has been found to accurately re...

  6. Pseudomonas aeruginosa biofilm infections

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim

    2014-01-01

    use of conventional antimicrobial compounds in many cases cannot eradicate biofilms, there is an urgent need to develop alternative measures to combat biofilm infections. The present review is focussed on the important opportunistic pathogen and biofilm model organism Pseudomonas aeruginosa. Initially...

  7. Biofilms: A microbial home

    OpenAIRE

    Chandki, Rita; Banthia, Priyank; Banthia, Ruchi

    2011-01-01

    Microbial biofilms are mainly implicated in etiopathogenesis of caries and periodontal disease. Owing to its properties, these pose great challenges. Continuous and regular disruption of these biofilms is imperative for prevention and management of oral diseases. This essay provides a detailed insight into properties, mechanisms of etiopathogenesis, detection and removal of these microbial biofilms.

  8. Desinfektion mit hydrodynamischer Kavitation und Chlordioxid

    OpenAIRE

    Maslak, Dominik

    2010-01-01

    Die Kombination von hydrodynamisch erzeugter Kavitation mit Desinfektionsmitteln ist ein neuer Ansatz zur effektiveren Wasserentkeimung. Zur Erzeugung oszillierender Kavitationsblasen wurde ein neuer Kavitationsreaktor (Mikrogitter mit Nachlaufdüse) entwickelt und reaktionstechnisch charakterisiert. Gegenüber der üblich verwendeten Lochblende wird hiermit besonders der Energieeintrag reduziert. Es konnte am Beispiel des Bakteriums Escherichia coli gezeigt werden, dass bei Kombination von hydr...

  9. Positive Werkzeuge mit hohem IQ

    Science.gov (United States)

    Luik, Matthias

    Fräsen ist ein Verfahren, auf welches im modernen Produktionsprozess nicht verzichtet werden kann. Dabei stellt die zunehmende Komplexität der zu fertigenden Bauteile ganz neue Herausforderungen an ein Werkzeug. Konnten früher Bauteile nur mit hohem Aufwand durch Erodieren oder Außenräumen hergestellt werden, müssen heute bereits Fräswerkzeuge für solche Bearbeitungsaufgaben aus Zeitund Kostengründen eingesetzt werden. Dies führt dazu, dass viele Bauteile heute in einer Aufspannung bearbeitbar sind, welche früher nur durch mehrmaliges Umspannen erzeugt werden konnten. Um Bearbeitungszeiten und -kosten dabei gering zu halten, müssen aber dennoch universelle Werkzeuge eingesetzt werden, welche für verschiedenste Bearbeitungsaufgaben ausgelegt sind.

  10. Pseudomonas aeruginosa biofilm infections

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim

    2014-01-01

    Bacteria in natural, industrial and clinical settings predominantly live in biofilms, i.e., sessile structured microbial communities encased in self-produced extracellular matrix material. One of the most important characteristics of microbial biofilms is that the resident bacteria display...... a remarkable increased tolerance toward antimicrobial attack. Biofilms formed by opportunistic pathogenic bacteria are involved in devastating persistent medical device-associated infections, and chronic infections in individuals who are immune-compromised or otherwise impaired in the host defense. Because...... the use of conventional antimicrobial compounds in many cases cannot eradicate biofilms, there is an urgent need to develop alternative measures to combat biofilm infections. The present review is focussed on the important opportunistic pathogen and biofilm model organism Pseudomonas aeruginosa. Initially...

  11. Osteocompatibility of Biofilm Inhibitors

    OpenAIRE

    Rawson, Monica; Haggard, Warren; Jennings, Jessica A.

    2014-01-01

    The demand for infection prevention therapies has led to the discovery of several biofilm inhibitors. These inhibiting signals are released by bacteria, fungi, or marine organisms to signal biofilm dispersal or disruption in Gram-positive, Gram-negative, and fungal microorganisms. The purpose of this study was to test the biocompatibility of five different naturally-produced biofilm chemical dispersal and inhibition signals with osteoblast-like cells: D-amino acids (D-AA), lysostaphin (LS), f...

  12. Host Responses to Biofilm.

    Science.gov (United States)

    Watters, C; Fleming, D; Bishop, D; Rumbaugh, K P

    2016-01-01

    From birth to death the human host immune system interacts with bacterial cells. Biofilms are communities of microbes embedded in matrices composed of extracellular polymeric substance (EPS), and have been implicated in both the healthy microbiome and disease states. The immune system recognizes many different bacterial patterns, molecules, and antigens, but these components can be camouflaged in the biofilm mode of growth. Instead, immune cells come into contact with components of the EPS matrix, a diverse, hydrated mixture of extracellular DNA (bacterial and host), proteins, polysaccharides, and lipids. As bacterial cells transition from planktonic to biofilm-associated they produce small molecules, which can increase inflammation, induce cell death, and even cause necrosis. To survive, invading bacteria must overcome the epithelial barrier, host microbiome, complement, and a variety of leukocytes. If bacteria can evade these initial cell populations they have an increased chance at surviving and causing ongoing disease in the host. Planktonic cells are readily cleared, but biofilms reduce the effectiveness of both polymorphonuclear neutrophils and macrophages. In addition, in the presence of these cells, biofilm formation is actively enhanced, and components of host immune cells are assimilated into the EPS matrix. While pathogenic biofilms contribute to states of chronic inflammation, probiotic Lactobacillus biofilms cause a negligible immune response and, in states of inflammation, exhibit robust antiinflammatory properties. These probiotic biofilms colonize and protect the gut and vagina, and have been implicated in improved healing of damaged skin. Overall, biofilms stimulate a unique immune response that we are only beginning to understand. PMID:27571696

  13. Dispersal from Microbial Biofilms.

    Science.gov (United States)

    Barraud, Nicolas; Kjelleberg, Staffan; Rice, Scott A

    2015-12-01

    One common feature of biofilm development is the active dispersal of cells from the mature biofilm, which completes the biofilm life cycle and allows for the subsequent colonization of new habitats. Dispersal is likely to be critical for species survival and appears to be a precisely regulated process that involves a complex network of genes and signal transduction systems. Sophisticated molecular mechanisms control the transition of sessile biofilm cells into dispersal cells and their coordinated detachment and release in the bulk liquid. Dispersal cells appear to be specialized and exhibit a unique phenotype different from biofilm or planktonic bacteria. Further, the dispersal population is characterized by a high level of heterogeneity, reminiscent of, but distinct from, that in the biofilm, which could potentially allow for improved colonization under various environmental conditions. Here we review recent advances in characterizing the molecular mechanisms that regulate biofilm dispersal events and the impact of dispersal in a broader ecological context. Several strategies that exploit the mechanisms controlling biofilm dispersal to develop as applications for biofilm control are also presented. PMID:27337281

  14. Photovoltaik Hybrid-Solarzellen mit Nanopartikeln

    Science.gov (United States)

    Leute, Angelika

    2004-09-01

    Die organische Photovoltaik auf der Basis halbleitender Polymere bietet eine kostengünstige Alternative zu Solarzellen aus Silizium. Allerdings weisen die organischen Materialien relativ schlechte Ladungstransporteigenschaften auf. Hybrid-Solarzellen, in denen Polymere mit geeigneten anorganischen Halbleitern kombiniert sind, besitzen einerseits die praktischen Vorteile der Organik und andererseits die hohe Elektronenbeweglichkeit der anorganischen Materialien. Wissenschaftler der Technischen Universität Eindhoven haben kürzlich Hybrid-Solarzellen vorgestellt, die aus einem halbleitenden Polymer mit Zinkoxid-Nanopartikeln bestehen.

  15. Transmissionselektronenmikroskopie mit elektrostatischen Zach-Phasenplatten

    OpenAIRE

    Hettler, Simon Josef

    2015-01-01

    Elektrostatische Zach-Phasenplatten (PP) erlauben die Kontrastverstärkung von transparenten Objekten in der Transmissionselektronenmikroskopie. In der vorliegenden Arbeit wurde die Herstellung von Zach-PP optimiert und deren Auswirkung auf die Bildentstehung durch Simulationen und Experimente mit verschiedenen Proben analysiert. Die Möglichkeit der Verwendung einer Zach-PP in der Hochauflösung, der Objektwellenrekonstruktion und in Verbindung mit inelastischer Streuung wird aufgezeigt.

  16. Lernen sinojapanischer Schriftzeichen mit Bildern und Animationen

    OpenAIRE

    Soemer, Alexander

    2010-01-01

    In dieser Arbeit werden zwei visuell-mnemonische Methoden für das Paarassoziationslernen sinojapanischer Schriftzeichen (Kanji) und deren Bedeutungen vorgestellt. Die erste Methode ist das Lernen mit Bildern, welche die Bedeutung eines Schriftzeichens darstellen und dessen Elemente den Strichen des Schriftzeichens ähneln. Die zweite Methode ist das Lernen mit Animationen, welche eine Formtransformation zwischen denselben Bildern und den entsprechenden Schriftzeichen darstellen. Die beiden Met...

  17. MIT research reactor. Power uprate and utilization

    International Nuclear Information System (INIS)

    The MIT Research Reactor (MITR) is a university research reactor located on MIT campus. and has a long history in supporting research and education. Recent accomplishments include a 20% power rate to 6 MW and expanding advanced materials fuel testing program. Another important ongoing initiative is the conversion to high density low enrichment uranium (LEU) monolithic U-Mo fuel, which will consist of a new fuel element design and power increase to 7 MW. (author)

  18. Hamlet er manden i mit liv

    DEFF Research Database (Denmark)

    Rösing, Lilian Munk

    2009-01-01

    Hamlet er manden i mit liv. Min elskede. Jeg har en drøm om at frelse ham. At redde ham ud af sin mors soveværelse og ind i mit. Væk fra det ødipale Helvede han befinder sig i, fastlåst mellem et svin af en faderskikkelse (Claudius) og en alt for idealiseret far (gamle Hamlet), vågende over sin m...

  19. Regionale Dentinhaftung von Kompositrestaurationen mit unterschiedlichen Polymerisationskonzepten

    OpenAIRE

    Piltz, Carmen

    2013-01-01

    1.1.1 Hintergrund und Ziele Die Polymerisationsschrumpfung Methacrylat-basierter Komposite stellt bis zum heutigen Zeitpunkt ein bisher noch ungelöstes Problem in der modernen Zahnheilkunde dar. Insuffiziente Dentinhaftwerte mit konsekutiven postoperativen Hypersensitivitäten treiben die Dentalfirmen zur Perfektionierung dieses gefragten Füllungsmaterials an. Eine neue Kunststoffklasse (Silorane) mit der Strategie ringöffnender Monomerstrukturen während des Lichthärtens propagiert eine Min...

  20. Untersuchung der auditiven Lokalisation mit einer Lichtzeigermethode

    OpenAIRE

    Seeber, Bernhard

    2007-01-01

    Die Dissertation stellt eine neue Methode zur Untersuchung der auditiven Lokalisation vor, die sich durch eine hohe Genauigkeit und geringe methodische Einflüsse auszeichnet. Dabei wird ein Lichtzeiger rechnergesteuert mit Hilfe eines Trackballs auf die wahrgenommene Schallrichtung eingestellt. Mit Hilfe dieser Methode wird ein Verfahren zur individuell-optimalen Auswahl einer Außenohrübertragungsfunktion (AOÜF) aus mehreren fremden für Anwendungen der virtuellen Akustik entwickelt. Für die H...

  1. Ätzen von Titannitrid mit Halogenverbindungen

    OpenAIRE

    Hellriegel, Ronald

    2009-01-01

    Mit zunehmender Miniaturisierung mikroelektronischer Bauelemente steigen die Anforderungen an reproduzierbare qualitätskonforme Schichten. Um die zur Herstellung notwendigen ALD/PVD/CVD-Schichtabscheideanlagen in einen zuverlässigen Zustand zu versetzen, ist eine regelmäßige Kammerreinigung notwendig. Während des Abscheideprozesses werden nicht nur das Substrat, sondern auch die umliegenden Kammerteile beschichtet. Diese Schichten wachsen mit jedem Beschichtungszyklus weiter an. Der Stres...

  2. Hydraulic resistance of biofilms

    KAUST Repository

    Dreszer, C.

    2013-02-01

    Biofilms may interfere with membrane performance in at least three ways: (i) increase of the transmembrane pressure drop, (ii) increase of feed channel (feed-concentrate) pressure drop, and (iii) increase of transmembrane passage. Given the relevance of biofouling, it is surprising how few data exist about the hydraulic resistance of biofilms that may affect the transmembrane pressure drop and membrane passage. In this study, biofilms were generated in a lab scale cross flow microfiltration system at two fluxes (20 and 100Lm-2h-1) and constant cross flow (0.1ms-1). As a nutrient source, acetate was added (1.0mgL-1 acetate C) besides a control without nutrient supply. A microfiltration (MF) membrane was chosen because the MF membrane resistance is very low compared to the expected biofilm resistance and, thus, biofilm resistance can be determined accurately. Transmembrane pressure drop was monitored. As biofilm parameters, thickness, total cell number, TOC, and extracellular polymeric substances (EPS) were determined, it was demonstrated that no internal membrane fouling occurred and that the fouling layer actually consisted of a grown biofilm and was not a filter cake of accumulated bacterial cells. At 20Lm-2h-1 flux with a nutrient dosage of 1mgL-1 acetate C, the resistance after 4 days reached a value of 6×1012m-1. At 100Lm-2h-1 flux under the same conditions, the resistance was 5×1013m-1. No correlation of biofilm resistance to biofilm thickness was found; Biofilms with similar thickness could have different resistance depending on the applied flux. The cell number in biofilms was between 4×107 and 5×108 cellscm-2. At this number, bacterial cells make up less than a half percent of the overall biofilm volume and therefore did not hamper the water flow through the biofilm significantly. A flux of 100Lm-2h-1 with nutrient supply caused higher cell numbers, more biomass, and higher biofilm resistance than a flux of 20Lm-2h-1. However, the biofilm thickness

  3. Meningococcal biofilm formation

    DEFF Research Database (Denmark)

    Lappann, M.; Haagensen, Janus Anders Juul; Claus, H.;

    2006-01-01

    We show that in a standardized in vitro flow system unencapsulated variants of genetically diverse lineages of Neisseria meningitidis formed biofilms, that could be maintained for more than 96 h. Biofilm cells were resistant to penicillin, but not to rifampin or ciprofloxacin. For some strains......, microcolony formation within biofilms was observed. Microcolony formation in strain MC58 depended on a functional copy of the pilE gene encoding the pilus subunit pilin, and was associated with twitching of cells. Nevertheless, unpiliated pilE mutants formed biofilms showing that attachment and accumulation......X alleles was identified among genetically diverse meningococcal strains. PilX alleles differed in their propensity to support autoaggregation of cells in suspension, but not in their ability to support microcolony formation within biofilms in the continuous flow system....

  4. Biofilms in wounds

    DEFF Research Database (Denmark)

    Cooper, R A; Bjarnsholt, Thomas; Alhede, M

    2014-01-01

    Following confirmation of the presence of biofilms in chronic wounds, the term biofilm became a buzzword within the wound healing community. For more than a century pathogens have been successfully isolated and identified from wound specimens using techniques that were devised in the nineteenth...... extracellular polymeric substances (EPS). Cells within such aggregations (or biofilms) display varying physiological and metabolic properties that are distinct from those of planktonic cells, and which contribute to their persistence. There are many factors that influence healing in wounds and the discovery...... of biofilms in chronic wounds has provided new insight into the reasons why. Increased tolerance of biofilms to antimicrobial agents explains the limited efficacy of antimicrobial agents in chronic wounds and illustrates the need to develop new management strategies. This review aims to explain the nature...

  5. Biofilm Cohesive Strength as a Basis for Biofilm Recalcitrance: Are Bacterial Biofilms Overdesigned?

    Science.gov (United States)

    Aggarwal, Srijan; Stewart, Philip S; Hozalski, Raymond M

    2015-01-01

    Bacterial biofilms are highly resistant to common antibacterial treatments, and several physiological explanations have been offered to explain the recalcitrant nature of bacterial biofilms. Herein, a biophysical aspect of biofilm recalcitrance is being reported on. While engineering structures are often overdesigned with a factor of safety (FOS) usually under 10, experimental measurements of biofilm cohesive strength suggest that the FOS is on the order of thousands. In other words, bacterial biofilms appear to be designed to withstand extreme forces rather than typical or average loads. In scenarios requiring the removal or control of unwanted biofilms, this emphasizes the importance of considering strategies for structurally weakening the biofilms in conjunction with bacterial inactivation.

  6. MIT 12 Tesla Coil test results

    International Nuclear Information System (INIS)

    Test results from the MIT 12 Tesla Coil experiment are presented. The coil was tested in the High Field Test Facility (HFTF) of the Lawrence Livermore National Laboratory in October 1984 and January 1985. The experiment measured the performance of an Internally Cooled, Cabled Superconductor (ICCS) of practical size, intended for use in magnetic fusion experiments. The MIT coil carried 15 kA at 11 T for 5 min with no sign of instability. A half turn length in a 10 T field was able to absorb a heat load in 4 msec of more than 200 mJ/cm3 of cable volume while carrying a current of 12 kA. The MIT coil successfully met the performance requirements of the Department of Energy's 12 Tesla Coil Program

  7. Enantioselektive Transferhydrierung mit Ruthenium(II)-Komplexen

    OpenAIRE

    Henning, Frauke

    2003-01-01

    Eine Vielzahl chiraler Liganden und Komplexe wurden als Katalysatoren in der enantioselektiven Transferhydrierung von Acetophenon mit den Wasserstoffdonoren 2-Propanol und Ameisensäure getestet. Vier dreizähnige axial chirale Binaphthyle erzielen in situ mit Tris-(triphenylphosphanyl)ruthenium(II)-chlorid hohe Enantiomerenüberschüsse von bis zu 98% und Ausbeuten über 90% unter optimierten Reaktionsbedingungen. Es wird ein deutlicher OH-Effekt beobachtet, während ein NH-Effekt nicht bestätigt ...

  8. Entwicklung eines Ultraschallkatheters mit integriertem Mikroantrieb

    OpenAIRE

    Ledworuski, Ralf

    2006-01-01

    In der medizinischen Diagnostik werden Ultraschallkatheter häufig eingesetzt, um Gefäße wie z. B. Arterien oder den Gallengang auf Ablagerungen und krankhafte Veränderungen zu untersuchen und diese in einem sehr frühen Stadium zu erkennen. Voraussetzung dafür ist eine kontrastreiche Gefäßdarstellung mit guter Auflösung. Kathetersysteme aus dem Bereich des intravaskulären Ultraschalls (IVUS) und Minisonden des endoskopischen Ultraschalls (EUS) erzeugen zirkuläre Ultraschallbilder mit dem Ultra...

  9. Herstellung von Metallkomplexen mit schwefelreichen Liganden

    OpenAIRE

    Chrzanowski, Lars Stefan von

    2005-01-01

    Die vorliegende Arbeit beschäftigt sich mit der Synthese und Charakterisierung von neuen Übergangsmetallkomplexen der ersten und zweiten Nebengruppe mit schwefelreichen Liganden. Die neuen Thiokronenetherkomplexe (1,4,7,10-Tetrathiacyclododecan)silber(I)trifluoromethansulfonat 5, Di(3,6,9,14-Tetrathiabicyclo-[9.2.1]tetradeca-11,13-dien)silber(I)trifluoromethansulfonat 6, (1,4,7,10,13,16-Hexathiacyclooctadecan)silber(I)trifluoromethansulfonat 7 und Diiodo(1,4,7,10,13,16-Hexathiacyclooctadecan)...

  10. 3. Zusammenarbeit mit Osteuropa und der GUS

    OpenAIRE

    Guggenbühl, Tanja; Tschumi Canosa, Xavier

    2009-01-01

    Die neue Rechtsgrundlage für die Zusammenarbeit mit den Staaten Osteuropas und der Gemeinschaft Unabhängiger Staaten (GUS) trat am 1. Juni 2007 in Kraft. Sie ist sowohl für den Beitrag der Schweiz zur Erweiterung der Europäischen Union (EU) als auch für die Zusammenarbeit mit den Oststaaten massgebend. Während der Bundesrat eine Kürzung der Mittel für die Ostzusammenarbeit vorgesehen hatte, um dadurch einen Teil der Finanzierung der Kohäsionsmilliarde zu kompensieren, konnte der Rahmenkredit ...

  11. Studying bacterial multispecies biofilms

    DEFF Research Database (Denmark)

    Røder, Henriette Lyng; Sørensen, Søren Johannes; Burmølle, Mette

    2016-01-01

    The high prevalence and significance of multispecies biofilms have now been demonstrated in various bacterial habitats with medical, industrial, and ecological relevance. It is highly evident that several species of bacteria coexist and interact in biofilms, which highlights the need for evaluating...... the approaches used to study these complex communities. This review focuses on the establishment of multispecies biofilms in vitro, interspecies interactions in microhabitats, and how to select communities for evaluation. Studies have used different experimental approaches; here we evaluate the benefits...... and drawbacks of varying the degree of complexity. This review aims to facilitate multispecies biofilm research in order to expand the current limited knowledge on interspecies interactions. Recent technological advances have enabled total diversity analysis of highly complex and diverse microbial communities...

  12. Biofilm in wound care.

    Science.gov (United States)

    Rajpaul, Kumal

    2015-03-01

    A biofilm can be described as a microbial colony encased in a polysaccharide matrix which can become attached to a wound surface. This can affect the healing potential of chronic wounds due to the production of destructive enzymes and toxins which can promote a chronic inflammatory state within the wound. Biofilms can be polymicrobial and can result in delayed wound healing and chronic wound infection resistant to antibiotics, leading to prolonged hospitalisation for some patients. There appears to be a correlation between biofilms and non-healing in chronic wounds. It is suggested that biofilms are a major player in the chronicity of wounds. They are a complex concept to diagnose and management needs to be multifactorial.

  13. Compaction and relaxation of biofilms

    KAUST Repository

    Valladares Linares, R.

    2015-06-18

    Operation of membrane systems for water treatment can be seriously hampered by biofouling. A better characterization of biofilms in membrane systems and their impact on membrane performance may help to develop effective biofouling control strategies. The objective of this study was to determine the occurrence, extent and timescale of biofilm compaction and relaxation (decompaction), caused by permeate flux variations. The impact of permeate flux changes on biofilm thickness, structure and stiffness was investigated in situ and non-destructively with optical coherence tomography using membrane fouling monitors operated at a constant crossflow velocity of 0.1 m s−1 with permeate production. The permeate flux was varied sequentially from 20 to 60 and back to 20 L m−2 h−1. The study showed that the average biofilm thickness on the membrane decreased after elevating the permeate flux from 20 to 60 L m−2 h−1 while the biofilm thickness increased again after restoring the original flux of 20 L m−2 h−1, indicating the occurrence of biofilm compaction and relaxation. Within a few seconds after the flux change, the biofilm thickness was changed and stabilized, biofilm compaction occurred faster than the relaxation after restoring the original permeate flux. The initial biofilm parameters were not fully reinstated: the biofilm thickness was reduced by 21%, biofilm stiffness had increased and the hydraulic biofilm resistance was elevated by 16%. Biofilm thickness was related to the hydraulic biofilm resistance. Membrane performance losses are related to the biofilm thickness, density and morphology, which are influenced by (variations in) hydraulic conditions. A (temporarily) permeate flux increase caused biofilm compaction, together with membrane performance losses. The impact of biofilms on membrane performance can be influenced (increased and reduced) by operational parameters. The article shows that a (temporary) pressure increase leads to more

  14. Interactions in multispecies biofilms

    DEFF Research Database (Denmark)

    Burmølle, Mette; Ren, Dawei; Bjarnsholt, Thomas;

    2014-01-01

    The recent focus on complex bacterial communities has led to the recognition of interactions across species boundaries. This is particularly pronounced in multispecies biofilms, where synergistic interactions impact the bacterial distribution and overall biomass produced. Importantly, in a number...... of settings, the interactions in a multispecies biofilm affect its overall function, physiology, or surroundings, by resulting in enhanced resistance, virulence, or degradation of pollutants, which is of significant importance to human health and activities. The underlying mechanisms causing these synergistic...

  15. Grosse Axiallager mit Hybridschmierung - Theoretische und experimentelle Betrachtungen

    DEFF Research Database (Denmark)

    Santos, Ilmar; Fuerst, Axel

    2003-01-01

    Der vorliegende Artikel praesentiert die Simulation eines grossen axialen Kippsegmentlagers unter Beruecksichtigung der hybriden Schmierung, d.h. gleichzeitige hydrodynamische und hydrostatische Schmierung. Ein Vergleich mit Messungen zeigt, dass fuer das betrachtete Lager mit 2,2 m Durchmesser d...

  16. Bacteriophages and Biofilms

    Directory of Open Access Journals (Sweden)

    David R. Harper

    2014-06-01

    Full Text Available Biofilms are an extremely common adaptation, allowing bacteria to colonize hostile environments. They present unique problems for antibiotics and biocides, both due to the nature of the extracellular matrix and to the presence within the biofilm of metabolically inactive persister cells. Such chemicals can be highly effective against planktonic bacterial cells, while being essentially ineffective against biofilms. By contrast, bacteriophages seem to have a greater ability to target this common form of bacterial growth. The high numbers of bacteria present within biofilms actually facilitate the action of bacteriophages by allowing rapid and efficient infection of the host and consequent amplification of the bacteriophage. Bacteriophages also have a number of properties that make biofilms susceptible to their action. They are known to produce (or to be able to induce enzymes that degrade the extracellular matrix. They are also able to infect persister cells, remaining dormant within them, but re-activating when they become metabolically active. Some cultured biofilms also seem better able to support the replication of bacteriophages than comparable planktonic systems. It is perhaps unsurprising that bacteriophages, as the natural predators of bacteria, have the ability to target this common form of bacterial life.

  17. Sexualisierte Gewalt gegen Menschen mit Behinderung in Institutionen

    OpenAIRE

    Zemp, Aiha

    2002-01-01

    Es werden zwei Studien vorgestellt: "'Weil das alles weh tut mit Gewalt' - Sexuelle Ausbeutung von Mädchen und Frauen mit Behinderung" (Zemp u. Pircher 1996) und "Sexualisierte Gewalt im behinderten Alltag - Jungen und Männer mit Behinderung als Opfer und Täter" (Zemp et al. 1997). In den vorliegenden Untersuchungen haben wir uns auf Frauen und Männer mit Behinderung konzentriert, die aufgrund ihrer körperlichen, geistigen und/oder psychischen Behinderung in einer Institution leben. S...

  18. Abbildendes Mikrowellen-Spektrometer mit Apertursynthese

    OpenAIRE

    Jirousek, Matthias

    2011-01-01

    In dieser Arbeit wird die neuartige Kombination des hochauflösenden radiometrischen Abbildungsverfahrens Apertursynthese mit einer spektralen Messung untersucht und im System ANSAS umgesetzt. Diese Verknüpfung ermöglicht z.B. in der Fernerkundung eine umfangreichere Erdbeobachtung zur genaueren Erfassung geophysikalischer Parameter. Die messtechnische Verifikation wurde anhand verschiedener Abbildungsszenarien untersucht und damit die Machbarkeit eines solchen Systemkonzepts demonstriert.

  19. MIT professor wins major international math prize

    CERN Multimedia

    Allen, S

    2004-01-01

    Mathematicians Isadore Singer of MIT and Sir Michael Francis Atiyah of the University of Edinburgh will share an $875,000 award as winners of the second Abel Prize, which some hope will come to be seen as a Nobel Prize for math.

  20. Wrestling with Pedagogical Change: The TEAL Initiative at MIT

    Science.gov (United States)

    Breslow, Lori

    2010-01-01

    In the late 1990s, the physics department at the Massachusetts Institute of Technology (MIT) had a problem. The department was responsible for teaching the two required physics courses that are part of the General Institute Requirements (GIRs), MIT's core curriculum--Physics I (mechanics, or in MIT parlance, 8.01) and Physics II (electricity and…

  1. AdMit: adaptive mixtures of student-t distributions

    NARCIS (Netherlands)

    D. David (David); L.F. Hoogerheide (Lennart); H.K. van Dijk (Herman)

    2009-01-01

    textabstractThis note presents the package AdMit (Ardia et al., 2008, 2009), an R implementation of the adaptive mixture of Student-t distributions (AdMit) procedure developed by Hoogerheide (2006); see also Hoogerheide et al. (2007); Hoogerheide and van Dijk (2008). The AdMit strategy consists of t

  2. Biofilms and the food industry

    Directory of Open Access Journals (Sweden)

    Nathanon Trachoo

    2003-11-01

    Full Text Available In the past, interest in biofilms was limited to research related to water distribution systems, waste water treatment and dental plaques. Biofilm has become a more popular research topic in many other areas in recent years including food safety. Biofilm formation can compromise the sanitation of food surfaces and environmental surfaces by spreading detached organisms to other areas of processing plants. Unfortunately, these detached organisms are not similar to normal microorganisms suspended in an aquatic environment but are more resistant to several stresses or microbial inactivation including some food preservation methods. Microstructures of biofilms as revealed by different types of microscopic techniques showed that biofilms are highly complex and consist of many symbiotic organisms, some of which are human pathogens. This article reviewed the process of biofilm formation, the significance of biofilms on food or food contact surfaces, their ability to protect foodborne pathogens from environmental stresses and recent methods for the study of biofilms on food contact surfaces.

  3. Microalgal biofilms for wastewater treatment

    OpenAIRE

    Boelee, N.C.

    2013-01-01

    The objective of this thesis was to explore the possibilities of using microalgal biofilms for the treatment of municipal wastewater, with a focus on the post-treatment of municipal wastewater effluent. The potential of microalgal biofilms for wastewater treatment was first investigated using a scenario analysis. Then biofilms were grown on wastewater treatment plant effluent in horizontal flow cells under different nutrient loads to determine the maximum uptake capacity of the biofilms for N...

  4. Biofilm Cohesive Strength as a Basis for Biofilm Recalcitrance: Are Bacterial Biofilms Overdesigned?

    OpenAIRE

    Srijan Aggarwal; Philip S. Stewart; Hozalski, Raymond M.

    2016-01-01

    Bacterial biofilms are highly resistant to common antibacterial treatments, and several physiological explanations have been offered to explain the recalcitrant nature of bacterial biofilms. Herein, a biophysical aspect of biofilm recalcitrance is being reported on. While engineering structures are often overdesigned with a factor of safety (FOS) usually under 10, experimental measurements of biofilm cohesive strength suggest that the FOS is on the order of thousands. In other words, bacteria...

  5. Flight research with the MIT Daedalus prototype

    Science.gov (United States)

    Bussolari, Steven R.; Youngren, Harold H.; Langford, John S.

    1987-01-01

    The MIT Light Eagle human-powered aircraft underwent long-duration testing over Rogers Dry Lake in California during January, 1987. Designed as a prototype for the MIT Daedalus Project, the Light Eagle's forty-eight flights provided pilot training, established new distance records for human-powered flight, and provided quantitative data through a series of instrumented flight experiments. The experiments focused on: (1) evaluating physiological loads on the pilot, (2) determining airframe power requirements, and (3) developing an electronic flight control system. This paper discusses the flight test program, its results and their implications for the follow-on Daedalus aircraft, and the potential uses of the Light Eagle as a low Reynolds number testbed.

  6. Aufgabenorientierte Kopplung von Sensoren mit unterschiedlichen Abtasteigenschaften

    OpenAIRE

    Robl, Christian

    2007-01-01

    Die Sensorkopplung auf Signal-Level für Regelungszwecke wird in drei funktionelle Blöcke - Synchronisation, Sensordatenvorverarbeitung und Sensordatenfusion - unterteilt. Es werden dafür Methoden erarbeitet und mit klassischen Verfahren verglichen. Die Sensoren werden anhand ihres Abtastverhaltens in vier Klassen unterteilt. Es werden dafür geeignete Simulationsmodelle abgeleitet. Die Erweiterung von MatLab/SimuLink ermöglicht die Verwendung des gleichen Blockschaltbilds für Software- und Har...

  7. Kurz zum Klima: Solarstromboom mit Nebenwirkungen

    OpenAIRE

    Johann Wackerbauer; Jana Lippelt

    2012-01-01

    Die deutsche Solarstrombranche befindet sich in einer Phase der Marktbereinigung. Der Sonnenstromboom geht mit Überkapazitäten bei den Herstellern von Solarzellen und Modulen und fallenden Preisen einher. Trotz einer großzügigen Förderung gerät die als Zukunftsindustrie bezeichnete deutsche Photovoltaikindustrie in eine Absatzkrise und die Förderung der Photovoltaik in Deutschland erweist sich als industriepolitisches Debakel: Während die asiatischen Produzenten gezielt ihre Marktanteile ausb...

  8. MIT App Inventor: Enabling Personal Mobile Computing

    OpenAIRE

    Pokress, Shaileen Crawford; Veiga, José Juan Dominguez

    2013-01-01

    MIT App Inventor is a drag-and-drop visual programming tool for designing and building fully functional mobile apps for Android. App Inventor promotes a new era of personal mobile computing in which people are empowered to design, create, and use personally meaningful mobile technology solutions for their daily lives, in endlessly unique situations. App Inventor's intuitive programming metaphor and incremental development capabilities allow the developer to focus on the logic for programming ...

  9. Textualizing cultures: thinking beyond the MIT controversy

    OpenAIRE

    Callahan, William A.

    2015-01-01

    This essay examines how the MIT Controversy hardened identities in terms of the timeworn template of geopolitical conflict of national stereotypes. It critically analyzes the Chinese students’ response to the “Visualizing Cultures” project by putting it in the context of the PRC’s patriotic education policy that securitizes culture by focusing on identity as difference in a zero-sum game that distinguishes civilization from barbarism, and China from the rest of the world. It cr...

  10. Pseudomonas aeruginosa Biofilms

    DEFF Research Database (Denmark)

    Alhede, Maria; Bjarnsholt, Thomas; Givskov, Michael;

    2014-01-01

    biofilms, which protect the aggregated, biopolymer-embedded bacteria from the detrimental actions of antibiotic treatments and host immunity. A key component in the protection against innate immunity is rhamnolipid, which is a quorum sensing (QS)-regulated virulence factor. QS is a cell-to-cell signaling...... mechanism used to coordinate expression of virulence and protection of aggregated biofilm cells. Rhamnolipids are known for their ability to cause hemolysis and have been shown to cause lysis of several cellular components of the human immune system, for example, macrophages and polymorphonuclear leukocytes...

  11. Manipulatiaon of Biofilm Microbial Ecology

    Energy Technology Data Exchange (ETDEWEB)

    Burkhalter, R.; Macnaughton, S.J.; Palmer, R.J.; Smith, C.A.; Whitaker, K.W.; White, D.C.; Zinn, M.; kirkegaard, R.

    1998-08-09

    The Biofilm mode of growth provides such significant advantages to the members of the consortium that most organisms in important habitats are found in biofilms. The study of factors that allow manipulation of biofilm microbes in the biofilm growth state requires that reproducible biofilms by generated. The most effective monitoring of biofilm formation, succession and desquamation is with on-line monitoring of microbial biofilms with flowcell for direct observation. The biofilm growth state incorporates a second important factor, the heterogeneity in the distribution in time and space of the component members of the biofilm consortium. This heterogeneity is reflected not only in the cellular distribution but in the metabolic activity within a population of cells. Activity and cellular distribution can be mapped in four dimensions with confocal microscopy, and function can be ascertained by genetically manipulated reporter functions for specific genes or by vital stains. The methodology for understanding the microbial ecology of biofilms is now much more readily available and the capacity to manipulate biofilms is becoming an important feature of biotechnology.

  12. Manipulation of Biofilm Microbial Ecology

    Energy Technology Data Exchange (ETDEWEB)

    White, D.C.; Palmer, R.J., Jr.; Zinn, M.; Smith, C.A.; Burkhalter, R.; Macnaughton, S.J.; Whitaker, K.W.; Kirkegaard, R.D.

    1998-08-15

    The biofilm mode of growth provides such significant advantages to the members of the consortium that most organisms in important habitats are found in biofilms. The study of factors that allow manipulation of biofilm microbes in the biofilm growth state requires that reproducible biofilms be generated. The most effective monitoring of biofilm formation, succession and desaturation is with on-line monitoring of microbial biofilms with flowcell for direct observation. The biofilm growth state incorporates a second important factor, the heterogeneity in distribution in time and space of the component members of the biofilm consortium. This heterogeneity is reflected not only in the cellular distribution but in the metabolic activity within a population of cells. Activity and cellular distribution can be mapped in four dimensions with confocal microscopy, and function can be ascertained by genetically manipulated reporter functions for specific genes or by vital stains. The methodology for understanding the microbial ecology of biofilms is now much more readily available and the capacity to manipulate biofilms is becoming an important feature of biotechnology.

  13. Biofilm formation on abiotic surfaces

    DEFF Research Database (Denmark)

    Tang, Lone

    2011-01-01

    Bacteria can attach to any surface in contact with water and proliferate into complex communities enclosed in an adhesive matrix, these communities are called biofilms. The matrix makes the biofilm difficult to remove by physical means, and bacteria in biofilm can survive treatment with many...... antibiotics, disinfectants and cleaning agents. Biofilms are therefore very difficult to eradicate, and an attractive approach to limit biofilm formation is to reduce bacterial adhesion. In this thesis it was shown that lowering the surface roughness had a greater effect on bacterial retention compared....... The ability to form biofilms, the amount of eDNA produced, and the importance of eDNA for biofilm formation or stability did not correlate and varied from strain to strain. Finally, a method was developed for immobilization of living bacteria for analysis by atomic force microscopy (AFM). AFM is used...

  14. Biofilm roughness determines Cryptosporidium parvum retention in environmental biofilms.

    Science.gov (United States)

    DiCesare, E A Wolyniak; Hargreaves, B R; Jellison, K L

    2012-06-01

    The genus Cryptosporidium is a group of waterborne protozoan parasites that have been implicated in significant outbreaks of gastrointestinal infections throughout the world. Biofilms trap these pathogens and can contaminate water supplies through subsequent release. Biofilm microbial assemblages were collected seasonally from three streams in eastern Pennsylvania and used to grow biofilms in laboratory microcosms. Daily oocyst counts in the influx and efflux flow allowed the calculation of daily oocyst retention in the biofilm. Following the removal of oocysts from the influx water, oocyst attachment to the biofilm declined to an equilibrium state within 5 days that was sustained for at least 25 days. Varying the oocyst loading rate for the system showed that biofilm retention could be saturated, suggesting that discrete binding sites determined the maximum number of oocysts retained. Oocyst retention varied seasonally but was consistent across all three sites; however, seasonal oocyst retention was not consistent across years at the same site. No correlation between oocyst attachment and any measured water quality parameter was found. However, oocyst retention was strongly correlated with biofilm surface roughness and roughness varied among seasons and across years. We hypothesize that biofilm roughness and oocyst retention are dependent on environmentally driven changes in the biofilm community rather than directly on water quality conditions. It is important to understand oocyst transport dynamics to reduce risks of human infection. Better understanding of factors controlling biofilm retention of oocysts should improve our understanding of oocyst transport at different scales.

  15. The Root Canal Biofilm

    NARCIS (Netherlands)

    Sluis, van der L.W.M.; Boutsioukis, C.; Jiang, L.M.; Macedo, R.; Verhaagen, B.; Versluis, M.; Chávez de Paz, E.; Sedgley, C.M.; Kishen, A.

    2015-01-01

    The aims of root canal irrigation are the chemical dissolution or disruption and the mechanical detachment of pulp tissue, dentin debris and smear layer (instrumentation products), microorganisms (planktonic or biofilm), and their products from the root canal wall, their removal out of the root cana

  16. Der klinische Stellenwert der Polysomnographie bei Kindern mit kraniofazialen Fehlbildungssyndromen

    OpenAIRE

    Hein, Astrid

    2008-01-01

    Schlaf- und nächtliche Atemstörungen sind ein häufiges Symptom bei Kindern mit kraniofazialen Fehlbildungen, da es durch die Mittelgesichtshypoplasie zu einer Einengung der Atemwege kommen kann. Wir haben bei 28 Kindern Polysomnographien vorgenommen, um differenziertere Aussagen über die Art der schlafbezogenen Apnoen, den Zusammenhang mit bestimmten Schlafstadien und Schlafarchitektur und Korrelationen mit der mental-kognitiven Entwicklung sowie der Lebensqualität machen zu können. Diese wur...

  17. Stahlbetonplatten verstärkt mit Textilbeton unter Brandbelastung

    OpenAIRE

    Ehlig, Daniel; Jesse, Frank; Curbach, Manfred

    2009-01-01

    Im Rahmen experimenteller Untersuchungen wurden Stahlbetonplatten hergestellt, mit verschiedenen textilen Bewehrungen verstärkt, mit 125 % Gebrauchslast vorgeschädigt und anschließend unter Gebrauchslast mit einer Brandbelastung nach der Einheitstemperaturkurve (ISO-834, Cellulosic curve) beaufschlagt. Alle Platten hielten der Brandbelastung bei gleichzeitiger Biegebeanspruchung mehr als 60 Minuten stand und zeigten weder Betonabplatzungen noch andere optische Schädigungen auf. Die für dieses...

  18. Biofilm Roughness Determines Cryptosporidium parvum Retention in Environmental Biofilms

    OpenAIRE

    Wolyniak DiCesare, E. A.; Hargreaves, B. R.; Jellison, K. L.

    2012-01-01

    The genus Cryptosporidium is a group of waterborne protozoan parasites that have been implicated in significant outbreaks of gastrointestinal infections throughout the world. Biofilms trap these pathogens and can contaminate water supplies through subsequent release. Biofilm microbial assemblages were collected seasonally from three streams in eastern Pennsylvania and used to grow biofilms in laboratory microcosms. Daily oocyst counts in the influx and efflux flow allowed the calculation of d...

  19. [Bernt Ahrenholz : Verweise mit Demonstrativa im Gesprochenen Deutsch...] / Klaus Geyer

    Index Scriptorium Estoniae

    Geyer, Klaus

    2008-01-01

    Arvustus: Ahrenholz, Bernt. Verweise mit Demonstrativa im gesprochenen Deutsch : Grammatik, Zweitspracherwerb und Deutsch als Fremdsprache. Berlin ; New York : de Gruyter, 2007. (Linguistik - Impulse & Tendenzen ; 17)

  20. Penetration of Candida Biofilms by Antifungal Agents

    OpenAIRE

    Al-Fattani, Mohammed A.; Douglas, L. Julia

    2004-01-01

    A filter disk assay was used to investigate the penetration of antifungal agents through biofilms containing single and mixed-species biofilms containing Candida. Fluconazole permeated all single-species Candida biofilms more rapidly than flucytosine. The rates of diffusion of either drug through biofilms of three strains of Candida albicans were similar. However, the rates of drug diffusion through biofilms of C. glabrata or C. krusei were faster than those through biofilms of C. parapsilosi...

  1. Silver against Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Kirketerp-Møller, K.; Kristiansen, S.;

    2007-01-01

    bacteria in both the planktonic and biofilm modes of growth. The action of silver on mature in vitro biofilms of Pseudomonas aeruginosa, a primary pathogen of chronic infected wounds, was investigated. The results show that silver is very effective against mature biofilms of P. aeruginosa......, but that the silver concentration is important. A concentration of 5-10 ig/mL silver sulfadiazine eradicated the biofilm whereas a lower concentration (1 ig/mL) had no effect. The bactericidal concentration of silver required to eradicate the bacterial biofilm was 10-100 times higher than that used to eradicate...... planktonic bacteria. These observations strongly indicate that the concentration of silver in currently available wound dressings is much too low for treatment of chronic biofilm wounds. It is suggested that clinicians and manufacturers of the said wound dressings consider whether they are treating wounds...

  2. Electrochemical biofilm control: A review

    Science.gov (United States)

    Sultana, Sujala T; Babauta, Jerome T; Beyenal, Haluk

    2015-01-01

    One of the methods of controlling biofilms that has widely been discussed in the literature is to apply a potential or electrical current to a metal surface on which the biofilm is growing. Although electrochemical biofilm control has been studied for decades, the literature is often conflicting, as is detailed in this review. The goals of this review are to (1) present the current status of knowledge regarding electrochemical biofilm control, (2) establish a basis for a fundamental definition of electrochemical biofilm control and requirements for studying it, (3) discuss current proposed mechanisms, and (4) introduce future directions in the field. It is expected that the review will provide researchers with guidelines on comparing data sets across the literature and generating comparable data sets. The authors believe that, with the correct design, electrochemical biofilm control has great potential for industrial use. PMID:26592420

  3. Biofilm susceptibility to metal toxicity.

    Science.gov (United States)

    Harrison, Joe J; Ceri, Howard; Stremick, Carol A; Turner, Raymond J

    2004-12-01

    This study compared bacterial biofilm and planktonic cell susceptibility to metal toxicity by evaluating the minimum inhibitory concentration (MIC), the planktonic minimum bactericidal concentration (MBC), and minimum biofilm eradication concentration (MBEC) using the MBEC device. In total, 17 metal cations and oxyanions, chosen to represent groups VIB to VIA of the periodic table, were each tested on biofilm and planktonic cultures of Escherichia coli JM109, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853. In contrast to control antibiotic assays, where biofilm cultures were 2 to 64 times less susceptible to killing than logarithmically growing planktonic bacteria, metal compounds killed planktonic and biofilm cultures at the same concentration in the vast majority of combinations. Our data indicate that, under the conditions reported, growth in a biofilm does not provide resistance to bacteria against killing by metal cations or oxyanions.

  4. Biofilms: a developing microscopic community

    Directory of Open Access Journals (Sweden)

    Rivera Sandra Patricia

    2004-09-01

    Full Text Available Biofilms are microbial communities composed by different microbiota embebbed in a special adaptive environment. These communities show different characteristics such as heterogeneity, diversity in microenvironments, capacity to resist antimicrobial therapy and ability to allow bacterial communication. These characteristics convert them in complex organizations that are difficult to eradicate in their own environment. In the man, biofilms are associated to a great number of slow-development infectious processes which greatly difficulties their eradication. In the industry and environment, biofilms are centered in processes known as biofouling and bioremediation. The former is the contamination of a system due to the microbial activity of a biofilm. The latter uses biofilms to improve the conditions of a contaminated system. The study of biofilms is a new and exciting field which is constantly evolving and whose implications in medicine and industry would have important repercussions for the humankind.

  5. Electrochemical biofilm control: a review.

    Science.gov (United States)

    Sultana, Sujala T; Babauta, Jerome T; Beyenal, Haluk

    2015-01-01

    One of the methods of controlling biofilms that has widely been discussed in the literature is to apply a potential or electrical current to a metal surface on which the biofilm is growing. Although electrochemical biofilm control has been studied for decades, the literature is often conflicting, as is detailed in this review. The goals of this review are: (1) to present the current status of knowledge regarding electrochemical biofilm control; (2) to establish a basis for a fundamental definition of electrochemical biofilm control and requirements for studying it; (3) to discuss current proposed mechanisms; and (4) to introduce future directions in the field. It is expected that the review will provide researchers with guidelines on comparing datasets across the literature and generating comparable datasets. The authors believe that, with the correct design, electrochemical biofilm control has great potential for industrial use.

  6. Biofilm formation and microbial corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, R.; Porcella, D.

    1992-07-01

    Biofilms-colonies of microorganisms growing on surfaces - can greatly accelerate the corrosion rates of metals and alloys in utility water systems. Fundamental EPRI research is showing how mechanisms of biofilm formation, interactions between bacterial species, and metabolic activities control such biofilm properties as corrosive potential This research is identifying methods to control biofilm development and prevent microbially influenced corrosion. The results should also apply to the control of other processes involving biological consortia, including the bioremediation of contaminated groundwater and soil and the biodesulfurization of coal.

  7. Biofilm and Dental Biomaterials

    Directory of Open Access Journals (Sweden)

    Marit Øilo

    2015-05-01

    Full Text Available All treatment involving the use of biomaterials in the body can affect the host in positive or negative ways. The microbiological environment in the oral cavity is affected by the composition and shape of the biomaterials used for oral restorations. This may impair the patients’ oral health and sometimes their general health as well. Many factors determine the composition of the microbiota and the formation of biofilm in relation to biomaterials such as, surface roughness, surface energy and chemical composition, This paper aims to give an overview of the scientific literature regarding the association between the chemical, mechanical and physical properties of dental biomaterials and oral biofilm formation, with emphasis on current research and future perspectives.

  8. Tissue Velocity, Strain und Strain Rate bei Hunden mit Mitralklappenendokardiose

    OpenAIRE

    Javornik, Ana

    2007-01-01

    In der vorliegenden Arbeit „Tissue Velocity, Strain und Strain Rate bei Hunden mit Mitralklappenendokardiose“ wurden erstmals die Geschwindigkeits- und Verformungsparameter zur Evaluierung von Hunden mit Mitralklappenendokardiose angewendet. Diese erweisen sich als neue und viel versprechende Möglichkeiten zur Quantifizierung der regionalen Myokardfunktion. Die myokardialen Funktionsparameter finden in der Humanmedizin weit verbreitete Anwendung und auch in der Tiermedizin erlangen sie zunehm...

  9. Staphylococcus aureus biofilms: recent developments in biofilm dispersal.

    Science.gov (United States)

    Lister, Jessica L; Horswill, Alexander R

    2014-01-01

    Staphylococcus aureus is a major cause of nosocomial and community-acquired infections and represents a significant burden on the healthcare system. S. aureus attachment to medical implants and host tissue, and the establishment of a mature biofilm, play an important role in the persistence of chronic infections. The formation of a biofilm, and encasement of cells in a polymer-based matrix, decreases the susceptibility to antimicrobials and immune defenses, making these infections difficult to eradicate. During infection, dispersal of cells from the biofilm can result in spread to secondary sites and worsening of the infection. In this review, we discuss the current understanding of the pathways behind biofilm dispersal in S. aureus, with a focus on enzymatic and newly described broad-spectrum dispersal mechanisms. Additionally, we explore potential applications of dispersal in the treatment of biofilm-mediated infections.

  10. Microalgal biofilms for wastewater treatment

    NARCIS (Netherlands)

    Boelee, N.C.

    2013-01-01

    The objective of this thesis was to explore the possibilities of using microalgal biofilms for the treatment of municipal wastewater, with a focus on the post-treatment of municipal wastewater effluent. The potential of microalgal biofilms for wastewater treatment was first investigated using a scen

  11. Microbial ecology of phototrophic biofilms

    NARCIS (Netherlands)

    Roeselers, G.

    2007-01-01

    Biofilms are layered structures of microbial cells and an extracellular matrix of polymeric substances, associated with surfaces and interfaces. Biofilms trap nutrients for growth of the enclosed microbial community and help prevent detachment of cells from surfaces in flowing systems. Phototrophic

  12. Experimental evolution in biofilm populations.

    Science.gov (United States)

    Steenackers, Hans P; Parijs, Ilse; Foster, Kevin R; Vanderleyden, Jozef

    2016-05-01

    Biofilms are a major form of microbial life in which cells form dense surface associated communities that can persist for many generations. The long-life of biofilm communities means that they can be strongly shaped by evolutionary processes. Here, we review the experimental study of evolution in biofilm communities. We first provide an overview of the different experimental models used to study biofilm evolution and their associated advantages and disadvantages. We then illustrate the vast amount of diversification observed during biofilm evolution, and we discuss (i) potential ecological and evolutionary processes behind the observed diversification, (ii) recent insights into the genetics of adaptive diversification, (iii) the striking degree of parallelism between evolution experiments and real-life biofilms and (iv) potential consequences of diversification. In the second part, we discuss the insights provided by evolution experiments in how biofilm growth and structure can promote cooperative phenotypes. Overall, our analysis points to an important role of biofilm diversification and cooperation in bacterial survival and productivity. Deeper understanding of both processes is of key importance to design improved antimicrobial strategies and diagnostic techniques.

  13. Experimental evolution in biofilm populations

    Science.gov (United States)

    Steenackers, Hans P.; Parijs, Ilse; Foster, Kevin R.; Vanderleyden, Jozef

    2016-01-01

    Biofilms are a major form of microbial life in which cells form dense surface associated communities that can persist for many generations. The long-life of biofilm communities means that they can be strongly shaped by evolutionary processes. Here, we review the experimental study of evolution in biofilm communities. We first provide an overview of the different experimental models used to study biofilm evolution and their associated advantages and disadvantages. We then illustrate the vast amount of diversification observed during biofilm evolution, and we discuss (i) potential ecological and evolutionary processes behind the observed diversification, (ii) recent insights into the genetics of adaptive diversification, (iii) the striking degree of parallelism between evolution experiments and real-life biofilms and (iv) potential consequences of diversification. In the second part, we discuss the insights provided by evolution experiments in how biofilm growth and structure can promote cooperative phenotypes. Overall, our analysis points to an important role of biofilm diversification and cooperation in bacterial survival and productivity. Deeper understanding of both processes is of key importance to design improved antimicrobial strategies and diagnostic techniques. PMID:26895713

  14. Antibiotic resistance of bacterial biofilms

    DEFF Research Database (Denmark)

    Hoiby, N.; Bjarnsholt, T.; Givskov, M.;

    2010-01-01

    A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and DNA. Bacterial biofilms cause chronic infections because they show increased tolerance to antibiotics and disinfectant chemicals as well as resisting phagocytosis...... and other components of the body's defence system. The persistence of, for example, staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infection in cystic fibrosis patients is caused by biofilm-growing mucoid strains....... Characteristically, gradients of nutrients and oxygen exist from the top to the bottom of biofilms and these gradients are associated with decreased bacterial metabolic activity and increased doubling times of the bacterial cells; it is these more or less dormant cells that are responsible for some of the tolerance...

  15. Antibiotic tolerance and microbial biofilms

    DEFF Research Database (Denmark)

    Folkesson, Anders

    Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We study the dynamics of antibiotic action within hydrodynamic flow chamber biofilms of Escherichia coli and Pseudomonas aeruginosa using isogenic mutants and fluorescent gene...... expression reporters and we address the question of how biofilm organization affects antibiotic susceptibility. The dynamics of microbial killing is monitored by viable count determination, and confocal laser microscopy. Our work shows that the apparent increased antibiotic tolerance is due to the formation...... of antibiotic tolerant subpopulations within the biofilm. The formation of these subpopulations is highly variable and dependent on the antibiotic used, the biofilm structural organization and the induction of specific tolerance mechanisms....

  16. MIT 12 TESLA coil experimental results

    International Nuclear Information System (INIS)

    The MIT 12 tesla coil was fabricated using a 486-strand bronze-matrix Nb3Sn, JBK-75 superalloy sheathed Internally Cooled Cabled Superconductor (ICCS). The rectangularly shaped ICCS conductor was wound into three double pancakes prior to a six-day reaction (4 days at 7000C followed by 2 days at 7300C). Prior to installation in the High Field Test Facility (HFTF) at LLNL the three subcoils were insulated and epoxy potted. With the HFTF providing a 9 T background field, the test coil was used to raise the central field up to 12 T. Measurements of critical current are reported for fields in the 11 to 12 T range for temperatures of 4.2, 5.2 and 7.5 K with supercritical as well as 1 atm, two-phase internal helium. Steady-state, inductively heated as well as quench induced operations are described

  17. Oral Biofilm Architecture on Natural Teeth

    NARCIS (Netherlands)

    Zijnge, Vincent; van Leeuwen, M. Barbara M.; Degener, John E.; Abbas, Frank; Thurnheer, Thomas; Gmuer, Rudolf; Harmsen, Hermie J. M.

    2010-01-01

    Periodontitis and caries are infectious diseases of the oral cavity in which oral biofilms play a causative role. Moreover, oral biofilms are widely studied as model systems for bacterial adhesion, biofilm development, and biofilm resistance to antibiotics, due to their widespread presence and acces

  18. Impact of Hydrodynamics on Oral Biofilm Strength

    NARCIS (Netherlands)

    Paramonova, E.; Kalmykowa, O. J.; van der Mei, H. C.; Busscher, H. J.; Sharma, P. K.

    2009-01-01

    Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of S

  19. Oral biofilm models for mechanical plaque removal

    NARCIS (Netherlands)

    Verkaik, Martinus J.; Busscher, Henk J.; Rustema-Abbing, Minie; Slomp, Anje M.; Abbas, Frank; van der Mei, Henny C.

    2010-01-01

    In vitro plaque removal studies require biofilm models that resemble in vivo dental plaque. Here, we compare contact and non-contact removal of single and dual-species biofilms as well as of biofilms grown from human whole saliva in vitro using different biofilm models. Bacteria were adhered to a sa

  20. Bacterial biofilms: prokaryotic adventures in multicellularity

    DEFF Research Database (Denmark)

    Webb, J.S.; Givskov, Michael Christian; Kjelleberg, S.

    2003-01-01

    The development of bacterial biofilms includes both the initial social behavior of undifferentiated cells, as well as cell death and differentiation in the mature biofilm, and displays several striking similarities with higher organisms. Recent advances in the field provide new insight...... into differentiation and cell death events in bacterial biofilm development and propose that biofilms have an unexpected level of multicellularity....

  1. Multiple Mittelwertvergleiche - parametrisch und nichtparametrisch - sowie α-Adjustierungen mit praktischen Anwendungen mit R und SPSS

    OpenAIRE

    Lüpsen, Haiko

    2014-01-01

    Die etwa 20 bekanntesten parametrischen und ca. 10 nichtparametrischen Verfahren für multiple Mittelwertvergleiche sowie ca. 20 Methoden für alpha-Korrekturen bei Paarvergleichen werden vorgestellt. Dabei stehen solche im Vordergrund, die in R und/oder in SPSS ohne großen Aufwand anwendbar sind. Es werden die Voraussetzungen der Verfahren besprochen sowie Lösungen mit R und SPSS ausführlich gezeigt.

  2. Teaching ``The Physics of Energy'' at MIT

    Science.gov (United States)

    Jaffe, Robert

    2009-05-01

    New physics courses on energy are popping up at colleges and universities across the country. Many require little or no previous physics background, aiming to introduce a broad audience to this complex and critical problem, often augmenting the scientific message with economic and policy discussions. Others are advanced courses, focussing on highly specialized subjects like solar voltaics, nuclear physics, or thermal fluids, for example. About two years ago Washington Taylor and I undertook to develop a course on the ``Physics of Energy'' open to all MIT students who had taken MIT's common core of university level calculus, physics, and chemistry. By avoiding higher level prerequisites, we aimed to attract and make the subject relevant to students in the life sciences, economics, etc. --- as well as physical scientists and engineers --- who want to approach energy issues in a sophisticated and analytical fashion, exploiting their background in calculus, mechanics, and E & M, but without having to take advanced courses in thermodynamics, quantum mechanics, or nuclear physics beforehand. Our object was to interweave teaching the fundamental physics principles at the foundations of energy science with the applications of those principles to energy systems. We envisioned a course that would present the basics of statistical, quantum, and fluid mechanics at a fairly sophisticated level and apply those concepts to the study of energy sources, conversion, transport, losses, storage, conservation, and end use. In the end we developed almost all of the material for the course from scratch. The course debuted this past fall. I will describe what we learned and what general lessons our experience might have for others who contemplate teaching energy physics broadly to a technically sophisticated audience.

  3. Growing and analyzing biofilms in flow chambers

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim; Sternberg, Claus

    2011-01-01

    This unit describes the setup of flow chamber systems for the study of microbial biofilms, and methods for the analysis of structural biofilm formation. Use of flow chambers allows direct microscopic investigation of biofilm formation. The biofilms in flow chambers develop under hydrodynamic......, and disassembly and cleaning of the system. In addition, embedding and fluorescent in situ hybridization of flow chamber-grown biofilms are addressed....

  4. Significance of biofilms in dentistry.

    Science.gov (United States)

    Wróblewska, Marta; Strużycka, Izabela; Mierzwińska-Nastalska, Elżbieta

    2015-01-01

    In the past decades significant scientific progress has taken place in the knowledge about biofilms. They constitute multilayer conglomerates of bacteria and fungi, surrounded by carbohydrates which they produce, as well as substances derived from saliva and gingival fluid. Modern techniques showed significant diversity of the biofilm environment and a system of microbial communication (quorum sensing), enhancing their survival. At present it is believed that the majority of infections, particularly chronic with exacerbations, are a result of biofilm formation, particularly in the presence of biomaterials. It should be emphasised that penetration of antibiotics and other antimicrobial agents into deeper layers of a biofilm is poor, causing therapeutic problems and necessitating sometimes removal of the implant or prosthesis. Biofilms play an increasing role in dentistry as a result of more and more broad use in dental practice of plastic and implantable materials. Biofilms are produced on the surfaces of teeth as dental plaque, in the para-nasal sinuses, on prostheses, dental implants, as well as in waterlines of a dental unit, constituting a particular risk for severely immunocompromised patients. New methods of therapy and prevention of infections linked to biofilms are under development.

  5. Biofilm models for the practitioner

    DEFF Research Database (Denmark)

    Morgenroth, Eberhard Friedrich; van Loosdrecht, M. C. M.; Wanner, O.

    2000-01-01

    Even though mathematical biofilm models are extensively used in biofilm research, there has been very little application of these models in the engineering practice so far. However, practitioners would be interested in models that can be used as tools to control plant operation under dynamic...... conditions or to help them handle complex interactions between particle removal, carbon oxidation, nitrification, denitrification and biological phosphorus removal. But even though there is a whole range of biofilm models available, it is difficult for the practitioner to select the appropriate modeling...

  6. Effect of calcium on moving-bed biofilm reactor biofilms.

    Science.gov (United States)

    Goode, C; Allen, D G

    2011-03-01

    The effect of calcium concentration on the biofilm structure, microbiology, and treatment performance was evaluated in a moving-bed biofilm reactor. Three experiments were conducted in replicate laboratory-scale reactors to determine if wastewater calcium is an important variable for the design and optimization of these reactors. Biofilm structural properties, such as thickness, oxygen microprofiles, and the composition of extracellular polymeric substances (EPS) were affected by increasing calcium concentrations. Above a threshold concentration of calcium between 1 and 50 mg/L, biofilms became thicker and denser, with a shift toward increasingly proteinaceous EPS at higher calcium concentrations up to 200 mgCa2+/L. At 300 mgCa2+/L, biofilms were found to become primarily composed of inorganic calcium precipitates. Microbiology was assessed through microscopy, denaturing grade gel electrophoresis, and enumeration of higher organisms. Higher calcium concentrations were found to change the bacterial community and promote the abundant growth of filamentous organisms and various protazoa and metazoan populations. The chemical oxygen demand removal efficiency was improved for reactors at calcium concentrations of 50 mg/L and above. Reactor effluents for the lowest calcium concentration (1 mgCa2+/L) were found to be turbid (>50 NTU), as a result of the detachment of small and poorly settling planktonic biomass, whereas higher concentrations promoted settling of the suspended phase. In general, calcium was found to be an important variable causing significant changes in biofilm structure and reactor function.

  7. Stratified growth in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Werner, E.; Roe, F.; Bugnicourt, A.;

    2004-01-01

    In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct...... synthesis was restricted to a narrow band in the part of the biofilm adjacent to the source of oxygen. The zone of active GFP expression was approximately 60 Am wide in colony biofilms and 30 Am wide in flow cell biofilms. The region of the biofilm in which cells were capable of elongation was mapped...... by treating colony biofilms with carbenicillin, which blocks cell division, and then measuring individual cell lengths by transmission electron microscopy. Cell elongation was localized at the air interface of the biofilm. The heterogeneous anabolic patterns measured inside these biofilms were likely a result...

  8. Metabolism links bacterial biofilms and colon carcinogenesis.

    Science.gov (United States)

    Johnson, Caroline H; Dejea, Christine M; Edler, David; Hoang, Linh T; Santidrian, Antonio F; Felding, Brunhilde H; Ivanisevic, Julijana; Cho, Kevin; Wick, Elizabeth C; Hechenbleikner, Elizabeth M; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A; Pardoll, Drew M; White, James R; Patti, Gary J; Sears, Cynthia L; Siuzdak, Gary

    2015-06-01

    Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N(1), N(12)-diacetylspermine in both biofilm-positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N(1), N(12)-diacetylspermine levels to those seen in biofilm-negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression.

  9. Impact of hydrodynamics on oral biofilm strength.

    Science.gov (United States)

    Paramonova, E; Kalmykowa, O J; van der Mei, H C; Busscher, H J; Sharma, P K

    2009-10-01

    Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of Streptococcus oralis J22, Actinomyces naeslundii TV14-J1, and full dental plaque at shear rates ranging from 0.1 to 50 1/sec and measured their compressive strength. Subsequently, biofilm architecture was evaluated by confocal laser scanning microscopy. Multi-species biofilms were stronger than single-species biofilms, with strength values ranging from 6 to 51 Pa and from 5 to 17 Pa, respectively. In response to increased hydrodynamic shear, biofilm strength decreased, and architecture changed from uniform carpet-like to more "fluffy" with higher thickness. S. oralis biofilms grown under variable shear of 7 and 50 1/sec possessed properties intermediate of those measured at the respective single shears. PMID:19783800

  10. MIT gets good marks for fighting gender discrimination

    Science.gov (United States)

    Gwynne, Peter

    2011-05-01

    The Massachusetts Institute of Technology (MIT) has made "significant progress" in increasing the number of female faculty members, with their numbers in science and engineering almost doubling over the last decade.

  11. Nichterkennen von Vorhofflimmern bei Patienten mit kardialer Resynchronisationstherapie

    Directory of Open Access Journals (Sweden)

    Strohmer B

    2005-01-01

    Full Text Available Obwohl eine Intoleranz der kardialen Resynchronisationstherapie (CRT unüblich ist, sollten entsprechende Symptome auf ihre Ursache hin genau abgeklärt werden. Atriale Tachyarrhythmien (AT werden bei Patienten mit chronischer Herzinsuffizienz relativ häufig beobachtet. Dieser Bericht beschreibt ein rhythmologisches Problem, welches oft unerkannt bleibt und in unserem CRTKollektiv bei knapp 8 % der Patienten aufgetreten ist. Paroxysmales Vorhofflattern wurde durch den CRT-Schrittmacher nicht erkannt, da jede zweite Flatterwelle exakt mit der atrialen Ausblendzeit (PVAB = postventrikuläres atriales Blanking zusammenfiel. Dies führte zu einem Versagen der Mode-Switch-Funktion durch Nichterkennung von stabilem Vorhofflattern, welches mit sehr stabiler Zykluslänge auftrat. Dieses sog. "2:1-lock-in"-Phänomen resultierte in rascher und anhaltender biventrikulärer Stimulation, welche sich bei den betroffenen Patienten klinisch als unangenehmes Herzklopfen mit zunehmender Atemnot bemerkbar machte.

  12. Behandlung des chronischen Tinnitus mit repetitiver transkranieller Magnetstimulation

    OpenAIRE

    Kleinjung, T

    2012-01-01

    Tinnitus ist eine Funktionsstörung des Hörsystems, die von verschiedenen Strukturen und Ebenen ausgehen kann. Tinnitus geht mit neuroplastischen Veränderungen im zentralen auditorischen System einher. Existenz eines „Tinnitus-Netzwerkes“.

  13. Lung Clearance Index bei erwachsenen Patienten mit Mukoviszidose

    OpenAIRE

    Rückel, Helena Sophie

    2011-01-01

    Die Spirometrie mit Bestimmung des forcierten exspiratorischen Volumens in einer Sekunde gilt derzeit als Gold-Standard bei der Beurteilung der Lungenfunktion von Patienten mit Cystischer Fibrose. Da die spirometrische Untersuchung eine aktive Mitarbeit des Patienten erfordert, kann sie jedoch erst etwa ab dem fünften Lebensjahr durchgeführt werden. Im Gegensatz dazu kann der Lung Clearance Index (LCI), der aus Gasdilutionsuntersuchungen abgeleitet wird, in jedem Alter, d.h. auch im Säugl...

  14. Optische Detektion der magnetischen Resonanz mit modengekoppelten Femtosekunden-Pulsen

    OpenAIRE

    Schmidt, Volker

    2000-01-01

    Die vorliegende Arbeit beschäftigt sich mit dem Aufbau eines neuartigen Spektrometers zur Elektronen-Paramagnetischen Resonanz. Die konventionelle magnetische Resonanz wurde hierbei um eine optisch gepulste Detektion, mittels Titan-Saphir-Femtosekunden-Pulslaser erweitert. Als Proben wurden mit diesem neuen Spektrometer Rubin (gepulste ODEPR in Transmission), bzw. ein Fe/V-Multilayer (gepulste ODFMR in Reflektion) untersucht. Die Wechselwirkung zwischen optischer Welle und Magnetisierung...

  15. Biotransformation von 11-Desoxycortisol mit Schizosaccharomyces pombe und Aspergillus nidulans

    OpenAIRE

    Appel, Daniel

    2005-01-01

    In diesem Projekt, welches in Kooperation mit dem Institut für Biochemie der Universität des Saarlandes und der Schering AG Bergkamen durchgeführt wurde, sollte mit Hilfe von rekombinanten Spalthefestämmen, welche die humane Monooxygenase P450 CYP11B1 exprimieren, eine nachhaltigere Bio-Produktion von Hydrocortison entwickelt werden, um das bestehende Verfahren der Hydrocortisonherstellung, mittels des filamentösen Pilz Curvularia lunata zu ersetzen. Um die Optimierung der Hydrocortisonpro...

  16. Makrocyclische Malonatsysteme und deren Reaktionen mit [60]Fulleren

    OpenAIRE

    Brandmüller, Torsten

    2005-01-01

    Im Rahmen dieser Arbeit wurden verschiedenartige makrocyclische Malonate hergestellt und deren Additionsverhalten an [60]Fulleren untersucht. Zunächst wurden sieben verschiedene Makrocyclen mit identischen Alkylketten synthetisiert und charakterisiert, Anschließend wurde die Synthese auf cyclische Malonate mit unterschiedlichen Alkylketten ausgedehnt. Die so erhaltenen makrocyclischen Malonate wurden im Folgenden der Addition an C60 nach BINGEL unterworfen. Hier bilden die symmetrischen Makro...

  17. Clusteranalyse mit gemischtskalierten Merkmalen: SPSS-Makropaket Paare

    OpenAIRE

    Fickel, Norman

    1995-01-01

    Die Statistiksoftware SPSS unterstützt auch in der Version 6 nur Clusteranalysen, wenn alle Merkmale dasselbe Skalenniveau besitzen. Mit dem hier vorgestellten Makropaket Paare kann SPSS auch gemischtskalierte Daten verarbeiten. Der zugrundeliegende Algorithmus abstrahiert dazu durch Abstandsmaße von den unterschiedlichen Skalenniveaus der gegebenen Merkmale. Die Güte der gefundenen Klassifikation läßt sich mit einer Streuungszerlegung sowohl insgesamt als auch merkmalsspezifisch beurteilen

  18. Differential growth of wrinkled biofilms

    CERN Document Server

    Espeso, D R; Einarsson, B

    2015-01-01

    Biofilms are antibiotic-resistant bacterial aggregates that grow on moist surfaces and can trigger hospital-acquired infections. They provide a classical example in biology where the dynamics of cellular communities may be observed and studied. Gene expression regulates cell division and differentiation, which affect the biofilm architecture. Mechanical and chemical processes shape the resulting structure. We gain insight into the interplay between cellular and mechanical processes during biofilm development on air-agar interfaces by means of a hybrid model. Cellular behavior is governed by stochastic rules informed by a cascade of concentration fields for nutrients, waste and autoinducers. Cellular differentiation and death alter the structure and the mechanical properties of the biofilm, which is deformed according to Foppl-Von Karman equations informed by cellular processes and the interaction with the substratum. Stiffness gradients due to growth and swelling produce wrinkle branching. We are able to repr...

  19. Nanotechnology: Role in dental biofilms

    Directory of Open Access Journals (Sweden)

    Bhardwaj Sonia

    2009-01-01

    Full Text Available Biofilms are surface- adherent populations of microorganisms consisting of cells, water and extracellular matrix material Nanotechnology is promising field of science which can guide our understanding of the role of interspecies interaction in the development of biofilm. Streptococcus mutans with other species of bacteria has been known to form dental biofilm. The correlation between genetically modified bacteria Streptococcus mutans and nanoscale morphology has been assessed using AFMi.e atomic force microscopy. Nanotechnology application includes 16 O/ 18 O reverse proteolytic labeling,use of quantum dots for labeling of bacterial cells, selective removal of cariogenic bacteria while preserving the normal oral flora and silver antimicrobial nanotechnology against pathogens associated with biofilms. The future comprises a mouthwash full of smart nanomachines which can allow the harmless flora of mouth to flourish in a healthy ecosystem

  20. Hydrodynamics of catheter biofilm formation

    CERN Document Server

    Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

    2009-01-01

    A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

  1. DFB-Laser mit integriert optischer Rückkopplung für die optische Signalverarbeitung

    OpenAIRE

    Brox, Olaf

    2005-01-01

    Im Mittelpunkt dieser Arbeit stehen DFB-Laser mit integriert optischer Rückkopplung und Anwendungen dieser Komponente für die optische Signalverarbeitung. DFB-Laser mit integrierten Rückkoppelsektionen werden hergestellt und experimentell untersucht. Erstmalig erfolgen Untersuchungen an DFB-Lasern mit passiver Rückkopplung (PFL) und DFB-Lasern mit aktiver Rückkopplung (AFL), wobei das Hauptaugenmerk auf der zuverlässigen Erzeugung von Selbstpulsationen mit einer Frequenz von 40 GHz liegt. Sta...

  2. Der Lebenslauf von Menschen mit Asperger Syndrom / High-Functioning Autismus : eine Interviewstudie mit Schwerpunkt auf dem Erwachsenenalter

    OpenAIRE

    Gomolla, Annette

    2002-01-01

    Über den Lebensverlauf und insbesondere das Erwachsenenalter von Menschen mit Asperger Syndrom (AS) / High-Functioning Autismus (HFA) ist bisher wenig bekannt, insbesondere gibt es keine Studien, die die Erfahrungen und Bewertungen der Personen selbst in den Mittelpunkt stellen. Die vorliegende Studie hat sich bemüht, bestehende Informationen und Einschätzungen Dritter über Kindheit, Jugendzeit und Erwachsenenalter mit den subjektiven Sichtweisen dieser Personengruppe zu vergleichen und spezi...

  3. Strategies for combating bacterial biofilm infections

    Institute of Scientific and Technical Information of China (English)

    Hong Wu; Claus Moser; Heng-Zhuang Wang; Niels Hiby; Zhi-Jun Song

    2015-01-01

    Formation of biofilm is a survival strategy for bacteria and fungi to adapt to their living environment, especially in the hostile environment. Under the protection of biofilm, microbial cells in biofilm become tolerant and resistant to antibiotics and the immune responses, which increases the difficulties for the clinical treatment of biofilm infections. Clinical and laboratory investigations demonstrated a perspicuous correlation between biofilm infection and medical foreign bodies or indwelling devices. Clinical observations and experimental studies indicated clearly that antibiotic treatment alone is in most cases insufficient to eradicate biofilm infections. Therefore, to effectively treat biofilm infections with currently available antibiotics and evaluate the outcomes become important and urgent for clinicians. The review summarizes the latest progress in treatment of clinical biofilm infections and scientific investigations, discusses the diagnosis and treatment of different biofilm infections and introduces the promising laboratory progress, which may contribute to prevention or cure of biofilm infections. We conclude that, an efficient treatment of biofilm infections needs a well-established multidisciplinary collaboration, which includes removal of the infected foreign bodies, selection of biofilm-active, sensitive and well-penetrating antibiotics, systemic or topical antibiotic administration in high dosage and combinations, and administration of anti-quorum sensing or biofilm dispersal agents.

  4. Anthranilate deteriorates the structure of Pseudomonas aeruginosa biofilms and antagonizes the biofilm-enhancing indole effect.

    Science.gov (United States)

    Kim, Soo-Kyoung; Park, Ha-Young; Lee, Joon-Hee

    2015-04-01

    Anthranilate and indole are alternative degradation products of tryptophan, depending on the bacterial species. While indole enhances the biofilm formation of Pseudomonas aeruginosa, we found that anthranilate, the tryptophan degradation product of P. aeruginosa, had an opposite effect on P. aeruginosa biofilm formation, in which anthranilate deteriorated the mushroom structure of biofilm. The anthranilate effect on biofilm formation was differentially exerted depending on the developmental stage and the presence of shear force. Anthranilate slightly accelerated the initial attachment of P. aeruginosa at the early stage of biofilm development and appeared to build more biofilm without shear force. But anthranilate weakened the biofilm structure in the late stage, deteriorating the mushroom structure of biofilms with shear force to make a flat biofilm. To investigate the interplay of anthranilate with indole in biofilm formation, biofilms were cotreated with anthranilate and indole, and the results showed that anthranilate antagonized the biofilm-enhancing effect of indole. Anthranilate was able to deteriorate the preformed biofilm. The effect of anthranilate and indole on biofilm formation was quorum sensing independent. AntR, a regulator of anthranilate-degrading metabolism was synergistically activated by cotreatment with anthranilate and indole, suggesting that indole might enhance biofilm formation by facilitating the degradation of anthranilate. Anthranilate slightly but significantly affected the cyclic diguaniylate (c-di-GMP) level and transcription of major extracellular polysaccharide (Psl, Pel, and alginate) operons. These results suggest that anthranilate may be a promising antibiofilm agent and antagonize the effect of indole on P. aeruginosa biofilm formation.

  5. STUDY OF ULTRASOUND RADIATION INFLUENCE ON ABILITY TO FORM BIOFILMS AND FORMED BIOFILMS OF KLEBSIELLA PNEUMONIAE

    OpenAIRE

    Mozgova Yu.A.

    2013-01-01

    With aim to detect ability to form biofilms in K.pneumoniae and to study effects of low-intensity ultrasound radiation on formed biofilms and their aggregation microbiological research of material frompatients with pyoinflammatory diseases was performed. It was found that low-intensity ultrasound radiation could destroy formed biofilms of K. pneumoniae and decrease ability of this pathogen to form secondary biofilms.

  6. Biological nitrogen removal in one step by nitritation and anaerobic oxidation of ammonia in biofilms; Einstufige biologische Stickstoffelimination durch Nitritation und anaerobe Ammonium-Oxidation im Biofilm

    Energy Technology Data Exchange (ETDEWEB)

    Helmer, C.; Tromm, C.; Hippen, A.; Rosenwinkel, K.H.; Seyfried, C.F.; Kunst, S. [Hannover Univ. (Germany). Inst. fuer Siedlungswasserwirtschaft und Abfalltechnik

    1999-07-01

    oxidation in the deeper part of the biofilm. (orig.) [German] Fuer die Behandlung hoch stickstoffhaltiger Abwaesser mit niedrigem C/N-Verhaeltnis sind autotrophe Mikroorganismen, die Ammonium direkt in elementaren Stickstoff umsetzen, besonders interessant. Ihre Verbreitung und Bedeutung in den Mischbiozoenosen grosstechnischer Abwasserreinigungsanlagen einzuschaetzen bzw. nachzuweisen, ist ausserordentlich schwierig. So konnte bislang nicht abschliessend geklaert werden, auf welche Reaktionen die einstufige Stickstoffelimination, hier als Deammonifikation bezeichnet, in der Nitrifikationsstufe (Scheibentauchkoerper) der Sickerwasserreinigungsanlage Mechernich zurueckgefuehrt werden kann. Zwischenzeitlich ist es gelungen, die Deammonifikation in einer Versuchsanlage nach dem Moving Bed-Verfahren zu etablieren. In Batchversuchen mit den bewachsenen Aufwuchstraegern konnten erstmals die Stickstoffumsetzungen am intakten Biofilm untersucht werden. Abhaengig von der Sauerstoffkonzentration liessen sich zwei autotrophe stickstoffumsetzende Reaktionen im Biofilm nachweisen: Eine Nitritation unter aeroben Bedingungen und eine anaerobe Ammonium-Oxidation. Bei der anaeroben Ammonium-Oxidation wurde Ammonium als Elektronendonator mit Nitrit als Elektronenakzeptor umgesetzt. Endprodukt der Reaktion war N{sub 2}. Ammonium und Nitrit reagierten in einem stoechiometrischen Verhaeltnis von 1:1,37, das in gleicher Groessenordnung fuer den ANAMMOX-Prozess beschrieben ist (1:1,31 {+-} 0,06). Nitrat konnte nicht als Elektronenakzeptor fuer die Reaktion genutzt werden. Fuer die sauerstoffunabhaengige Oxidation von Ammonium musste der Reaktionspartner Nitrit jeweils vorgelegt werden. Ueber die Sauerstoffkonzentration im umgebenden Medium liessen sich die Anteile der Nitritation und der anaeroben Ammonium-Oxidation am Stickstoffumsatz im Biofilm steuern. Bei einer Sauerstoffkonzentration von 0,7 mg/l standen beide Prozesse im Gleichgewicht, so dass eine direkte, nahezu vollstaendige Elimination

  7. Candida Biofilms: Development, Architecture, and Resistance.

    Science.gov (United States)

    Chandra, Jyotsna; Mukherjee, Pranab K

    2015-08-01

    Intravascular device-related infections are often associated with biofilms (microbial communities encased within a polysaccharide-rich extracellular matrix) formed by pathogens on the surfaces of these devices. Candida species are the most common fungi isolated from catheter-, denture-, and voice prosthesis-associated infections and also are commonly isolated from contact lens-related infections (e.g., fungal keratitis). These biofilms exhibit decreased susceptibility to most antimicrobial agents, which contributes to the persistence of infection. Recent technological advances have facilitated the development of novel approaches to investigate the formation of biofilms and identify specific markers for biofilms. These studies have provided extensive knowledge of the effect of different variables, including growth time, nutrients, and physiological conditions, on biofilm formation, morphology, and architecture. In this article, we will focus on fungal biofilms (mainly Candida biofilms) and provide an update on the development, architecture, and resistance mechanisms of biofilms.

  8. D-amino acids trigger biofilm disassembly.

    Science.gov (United States)

    Kolodkin-Gal, Ilana; Romero, Diego; Cao, Shugeng; Clardy, Jon; Kolter, Roberto; Losick, Richard

    2010-04-30

    Bacteria form communities known as biofilms, which disassemble over time. In our studies outlined here, we found that, before biofilm disassembly, Bacillus subtilis produced a factor that prevented biofilm formation and could break down existing biofilms. The factor was shown to be a mixture of D-leucine, D-methionine, D-tyrosine, and D-tryptophan that could act at nanomolar concentrations. D-amino acid treatment caused the release of amyloid fibers that linked cells in the biofilm together. Mutants able to form biofilms in the presence of D-amino acids contained alterations in a protein (YqxM) required for the formation and anchoring of the fibers to the cell. D-amino acids also prevented biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa. D-amino acids are produced by many bacteria and, thus, may be a widespread signal for biofilm disassembly. PMID:20431016

  9. Investigating Biofilm Recalcitrance In Pipe Flow Systems

    Science.gov (United States)

    Aggarwal, S.; Stewart, P. S.; Hozalski, R. M.

    2015-12-01

    It is challenging to remove biofilms from pipe walls owing to their recalcitrant nature. Several physiological explanations resulting from the community existence of microbes have been offered to explain the recalcitrant nature of biofilms. Herein a biophysical aspect of biofilm recalcitrance is being reported. While optimal efficiency argument suggests that bacterial biofilms would be just strong enough to withstand the surrounding shear forces, our experimental findings reveal the biofilms to be at least 330 to 55000 times stronger. Additionally, Monte-Carlo simulations for biofilm detachment in drinking water systems were performed, which show that the existing flow velocities are insufficient for significant biofilm removal and warrant alternative detachment strategies. This emphasizes the importance of considering strategies for biofilm weakening (and subsequent detachment) in conjunction with or as an alternative to bacterial inactivation.

  10. Mechanical properties and disruption of dental biofilms

    OpenAIRE

    Rmaile, Amir

    2013-01-01

    A literature review of dental plaque biofilms formation, progression and detachment mechanisms is presented in this thesis. Various strategies that have been employed to reduce or eliminate dental biofilms are discussed. The focus of the thesis was on the mechanical properties and disruption of dental biofilms, especially from hard-to-access areas of the oral cavity, such as the interproximal (IP) sites between the teeth. Various methods to measure mechanical properties of dental biofilms wer...

  11. Bioinspired, Dynamic, Structured Surfaces for Biofilm Prevention

    OpenAIRE

    Epstein, Alexander

    2012-01-01

    Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even l...

  12. Strategies for combating bacterial biofilm infections

    DEFF Research Database (Denmark)

    Wu, Hong; Moser, Claus Ernst; Wang, Heng-Zhuang;

    2015-01-01

    Formation of biofilm is a survival strategy for bacteria and fungi to adapt to their living environment, especially in the hostile environment. Under the protection of biofilm, microbial cells in biofilm become tolerant and resistant to antibiotics and the immune responses, which increases...

  13. Microbiële biofilms in tandheelkunde

    NARCIS (Netherlands)

    B.P. Krom

    2015-01-01

    Aangehechte gemeenschappen van micro-organismen, ook wel biofilms genoemd, zijn altijd en overal aanwezig. Hoewel biofilms een slechte naam hebben, zijn ze meestal natuurlijk, gezond en zelfs gewenst. In de tandartspraktijk komen zowel gezonde (orale biofilms) als ongezonde (bijv. in de waterleiding

  14. Microbiële biofilms in tandheelkunde

    NARCIS (Netherlands)

    B.P. Krom

    2015-01-01

    Aangehechte gemeenschappen van micro-organismen, ook wel biofilms genoemd, zijn altijd en overal aanwezig. Hoewel biofilms een slechte naam hebben, zijn ze meestal natuurlijk, gezond en zelfs gewenst. In de mondzorgpraktijk komen zowel gezonde (orale biofilms) als ongezonde (bijv. in de waterleiding

  15. Natural biofilm formation with Legionella pneumophila.

    Science.gov (United States)

    Portier, Emilie; Héchard, Yann

    2013-01-01

    Biofilm formation could be studied in various conditions. Most of the studies with Legionella pneumophila used monospecies biofilm in culture media. In some cases, it is important to study bacteria in conditions more close to environmental conditions. In this paper, we describe protocols to produce natural biofilms from river water that were spiked with L. pneumophila. PMID:23150397

  16. Extracellular DNA in oral microbial biofilms.

    Science.gov (United States)

    Jakubovics, Nicholas S; Burgess, J Grant

    2015-07-01

    The extracellular matrix of microbial biofilms is critical for surface adhesion and nutrient homeostasis. Evidence is accumulating that extracellular DNA plays a number of important roles in biofilm integrity and formation on hard and soft tissues in the oral cavity. Here, we summarise recent developments in the field and consider the potential of targeting DNA for oral biofilm control.

  17. Small molecule control of bacterial biofilms.

    Science.gov (United States)

    Worthington, Roberta J; Richards, Justin J; Melander, Christian

    2012-10-01

    Bacterial biofilms are defined as a surface attached community of bacteria embedded in a matrix of extracellular polymeric substances that they have produced. When in the biofilm state, bacteria are more resistant to antibiotics and the host immune response than are their planktonic counterparts. Biofilms are increasingly recognized as being significant in human disease, accounting for 80% of bacterial infections in the body and diseases associated with bacterial biofilms include: lung infections of cystic fibrosis patients, colitis, urethritis, conjunctivitis, otitis, endocarditis and periodontitis. Additionally, biofilm infections of indwelling medical devices are of particular concern, as once the device is colonized infection is virtually impossible to eradicate. Given the prominence of biofilms in infectious diseases, there has been an increased effort toward the development of small molecules that will modulate bacterial biofilm development and maintenance. In this review, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms through non-microbicidal mechanisms. The review discuses the numerous approaches that have been applied to the discovery of lead small molecules that mediate biofilm development. These approaches are grouped into: (1) the identification and development of small molecules that target one of the bacterial signaling pathways involved in biofilm regulation, (2) chemical library screening for compounds with anti-biofilm activity, and (3) the identification of natural products that possess anti-biofilm activity, and the chemical manipulation of these natural products to obtain analogues with increased activity. PMID:22733439

  18. Implications of bacterial biofilms in chronic rhinosinusitis

    Directory of Open Access Journals (Sweden)

    Edwin Tamashiro

    2009-06-01

    Full Text Available The recognition of sessile form of bacteria with particular features, known as biofilm, has given new insights to the understanding of pathogenesis of several chronic diseases, including Chronic Rhinosinusitis (CRS. In this article we review the main characteristics of biofilms, describe the current methods used to demonstrate biofilms in chronic rhinosinusitis and discuss the future directions of research in the field.

  19. Confocal Microscopy Imaging of the Biofilm Matrix

    DEFF Research Database (Denmark)

    Schlafer, Sebastian; Meyer, Rikke Louise

    2016-01-01

    The extracellular matrix is an integral part of microbial biofilms and an important field of research. Confocal laser scanning microscopy is a valuable tool for the study of biofilms, and in particular of the biofilm matrix, as it allows real-time visualization of fully hydrated, living specimens...

  20. Presence of extracellular DNA in the Candida albicans biofilm matrix and its contribution to biofilms.

    Science.gov (United States)

    Martins, Margarida; Uppuluri, Priya; Thomas, Derek P; Cleary, Ian A; Henriques, Mariana; Lopez-Ribot, José L; Oliveira, Rosário

    2010-05-01

    DNA has been described as a structural component of the extracellular matrix (ECM) in bacterial biofilms. In Candida albicans, there is a scarce knowledge concerning the contribution of extracellular DNA (eDNA) to biofilm matrix and overall structure. This work examined the presence and quantified the amount of eDNA in C. albicans biofilm ECM and the effect of DNase treatment and the addition of exogenous DNA on C. albicans biofilm development as indicators of a role for eDNA in biofilm development. We were able to detect the accumulation of eDNA in biofilm ECM extracted from C. albicans biofilms formed under conditions of flow, although the quantity of eDNA detected differed according to growth conditions, in particular with regards to the medium used to grow the biofilms. Experiments with C. albicans biofilms formed statically using a microtiter plate model indicated that the addition of exogenous DNA (>160 ng/ml) increases biofilm biomass and, conversely, DNase treatment (>0.03 mg/ml) decreases biofilm biomass at later time points of biofilm development. We present evidence for the role of eDNA in C. albicans biofilm structure and formation, consistent with eDNA being a key element of the ECM in mature C. albicans biofilms and playing a predominant role in biofilm structural integrity and maintenance.

  1. Demenz und Depression bei Patienten mit idiopathischem Parkinson-Syndrom

    Directory of Open Access Journals (Sweden)

    Herting B

    2007-01-01

    Full Text Available Das idiopathische Parkinson-Syndrom (IPS ist eine progressive neurodegenerative Erkrankung mit motorischen und nicht-motorischen Symptomen. Bei Patienten mit IPS sind kognitive Defizite und Demenzen mit einer Prävalenz von 20–40 % nachgewiesen worden. Risikofaktoren für das Auftreten einer Parkinson-Demenz (PDe sind hohes Alter bei Krankheitsbeginn, schwere und/oder beidseitige motorische Symptomatik, Verwirrtheitszustände unter Levodopa-Medikation, aber auch Demenzerkrankungen in der Familie und niedriges Bildungsniveau. Patienten mit PDe weisen eine erhöhte Morbidität und Mortalität im Vergleich zu Patienten mit IPS ohne Demenz und der altersgleichen Normalbevölkerung auf, die unabhängig von der Schwere der motorischen Einbußen zweifach erhöht ist. Die Depression ist das häufigste psychiatrische Symptom beim IPS (die Angaben zur Prävalenz schwanken zwischen 4 % und 70 % und beeinflußt neben den Aktivitäten des täglichen Lebens wesentlich die Lebensqualität der Betroffenen. Darin liegt auch die Herausforderung, kognitive und affektive Symptome effizient zu behandeln.

  2. The micro turbine: the MIT example; La micro turbine: l'exemple du MIT

    Energy Technology Data Exchange (ETDEWEB)

    Ribaud, Y. [Office National d' Etudes et de Recherches Aerospatiales (ONERA-DEFA), 92 - Chatillon (France)

    2001-10-01

    The micro turbine study began a few years ago at the MIT, with the participation of specialists from different fields. The purpose is the development of a MEMS (micro electro mechanical systems) based, 1 cm in diameter, micro gas turbine. Potential applications are devoted to micro drone propulsion, electric power generation for portable power sources in order to replace heavy Lithium batteries, satellite motorization, the surface distributed power for boundary suction on plane wings. The manufacturing constraints at such small scales lead to 2-D extruded shapes. The physical constraints stem from viscous effects and from limitations given by 2-D geometry. The time scales are generally shorter than for conventional machines. Otherwise the material properties are better at such length scales. Transposition from conventional turbomachinery laws is no more applicable and new design methods must be established. The present paper highlights the project progress and the technology breakthroughs. (author)

  3. Synergistic Interactions in Multispecies Biofilms

    DEFF Research Database (Denmark)

    Ren, Dawei

    The coexistence of hugely diverse microbes in most environments highlights the intricate interactions in microbial communities, which are central to their properties, such as productivity, stability and the resilience to disturbance. Biofilm, in environmental habitats, is such a spatially...... multispecies biofilm models, oral microbial community, also known as “dental plaque” is thoroughly investigated as a focal point to describe the interspecies interactions [1]. However, owing to the lack of a reliable high throughput and quantitative approach for exploring the interplay between multiple...... bacterial species, the study to elucidate the impact of interaction networks on the multispecies biofilms in natural ecosystems, especially in soil, is still at an early stage. The diverse patterns of interactions within the mixed communities as well as the predatorprey relationship between protozoa...

  4. Microbial pathogenesis and biofilm development

    DEFF Research Database (Denmark)

    Reisner, A.; Høiby, N.; Tolker-Nielsen, Tim;

    2004-01-01

    cycles of different microorganisms will eventually lead to improved treatments. Several bacteria have evolved specific strategies for virulent colonization of humans in addition to their otherwise harmless establishment as environmental inhabitants. In many such cases biofilm development seems to play...... permit bacterial growth to occur. In laboratory model systems the growth of the surface-associated bacteria is supported by the nutrient supply in the moving or standing liquid. A benchmark of biofilm formation by several organisms in vitro is the development of three-dimensional structures that have...... been termed 'maturation', which is thought to be mediated by a differentiation process. Maturation into late stages of biofilm development resulting in stable and robust structures may require the formation of a matrix of extracellular polymeric substances (EPS), which are most often assumed to consist...

  5. Biofilmes e Lentes de Contacto

    OpenAIRE

    Silva, Ana Rita Baptista da

    2012-01-01

    O Biofilme pode ser designado como um grupo funcional de microrganismos aderidos a uma superfície estando envolvidos numa matriz exopolimérica. As bactérias organizam-se em Biofilmes, devido a, quando não estão organizadas em microcolónias terem reduzida taxa de sobrevivência. A estrutura e formação destes filmes são heterogéneas, integrando em si nichos de bactérias com graus de crescimento distintos. O estudo da relação dos Biofilmes com as lentes de contacto é pertinente, pois estas são...

  6. Islam, Migration und Integration: Konflikte jugendlicher Migranten mit islamischem Hintergrund

    Directory of Open Access Journals (Sweden)

    Ilhan Kizilhan

    2008-04-01

    Full Text Available Der Islam mit seinen verschiedenen Verhaltensweisen und Verboten spielt direkt oder indirekt immer noch eine wichtige Rolle im alltäglichen Leben vieler Migranten. Religiöse Vorschriften zeichnen sich dadurch aus, dass ihrer Achtung nicht juristisch, sondern durch sozialen Druck Nachdruck verliehen wird (Verwandtschaft, religiöse Lehrer, islamische Gemeinde, religiöse Vereine etc. und dass ihre Missachtung mit Folgen in Form von Ausgrenzung, Missachtung und Diskriminierung einhergeht. Die kulturellen Vorstellungen der ersten Generation unterscheiden sich auf Grund der unterschiedlichen Biografien von denen der zweiten und dritten durch den Grad der Verwurzelung in der kulturellen Identität und der Verbundenheit mit traditionellen Wertvorstellungen. Fehlende Integrationskonzepte, Ausgrenzung im Migrationsland auf der einen und weltweite staatliche und halbstaatliche Konflikte im Namen des Islams bis hin zum Terrorismus auf der anderen Seite haben einen erheblichen Einfluss auf den Integrationsgrad von jugendlichen Migranten im Aufnahmeland.

  7. Professionell entwickeln mit Java EE 7 das umfassende Handbuch

    CERN Document Server

    Salvanos, Alexander

    2014-01-01

    Ein praxisorientiertes Lehrbuch zur JEE 7 und zugleich ein Standardwerk, das Sie auf Ihrem Weg zum Enterprise-Entwickler begleitet. Inklusive Best Practices für leichtgewichtige Enterprise Applications, Standards zu servicebasierten Anwendungen, Persistence API, Dependency Injection, HTML5 und Performance-Tuning. Aus dem Inhalt: Grundlagen und Installation Software-Architektur mit Java EE Webanwendungen mit HTML5 und CSS3 Java Standard Tag Library Asynchrone Servlets und Non-blocking I/O Datenbanken anbinden mit der JDBC API Java Server Faces Datenbank-Organisation Java Persistence API Objektrelationales Mapping Transaktionssicherheit Performance-Tuning Internationalisierung Enterprise Java Beans WebSockets PrimeFaces Deployment Galileo Press heißt von jetzt an Rheinwerk Verlag.

  8. Pattern formation in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Parsek, Matthew R.; Tolker-Nielsen, Tim

    2008-01-01

    Bacteria are capable of forming elaborate multicellular communities called biofilms. Pattern formation in biofilms depends on cell proliferation and cellular migration in response to the available nutrients and other external cues, as well as on self-generated intercellular signal molecules...... and the production of an extracellular matrix that serves as a structural 'scaffolding' for the biofilm cells. Pattern formation in biofilms allows cells to position themselves favorably within nutrient gradients and enables buildup and maintenance of physiologically distinct subpopulations, which facilitates...... survival of one or more subpopulations upon environmental insult, and therefore plays an important role in the innate tolerance displayed by biofilms toward adverse conditions....

  9. Growing and Analyzing Biofilms in Flow Chambers

    DEFF Research Database (Denmark)

    Tolker-Nielsen, Tim; Sternberg, Claus

    2011-01-01

    This unit describes the setup of flow chamber systems for the study of microbial biofilms, and methods for the analysis of structural biofilm formation. Use of flow chambers allows direct microscopic investigation of biofilm formation. The biofilms in flow chambers develop under hydrodynamic......, and disassembly and cleaning of the system. In addition, embedding and fluorescent in situ hybridization of flow chamber–grown biofilms are addressed. Curr. Protoc. Microbiol. 21:1B.2.1-1B.2.17. © 2011 by John Wiley & Sons, Inc....

  10. D-Amino Acids Trigger Biofilm Disassembly

    OpenAIRE

    Kolodkin-Gal, Illana; Romero, Diego; Cao, Shugeng; Clardy, Jon; Kolter, Roberto; Losick, Richard

    2010-01-01

    Bacteria form communities known as biofilms, which disassemble over time. Here we found that prior to biofilm disassembly Bacillus subtilis produced a factor that prevented biofilm formation and could break down existing biofilms. The factor was shown to be a mixture of D-leucine, D-methionine, D-tyrosine and D-tryptophan that could act at nanomolar concentrations. D-amino acid treatment caused the release of amyloid fibers that linked cells in the biofilm together. Mutants able to form biofi...

  11. The roles of biofilm matrix polysaccharide Psl in mucoid Pseudomonas aeruginosa biofilms.

    Science.gov (United States)

    Ma, Luyan; Wang, Shiwei; Wang, Di; Parsek, Matthew R; Wozniak, Daniel J

    2012-07-01

    The opportunistic pathogen Pseudomonas aeruginosa causes life-threatening, persistent infections in patients with cystic fibrosis (CF). Persistence is attributed to the ability of these bacteria to form structured communities (biofilms). Biofilms rely on an extracellular polymeric substances matrix to maintain structure. Psl exopolysaccharide is a key matrix component of nonmucoid biofilms, yet the role of Psl in mucoid biofilms is unknown. In this report, using a variety of mutants in a mucoid P. aeruginosa background, we found that deletion of Psl-encoding genes dramatically decreased their biofilm formation ability, indicating that Psl is also a critical matrix component of mucoid biofilms. Our data also suggest that the overproduction of alginate leads to mucoid biofilms, which occupy more space, whereas Psl-dependent biofilms are densely packed. These data suggest that Psl polysaccharide may have significant contributions in biofilm persistence in patients with CF and may be helpful for designing therapies for P. aeruginosa CF infection.

  12. Wege zu einem nachhaltigen Umgang mit Süßwasser

    OpenAIRE

    Wissenschaftlicher Beirat Globale Umweltveränderungen

    2009-01-01

    Der Umgang mit Wasser – seine Erschließung, Verteilung, Nutzung, Reinhaltung und Abwehr – hat die Geschichte der menschlichen Zivilisation nachhaltig geprägt. Der Umgang mit Wasser ist aber auch eine der vorrangigen Aufgaben der Gegenwart. Heute leben rund 2 Mrd. Menschen ohne Zugang zu sauberem Trink- und Sanitärwasser (Gleick, 1993), weltweit werden nur 5% der Abwässer gereinigt. Infolgedessen leidet jeder zweite Mensch in den Entwicklungsländern an einer wasserbedingten Krankheit; 5 Mio. M...

  13. Mikrostrukturierte segmentierte Paul-Falle mit einstellbarem Magnetfeldgradienten

    OpenAIRE

    Kaufmann, Delia

    2012-01-01

    Lasergekühlte Ionenketten in mikrostrukturierten Paul-Fallen (Mikrofallen) bieten ein großes Potential für Anwendungen in den Quanteninformationswissenschaften. Sie können in einer dekohärenzarmen Umgebung präpariert und manipuliert, und ihre Zustände mit einer Effizienz von fast 100% detektiert werden. Mit zusätzlichen Magnetfeldgradienten ist es möglich, die Ionen im Frequenzraum zu adressieren und zu koppeln (MAGIC-Methode - MAgnetic Gradient Induced Coupling). In dieser Arbeit wurde ei...

  14. Enantioselektive katalytische Hydrierung mit polymerfixiertem Katalysator auf einer Kieselgurmatrix

    OpenAIRE

    Jaser, Karl

    2004-01-01

    Diese Arbeit beschäftigt sich mit der Fixierung des enantioselektiven Rhodium-Pyrphos-Katalysators auf einer inerten Kieselgurmatrix. Dabei wird als Polymer Glycerin-tris[polypropylenglycol-amingestoppt]-ether verwendet, das mit 1,3,5-Benzoltricarbonsäure-trichlorid oder 1,6-Diisocyanato-hexan vernetzt wird. Die Hydrierdauer einer bestimmten Menge Acetamidozimtsäure, der Umsatz und der ee-Wert, die im Batch-Betrieb ermittelt wurden, lassen einen Rückschluss auf die Menge des reaktiven Rhodium...

  15. Combining Biofilm-Controlling Compounds and Antibiotics as a Promising New Way to Control Biofilm Infections

    Directory of Open Access Journals (Sweden)

    Andréia Bergamo Estrela

    2010-05-01

    Full Text Available Many bacteria grow on surfaces forming biofilms. In this structure, they are well protected and often high dosages of antibiotics cannot clear infectious biofilms. The formation and stabilization of biofilms are mediated by diffusible autoinducers (e.g. N-acyl homoserine lactones, small peptides, furanosyl borate diester. Metabolites interfering with this process have been identified in plants, animals and microbes, and synthetic analogues are known. Additionally, this seems to be not the only way to control biofilms. Enzymes capable of cleaving essential components of the biofilm matrix, e.g. polysaccharides or extracellular DNA, and thus weakening the biofilm architecture have been identified. Bacteria also have mechanisms to dissolve their biofilms and return to planktonic lifestyle. Only a few compounds responsible for the signalling of these processes are known, but they may open a completely novel line of biofilm control. All these approaches lead to the destruction of the biofilm but not the killing of the pathogens. Therefore, a combination of biofilm-destroying compounds and antibiotics to handle biofilm infections is proposed. In this article, different approaches to combine biofilm-controlling compounds and antibiotics to fight biofilm infections are discussed, as well as the balance between biofilm formation and virulence.

  16. Biofilm induced tolerance towards antimicrobial peptides.

    Directory of Open Access Journals (Sweden)

    Anders Folkesson

    Full Text Available Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically regulated tolerant subpopulation formation and not caused by a general biofilm property. No significant difference in survival was detected when the strains were challenged with ciprofloxacin. Our data show that biofilm formation confers increased colistin tolerance to cells within the biofilm structure, but the protection is conditional being dependent on the structural organization of the biofilm, and the induction of specific tolerance mechanisms.

  17. The clinical impact of bacterial biofilms

    DEFF Research Database (Denmark)

    Høiby, Niels; Ciofu, Oana; Johansen, Helle Krogh;

    2011-01-01

    Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria (and fungi) are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA....... Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation....... Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity...

  18. The immune system vs. Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Jensen, Peter Østrup; Givskov, Michael; Bjarnsholt, Thomas;

    2010-01-01

    in the planktonic state. Accordingly, much less is known about the immune responses to the presence of biofilm-based infections (which is probably also due to the relatively short period of time in which the immune response to biofilms has been studied). Nevertheless, more recent in vivo and in vitro studies have...... revealed both innate as well as adaptive immune responses to biofilms. On the other hand, measures launched by biofilm bacteria to achieve protection against the various immune responses have also been demonstrated. Whether particular immune responses to biofilm infections exist remains to be firmly...... established. However, because biofilm infections are often persistent (or chronic), an odd situation appears with the simultaneous activation of both arms of the host immune response, neither of which can eliminate the biofilm pathogen, but instead, in synergy, causes collateral tissue damage. Although...

  19. Biofilm Induced Tolerance Towards Antimicrobial Peptides

    DEFF Research Database (Denmark)

    Folkesson, Anders; Haagensen, Janus Anders Juul; Zampaloni, Claudia;

    2008-01-01

    Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due...... to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics...... of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically...

  20. Vibrio cholerae Biofilms and Cholera Pathogenesis.

    Directory of Open Access Journals (Sweden)

    Anisia J Silva

    2016-02-01

    Full Text Available Vibrio cholerae can switch between motile and biofilm lifestyles. The last decades have been marked by a remarkable increase in our knowledge of the structure, regulation, and function of biofilms formed under laboratory conditions. Evidence has grown suggesting that V. cholerae can form biofilm-like aggregates during infection that could play a critical role in pathogenesis and disease transmission. However, the structure and regulation of biofilms formed during infection, as well as their role in intestinal colonization and virulence, remains poorly understood. Here, we review (i the evidence for biofilm formation during infection, (ii the coordinate regulation of biofilm and virulence gene expression, and (iii the host signals that favor V. cholerae transitions between alternative lifestyles during intestinal colonization, and (iv we discuss a model for the role of V. cholerae biofilms in pathogenicity.

  1. Modelling the growth of a methanotrophic biofilm

    DEFF Research Database (Denmark)

    Arcangeli, J.-P.; Arvin, E.

    1999-01-01

    This article discusses the growth of methanotrophic biofilms. Several independent biofilm growths scenarios involving different inocula were examined. Biofilm growth, substrate removal and product formation were monitored throughout the experiments. Based on the oxygen consumption it was concluded...... that heterotrophs and nitrifiers co-existed with methanotrophs in the biofilm. Heterotrophic biomass grew on soluble polymers formed by the hydrolysis of dead biomass entrapped in the biofilm. Nitrifier populations developed because of the presence of ammonia in the mineral medium. Based on these experimental...... was performed on this model. It indicated that the most influential parameters were those related to the biofilm (i.e. density; solid-volume fraction; thickness). This suggests that in order to improve the model, further research regarding the biofilm structure and composition is needed....

  2. Molecular Basis for Saccharomyces cerevisiae Biofilm Development

    DEFF Research Database (Denmark)

    Andersen, Kaj Scherz

    In this study, I sought to identify genes regulating the global molecular program for development of sessile multicellular communities, also known as biofilm, of the eukaryotic microorganism, Saccharomyces cerevisiae (yeast). Yeast biofilm has a clinical interest, as biofilms can cause chronic...... infections in humans. Biofilm is also interesting from an evolutionary standpoint, as an example of primitive multicellularity. By using a genome-wide screen of yeast deletion mutants, I show that 71 genes are essential for biofilm formation. Two-thirds of these genes are required for transcription of FLO11......, but only a small subset is previously described as regulators of FLO11. These results reveal that the regulation of biofilm formation and FLO11 is even more complex than what has previously been described. I find that the molecular program for biofilm formation shares many essential components with two...

  3. Cell death in Pseudomonas aeruginosa biofilm development

    DEFF Research Database (Denmark)

    Webb, J.S.; Thompson, L.S.; James, S.;

    2003-01-01

    Bacteria growing in biofilms often develop multicellular, three-dimensional structures known as microcolonies. Complex differentiation within biofilms of Pseudomonas aeruginosa occurs, leading to the creation of voids inside microcolonies and to the dispersal of cells from within these voids....... However, key developmental processes regulating these events are poorly understood. A normal component of multicellular development is cell death. Here we report that a repeatable pattern of cell death and lysis occurs in biofilms of P. aeruginosa during the normal course of development. Cell death...... occurred with temporal and spatial organization within biofilms, inside microcolonies, when the biofilms were allowed to develop in continuous-culture flow cells. A subpopulation of viable cells was always observed in these regions. During the onset of biofilm killing and during biofilm development...

  4. Biofilms: an emergent form of bacterial life.

    Science.gov (United States)

    Flemming, Hans-Curt; Wingender, Jost; Szewzyk, Ulrich; Steinberg, Peter; Rice, Scott A; Kjelleberg, Staffan

    2016-08-11

    Bacterial biofilms are formed by communities that are embedded in a self-produced matrix of extracellular polymeric substances (EPS). Importantly, bacteria in biofilms exhibit a set of 'emergent properties' that differ substantially from free-living bacterial cells. In this Review, we consider the fundamental role of the biofilm matrix in establishing the emergent properties of biofilms, describing how the characteristic features of biofilms - such as social cooperation, resource capture and enhanced survival of exposure to antimicrobials - all rely on the structural and functional properties of the matrix. Finally, we highlight the value of an ecological perspective in the study of the emergent properties of biofilms, which enables an appreciation of the ecological success of biofilms as habitat formers and, more generally, as a bacterial lifestyle. PMID:27510863

  5. Biofilm monitoring using complex permittivity.

    Energy Technology Data Exchange (ETDEWEB)

    Altman, Susan Jeanne; McGrath, Lucas K.; Dolan, Patricia L.; Yelton, William Graham

    2008-10-01

    There is strong interest in the detection and monitoring of bio-fouling. Bio-fouling problems are common in numerous water treatments systems, medical and dental apparatus and food processing equipment. Current bio-fouling control protocols are time consuming and costly. New early detection techniques to monitor bio-forming contaminates are means to enhanced efficiency. Understanding the unique dielectric properties of biofilm development, colony forming bacteria and nutrient background will provide a basis to the effectiveness of controlling or preventing biofilm growth. Dielectric spectroscopy measurements provide values of complex permittivity, {var_epsilon}*, of biofilm formation by applying a weak alternating electric field at various frequencies. The dielectric characteristic of the biofilm, {var_epsilon}{prime}, is the real component of {var_epsilon}* and measures the biofilm's unique ability to store energy. Graphically observed dependencies of {var_epsilon}{prime} to frequency indicate dielectric relaxation or dielectric dispersion behaviors that mark the particular stage of progression during the development of biofilms. In contrast, any frequency dependency of the imaginary component, {var_epsilon}{double_prime} the loss factor, is expressed as dielectric losses from the biofilm due to dipole relaxation. The tangent angle of these two component vectors is the ratio of the imaginary component to the real component, {var_epsilon}{double_prime}/{var_epsilon}{prime} and is referred to as the loss angle tangent (tan {delta}) or dielectric loss. Changes in tan {delta} are characteristic of changes in dielectric losses during various developmental stages of the films. Permittivity scans in the above figure are of biofilm growth from P. Fluorescens (10e7 CFU's at the start). Three trends are apparent from these scans, the first being a small drop in the imaginary permittivity over a 7 hours period, best seen in the Cole-Cole plot (a). The second trend

  6. Biological nutrient removal from municipal wastewater in sequencing batch biofilm reactors

    Energy Technology Data Exchange (ETDEWEB)

    Arnz, P.

    2001-07-01

    Enhanced biological phosphorus removal (EBPR) has only been put into practice in activated sludge systems. In recent years, the Sequencing Batch Biofilm Reactor (SBBR) has emerged as an alternative allowing EBPR to be achieved in a biofilm reactor. High efficiency of phosphate removal was demonstrated in a SBBR fed with synthetic wastewater containing acetate. The aim of this study was to investigate EBPR from municipal wastewater in semi full-scale and laboratory-scale SBBRs. The focus of the investigation in the semi full-scale reactor was on determination of achievable reaction rates and effluent concentrations under varying influent conditions throughout all seasons of a year. Interactions between nitrogen and phosphorus removal and the influence of backwashing on the reactor performance was examined. Summing up, it can be stated that the SBBR proved to be an attractive alternative to activated sludge systems. Phosphorus elimination efficiency was comparable to common systems but biomass sedimentation problems were avoided. In order to further exploit the potential of the SBBR and to achieve reactor performances superior to those of existing systems designing a special biofilm carrier material may allow to increase the phenomenon of simultaneous nitrification/denitrification while maintaining EBPR activity. (orig.) [German] Die vermehrte biologische Phosphorelimination (Bio-P) aus Abwasser wurde bisher nur in Belebtschlammsystemen praktiziert. In den letzten Jahren konnte jedoch gezeigt werden, dass sich durch die Anwendung des Sequencing Batch Biofilm Reactor (SBBR) - Verfahrens auch in Biofilmreaktoren Bio-P verwirklichen laesst. Versuche in Laboranlagen haben ergeben, dass sich eine weitgehende Phosphorelimination aufrecht erhalten laesst, wenn die Reaktoren mit einem ideal zusammengesetzten, synthetischen Abwasser beschickt werden. Ziel dieser Arbeit war es, Bio-P aus kommunalem Abwasser in SBBR-Versuchsanlagen im halbtechnischen und im Labormassstab zu

  7. Biofilms in chronic infections - a matter of opportunity - monospecies biofilms in multispecies infections

    DEFF Research Database (Denmark)

    Burmølle, Mette; Thomsen, Trine Rolighed; Fazli, Mustafa;

    2010-01-01

    to permanent tissue fillers and chronic wounds) both as to distribution (such as where in the wound bed) and organization (monospecies or multispecies microcolonies). We correlate these biofilm observations to observations of commensal biofilms (dental and intestine) and biofilms in natural ecosystems (soil......). The observations of the chronic biofilm infections point toward a trend of low bacterial diversity and sovereign monospecies biofilm aggregates even though the infection in which they reside are multispecies. In contrast to this, commensal and natural biofilm aggregates contain multiple species that are believed...

  8. Zum Tragverhalten von mehrschichtigen Glaselementen mit integrierten Funktionsträgern am Beispiel von Glaslamellen mit eingebetteten Hologrammen

    OpenAIRE

    Topp, Thomas

    2008-01-01

    Glasfassaden werden neben den originären Aufgaben der Belichtung und des Gebäudeabschlusses, in zunehmendem Maße mit weiteren Funktionen ausgestattet. Die dafür notwendigen Funktionselemente sind überwiegend als Folien ausgebildet und in die Funktionsschichten von Verbundgläsern integriert. Es entstehen mehrschichtige Funktionsgläser mit einem Potenzial für Verbundtragwirkung. Die sichere Identifizierung dieses Tragverhaltens im Hinblick auf eine wirtschaftliche Dimensionierung für größere Sp...

  9. Biogenesis of Enterococcis faecium biofilms

    NARCIS (Netherlands)

    Paganelli, F.L.

    2015-01-01

    Nosocomial infections caused by Enterococcus faecium have rapidly increased worldwide and treatment options become more limited. The presence of antibiotic resistance genes and virulence factors in pathogenic E. faecium contribute to difficult-to-treat infections, frequently biofilm mediated, such a

  10. Candida biofilms: is adhesion sexy?

    Science.gov (United States)

    Soll, David R

    2008-08-26

    The development of Candida albicans biofilms requires two types of adhesion molecule - the Als proteins and Hwp1. Mutational analyses have recently revealed that these molecules play complementary roles, and their characteristics suggest that they may have evolved from primitive mating agglutinins. PMID:18727911

  11. Electrochemical impedance spectroscopy of biofilms

    Science.gov (United States)

    Microbial activity that leads to the formation of biofilms on process equipment can accelerate corrosion, reduce heat transfer rates, and generally decrease process efficiencies. Additional concerns arise in the food and pharma industries where product quality and safety are a high priority. Pharmac...

  12. Menschen mit Demenz als Interaktionspartner. Eine Auswertung empirischer Studien vor dem Hintergrund eines dimensionalisierten Interaktionsbegriffs

    OpenAIRE

    Meyer, Christian

    2014-01-01

    Der Anteil von Menschen mit Demenz an der Gesamtbevölkerung Deutschlands wird mittelfristig stark zunehmen und die Begegnung mit Betroffenen aufgrund persönlicher und familiärer Kontakte zu einem alltäglichen Teil der Gesellschaft werden. Angesichts der spezifischen Symptomatik der Demenz – insbesondere des sukzessiven Verlusts des deklarativen und biografischen (episodischen) Gedächtnisses – stellt sich die Frage, wie sich soziale Interaktion mit Menschen mit Demenz gestaltet, und ob in solc...

  13. Das Erkennen mimisch kodierter Basisemotionen durch Patienten mit Panikstörung

    OpenAIRE

    Bruckner, Julia

    2009-01-01

    Ziel unserer Untersuchung war es, Defizite der Emotionserkennung zu untersuchen und die Einflüsse auf die Emotionserkennungsfähigkeit bei Patienten mit Panikstörung zu erfassen. An der Untersuchung nahmen 37 Patienten mit Panikstörung und 43 Patienten mit leichteren neurologischen Erkrankungen teil, sie absolvierten hierbei den computergestützten FEEL-Test (Facially Expressed Emotion Labeling). Ergebnisse: Patienten mit Panikstörung weisen im Vergleich zu psychisch gesunden Kontrollp...

  14. Ein Konzept für die merkmalsbasierte Tumor-Klassifikation mit diagnostischem Ultraschall

    OpenAIRE

    Siebers, Stefan

    2008-01-01

    Die Bildgebung mit Ultraschall (Sonographie) hat sich zu der am häufigsten verwendeten medizinischen Bildgebungsmodalität entwickelt. Eine Unterscheidung gut- und bösartiger Tumoren mit Hilfe der Sonographie setzt allerdings große Erfahrung beim Untersucher voraus und gilt als außerordentlich schwierig. In dieser Arbeit wurde daher ein Konzept zur automatisierten Klassifikation mit diagnostischem Ultraschall entwickelt und im Rahmen einer klinischen Studie mit 138 Fällen zur Digni...

  15. Analyse von Arbeitsplätzen auf halbautomatischen Pflanzmaschinen mit Hilfe von MTM (Methods Time Measurement)

    OpenAIRE

    Remmele, Edgar

    2014-01-01

    Mit Hilfe von MTM (Methods Time Measurement), einem System vorbestimmter Zeiten, werden Bewegungsstudien an drei verschiedenen halbautomatischen Pflanzmaschinen durchgeführt. Hauptunterscheidungsmerkmal der untersuchten Pflanzmaschinen ist die Methode der Übergabe der Pflanze von der Pflanzperson an die Pflanzmaschine. Analysiert wird der Arbeitsplatz der Pflanzmaschine ACCORD-Standard mit der Methode Klemmscheibe, PES-Beetpflanzer 1500/1900 mit der Methode Pflanzfinger und Lännen RT-2 mit de...

  16. Interaktion mit RFID Ausleih- und Rückgabeautomaten

    DEFF Research Database (Denmark)

    Greifeneder, Elke; Heyroth, Melanie; Klingbeil, Karin;

    2011-01-01

    Der Artikel untersucht mittels Beobachtung die Interaktion zwischen RFID-Ausleih- und Rückgabeautomaten sowie Bibliotheksbenutzern in vier deutschen Bibliotheken. Die Ergebnisse belegen, dass die Interaktion grundsätzlich funktioniert. Die Benutzer zeigten Gelassenheit und Routine im Umgang mit den...

  17. Stiff lightweight steel constructions; Steife Leichtbauweise mit Stahl

    Energy Technology Data Exchange (ETDEWEB)

    Gerick, A.; Lempenauer, K. [Daimler Benz AG, Ulm (Germany). Forschungszentrum; Hauger, A.; Kopp, R. [Technische Hochschule Aachen (Germany). Inst. fuer Bildsame Formgebung

    1999-07-01

    Compared with welded sheets of composite materials, glued sheets have much better deformation characteristics. This was the result of experiments carried out by the authors. Further investigation will focus on the integration of the sheets in a car body by welding, the long-term strength of welds, the applicability of bolting or riveting techniques, and the fatigue strength of the car body under oscillating stress. [German] Durch die Verwendung von Klebefolien bzw. Klebstoffen auf Epoxidharz-Basis und einem optimierten Herstellungs- und Verarbeitungsprozess konnten im Vergleich mit geschweissten Verbundblechen erheblich groessere Umformgrade erzielt werden. Anhand von Erichsen-Tiefungen und Grenzformaenderungsschaubildern wurde dies aufgezeigt. Dabei wurde eine gute Streckzieh- und insbesonders gute Tiefziehfaehigkeit festgestellt. Mittels 4-Punkt-Biegeversuchen wurde die Gesamtbiegesteifigkeit der Verbunde ermittelt. Fuer alle Verbundvariationen wurde eine deutliche Gewichtsreduktion gegenueber Massivstahlblechen nachgewiesen. Sogar im Vergleich zu Massivaluminiumblechen lassen sich mit Streckmetallverbunden Gewichtsvorteile erreichen. Mit Hilfe der elementaren Theorie und einem Modell zur Berechnung des Traegheitsmomentes kann das tatsaechliche Biegeverhalten der Verbundstrukturen in guter Naeherung berechnet werden. Insgesamt hat sich gezeigt, dass das Ziel, umformbare und biegesteife Blechsandwiche darzustellen, mit einem geklebten Streckmetallverbundblech im Hinblick auf das genaue Anforderungsprofil weitgehend zu erreichen ist. In weiterfuehrenden Untersuchungen werden insbesondere die Anbindung an die Gesamtstruktur einer Karosserie durch Schweissverfahren, die Dauerfestigkeit von Schweissverbindungen, die Anwendbarkeit von mechanischen Fuegeverfahren (Setzverhalten von Schraub- und Nietverbindungen) und die Schwingfestigkeit des Verbundes naeher betrachtet. (orig.)

  18. Past, present and future of MIT reactor physics

    International Nuclear Information System (INIS)

    The reactor physics curriculum at MIT has been undergoing lots of changes in recent years. This paper describes the course sequence and philosophy that we have implemented and continue to develop. Additionally, thoughts on future direction with respect to modularity and web-based learning are presented. (author)

  19. Numerische Berechnung von Wirbelstromproblemen mit der Cell-Methode

    Directory of Open Access Journals (Sweden)

    K. Frenner

    2006-01-01

    Full Text Available In dieser Arbeit wird die Cell-Methode auf die quasistatischen Maxwellgleichungen angewendet. Dabei werden für die notwendige Transformation vom Primärgitter auf das duale Gitter reziproke Basisvektoren verwendet. Anhand der Felddiffusion der magnetischen Induktion in einen zylindrischen Leiter werden Ergebnisse der Cell-Methode mit einer analytischen Vergleichsrechnung präsentiert.

  20. MIT Mints a Valuable New Form of Academic Currency

    Science.gov (United States)

    Carey, Kevin

    2012-01-01

    The Massachusetts Institute of Technology (MIT) has invented or improved many world-changing things--radar, information theory, and synthetic self-replicating molecules, to name a few. Last month the university announced, to mild fanfare, an invention that could be similarly transformative, this time for higher education itself. It is called MITx.…

  1. Wie ich mich mit dem äthiopischen Regime anlegte

    DEFF Research Database (Denmark)

    Hagmann, Tobias

    2016-01-01

    Als Forscher und Kritiker der äthiopischen Politik habe ich viel über das Verhältnis gelernt, in dem Wahrheit und Macht, aber auch Moral und persönliche Interessen zueinander stehen. In den Niederungen der Realpolitik wird mit harten Bandagen um die Deutungshoheit gekämpft wird. Auch Wissenschafter...

  2. Very Short Bunches in MIT-Bates South Hall Ring

    CERN Document Server

    Wang, Dong; Farkhondeh, Manouchehr; Franklin, Wilbur; Graves, William; Ihloff, Ernie; Podobedov, Boris; Tschalär, C; Wang, Defa; Wang, Fuhua; Zwart, Townsend; van der Laan, Jan

    2005-01-01

    The study of ultra-short bunches in MIT SHR storage ring with very small momentum compactions is carried out. The ultra-short bunches are to greatly enhence the coherent radiation by many orders of magnitude. The ring lattice is resigned to reach very small momentum compaction factor down to 1·10-5

  3. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  4. Parallelization experience with four canonical econometric models using ParMitISEM

    NARCIS (Netherlands)

    Baştürk, N.; Grassi, S.; Hoogerheide, L.; van Dijk, H.K.

    2016-01-01

    This paper presents the parallel computing implementation of the MitISEM algorithm, labeled Parallel MitISEM. The basic MitISEM algorithm, introduced by Hoogerheide et al. (2012), provides an automatic and flexible method to approximate a non-elliptical target density using adaptive mixtures of Stud

  5. Chemical Biology Strategies for Biofilm Control.

    Science.gov (United States)

    Yang, Liang; Givskov, Michael

    2015-08-01

    Microbes live as densely populated multicellular surface-attached biofilm communities embedded in self-generated, extracellular polymeric substances (EPSs). EPSs serve as a scaffold for cross-linking biofilm cells and support development of biofilm architecture and functions. Biofilms can have a clear negative impact on humans, where biofilms are a common denominator in many chronic diseases in which they prime development of destructive inflammatory conditions and the failure of our immune system to efficiently cope with them. Our current assortment of antimicrobial agents cannot efficiently eradicate biofilms. For industrial applications, the removal of biofilms within production machinery in the paper and hygienic food packaging industry, cooling water circuits, and drinking water manufacturing systems can be critical for the safety and efficacy of those processes. Biofilm formation is a dynamic process that involves microbial cell migration, cell-to-cell signaling and interactions, EPS synthesis, and cell-EPS interactions. Recent progress of fundamental biofilm research has shed light on novel chemical biology strategies for biofilm control. In this article, chemical biology strategies targeting the bacterial intercellular and intracellular signaling pathways will be discussed.

  6. Diffusion in biofilms respiring on electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Renslow, Ryan S. [Washington State Univ., Pullman, WA (United States); Babauta, Jerome T. [Washington State Univ., Pullman, WA (United States); Majors, Paul D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Beyenal, Haluk [Washington State Univ., Pullman, WA (United States)

    2012-11-15

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed for noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that (1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; (2) Drs at a given location decreases with G. sulfurreducens biofilm age; (3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms—the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and (4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms.

  7. Dynamic interactions of neutrophils and biofilms

    Directory of Open Access Journals (Sweden)

    Josefine Hirschfeld

    2014-12-01

    Full Text Available Background: The majority of microbial infections in humans are biofilm-associated and difficult to treat, as biofilms are highly resistant to antimicrobial agents and protect themselves from external threats in various ways. Biofilms are tenaciously attached to surfaces and impede the ability of host defense molecules and cells to penetrate them. On the other hand, some biofilms are beneficial for the host and contain protective microorganisms. Microbes in biofilms express pathogen-associated molecular patterns and epitopes that can be recognized by innate immune cells and opsonins, leading to activation of neutrophils and other leukocytes. Neutrophils are part of the first line of defense and have multiple antimicrobial strategies allowing them to attack pathogenic biofilms. Objective/design: In this paper, interaction modes of neutrophils with biofilms are reviewed. Antimicrobial strategies of neutrophils and the counteractions of the biofilm communities, with special attention to oral biofilms, are presented. Moreover, possible adverse effects of neutrophil activity and their biofilm-promoting side effects are discussed. Results/conclusion: Biofilms are partially, but not entirely, protected against neutrophil assault, which include the processes of phagocytosis, degranulation, and formation of neutrophil extracellular traps. However, virulence factors of microorganisms, microbial composition, and properties of the extracellular matrix determine whether a biofilm and subsequent microbial spread can be controlled by neutrophils and other host defense factors. Besides, neutrophils may inadvertently contribute to the physical and ecological stability of biofilms by promoting selection of more resistant strains. Moreover, neutrophil enzymes can degrade collagen and other proteins and, as a result, cause harm to the host tissues. These parameters could be crucial factors in the onset of periodontal inflammation and the subsequent tissue breakdown.

  8. Mycobacterium biofilms: factors involved in development, dispersal, and therapeutic strategies against biofilm-relevant pathogens.

    Science.gov (United States)

    Xiang, Xiaohong; Deng, Wanyan; Liu, Minqiang; Xie, Jianping

    2014-01-01

    Many bacteria can develop biofilm (BF), a multicellular structure largely combining bacteria and their extracellular polymeric substances (EPS). The formation of biofilm results in an alternative existence in which microbes ensure their survival in adverse environments. Biofilm-relevant infections are more persistent, resistant to most antibiotics, and more recalcitrant to host immunity. Mycobacterium tuberculosis, the causative agent of tuberculosis, can develop biofilm, though whether M. tuberculosis can form biofilm within tuberculosis patients has yet to be determined. Here, we summarize the factors involved in the development and dispersal of mycobacterial biofilms, as well as underlying regulatory factors and inhibitors against biofilm to deepen our understanding of their development and to elucidate potential novel modes of action for future antibiotics. Key factors in biofilm formation identified as drug targets represent a novel and promising avenue for developing better antibiotics.

  9. Influence of biofilm thickness on micropollutants removal in nitrifying MBBRs

    DEFF Research Database (Denmark)

    Torresi, Elena; Andersen, Henrik Rasmus; Smets, Barth F.;

    The removal of pharmaceuticals was investigated in nitrifying Moving Bed Biofilm Reactors (MBBRs) containing carriers with different biofilm thicknesses. The biofilm with the thinnest thickness was found to have the highest nitrification and biotransformation rate for some key pharmaceuticals...

  10. Inhibition of Biofilm Formation Using Novel Nanostructured Surfaces Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Biofilms are ubiquitous in the environment. Few surfaces resist biofilm formation, most promote it. Biofilm formation poses problems in water systems as they can...

  11. Novel metabolic activity indicator in Streptococcus mutans biofilms

    NARCIS (Netherlands)

    D.M. Deng; M.A. Hoogenkamp; J.M. ten Cate; W. Crielaard

    2009-01-01

    Antimicrobial resistance of micro-organisms in biofilms requires novel strategies to evaluate the efficacy of caries preventive agents in actual biofilms. Hence we investigated fluorescence intensity (FI) in Streptococcus mutans biofilms constitutively expressing green fluorescent protein (GFP). Upo

  12. Microbial Biofilms in Endodontic Infections: An Update Review

    Directory of Open Access Journals (Sweden)

    Zahed Mohammadi

    2013-04-01

    Full Text Available Biofilms and microbial aggregates are the common mechanisms for the survival of bacteria in nature. In other words, the ability to form biofilms has been regarded as a virulence factor. Microbial biofilms play an essential role in several infectious diseases such as pulp and periradicular pathosis. The aim of this article was to review the adaptation mechanisms of biofilms, their roles in pulpal and periapical pathosis, factors influencing biofilm formation, mechanisms of their antimicrobial resistance, models developed to create biofilms, observation techniques of endodontic biofilms, and the effects of root canal irrigants and medicaments as well as lasers on endodontic biofilms. The search was performed from 1982 to December 2010, and was limited to papers in English language. The keywords searched on Medline were "biofilms and endodontics," "biofilms and root canal irrigation," "biofilms and intra-canal medicament," and "biofilms and lasers." The reference section of each article was manually searched to find other suitable sources of information.

  13. The composition and compression of biofilms developed on ultrafiltration membranes determine hydraulic biofilm resistance.

    Science.gov (United States)

    Derlon, Nicolas; Grütter, Alexander; Brandenberger, Fabienne; Sutter, Anja; Kuhlicke, Ute; Neu, Thomas R; Morgenroth, Eberhard

    2016-10-01

    This study aimed at identifying how to improve the level of permeate flux stabilisation during gravity-driven membrane filtration without control of biofilm formation. The focus was therefore on understanding (i) how the different fractions of the biofilms (inorganics particles, bacterial cells, EPS matrix) influence its hydraulic resistance and (ii) how the compression of biofilms impacts its hydraulic resistance, i.e., can water head be increased to increase the level of permeate flux stabilisation. Biofilms were developed on ultrafiltration membranes at 88 and 284 cm water heads with dead-end filtration for around 50 days. A larger water head resulted in a smaller biofilm permeability (150 and 50 L m(-2) h(-1) bar(-1) for biofilms grown at 88 cm and 284 cm water head, respectively). Biofilms were mainly composed of EPS (>90% in volume). The comparison of the hydraulic resistances of biofilms to model fouling layers indicated that most of the hydraulic resistance is due to the EPS matrix. The compressibility of the biofilm was also evaluated by subjecting the biofilms to short-term (few minutes) and long-term variations of transmembrane pressures (TMP). A sudden change of TMP resulted in an instantaneous and reversible change of biofilm hydraulic resistance. A long-term change of TMP induced a slow change in the biofilm hydraulic resistance. Our results demonstrate that the response of biofilms to a TMP change has two components: an immediate variation of resistance (due to compression/relaxation) and a long-term response (linked to biofilm adaptation/growth). Our results provide relevant information about the relationship between the operating conditions in terms of TMP, the biofilm structure and composition and the resulting biofilm hydraulic resistance. These findings have practical implications for a broad range of membrane systems. PMID:27318448

  14. The composition and compression of biofilms developed on ultrafiltration membranes determine hydraulic biofilm resistance.

    Science.gov (United States)

    Derlon, Nicolas; Grütter, Alexander; Brandenberger, Fabienne; Sutter, Anja; Kuhlicke, Ute; Neu, Thomas R; Morgenroth, Eberhard

    2016-10-01

    This study aimed at identifying how to improve the level of permeate flux stabilisation during gravity-driven membrane filtration without control of biofilm formation. The focus was therefore on understanding (i) how the different fractions of the biofilms (inorganics particles, bacterial cells, EPS matrix) influence its hydraulic resistance and (ii) how the compression of biofilms impacts its hydraulic resistance, i.e., can water head be increased to increase the level of permeate flux stabilisation. Biofilms were developed on ultrafiltration membranes at 88 and 284 cm water heads with dead-end filtration for around 50 days. A larger water head resulted in a smaller biofilm permeability (150 and 50 L m(-2) h(-1) bar(-1) for biofilms grown at 88 cm and 284 cm water head, respectively). Biofilms were mainly composed of EPS (>90% in volume). The comparison of the hydraulic resistances of biofilms to model fouling layers indicated that most of the hydraulic resistance is due to the EPS matrix. The compressibility of the biofilm was also evaluated by subjecting the biofilms to short-term (few minutes) and long-term variations of transmembrane pressures (TMP). A sudden change of TMP resulted in an instantaneous and reversible change of biofilm hydraulic resistance. A long-term change of TMP induced a slow change in the biofilm hydraulic resistance. Our results demonstrate that the response of biofilms to a TMP change has two components: an immediate variation of resistance (due to compression/relaxation) and a long-term response (linked to biofilm adaptation/growth). Our results provide relevant information about the relationship between the operating conditions in terms of TMP, the biofilm structure and composition and the resulting biofilm hydraulic resistance. These findings have practical implications for a broad range of membrane systems.

  15. Artificial biofilms establish the role of matrix interactions in staphylococcal biofilm assembly and disassembly

    OpenAIRE

    Stewart, Elizabeth J.; Mahesh Ganesan; Younger, John G.; Solomon, Michael J.

    2015-01-01

    We demonstrate that the microstructural and mechanical properties of bacterial biofilms can be created through colloidal self-assembly of cells and polymers, and thereby link the complex material properties of biofilms to well understood colloidal and polymeric behaviors. This finding is applied to soften and disassemble staphylococcal biofilms through pH changes. Bacterial biofilms are viscoelastic, structured communities of cells encapsulated in an extracellular polymeric substance (EPS) co...

  16. Game and player: C. albicans biofilm lifestyle and extracellular DNA

    OpenAIRE

    Martins, Margarida Isabel Barros Coelho; Uppuluri, Priya; Thomas, Derek P.; Cleary, Ian A.; Henriques, Mariana; Lopez-Ribot, José L.; Oliveira, Rosário

    2010-01-01

    DNA is as a structural component of bacterial biofilms extracellular matrix (ECM). Although evidences have shown that DNA may play a role in C. albicans biofilms, further studies are required to understand the contribution of extracellular DNA (eDNA) in C. albicans biofilm lifestyle. Herein we aimed to determine the eDNA content of C. albicans SC5314 biofilm ECM and the effect of DNase I and exogenous DNA treatments on biofilm formation and biofilm cells susceptibility to antifungals. First, ...

  17. Influence of flow on the structure of bacterial biofilms.

    OpenAIRE

    Stoodley, Paul; Boyle, John D.; Lappin-Scott, Hilary M.

    2000-01-01

    Bacteria attached to surfaces in biofilms are responsible for the contamination of industrial processes and many types of microbial infections and disease. Once established, biofilms are notoriously difficult to eradicate. A more complete understanding of how biofilms form and behave is crucial if we are to predict, and ultimately control, biofilm processes. A major breakthrough in biofilm research came in the early 1990’s when confocal scanning laser microscopy (CSLM) showed that biofilms fo...

  18. Current understanding of multi-species biofilms

    DEFF Research Database (Denmark)

    Yang, Liang; Liu, Yang; Wu, Hong;

    2011-01-01

    Direct observation of a wide range of natural microorganisms has revealed the fact that the majority of microbes persist as surface-attached communities surrounded by matrix materials, called biofilms. Biofilms can be formed by a single bacterial strain. However, most natural biofilms are actually...... formed by multiple bacterial species. Conventional methods for bacterial cleaning, such as applications of antibiotics and/or disinfectants are often ineffective for biofilm populations due to their special physiology and physical matrix barrier. It has been estimated that billions of dollars are spent...... every year worldwide to deal with damage to equipment, contaminations of products, energy losses, and infections in human beings resulted from microbial biofilms. Microorganisms compete, cooperate, and communicate with each other in multi-species biofilms. Understanding the mechanisms of multi...

  19. Mucosal biofilm detection in chronic otitis media

    DEFF Research Database (Denmark)

    Wessman, Marcus; Bjarnsholt, Thomas; Eickhardt-Sørensen, Steffen Robert;

    2015-01-01

    The objectives of this study were to examine middle ear biopsies from Greenlandic patients with chronic otitis media (COM) for the presence of mucosal biofilms and the bacteria within the biofilms. Thirty-five middle ear biopsies were obtained from 32 Greenlandic COM patients admitted to ear...... of the patients served as controls. PNA-FISH showed morphological signs of biofilms in 15 out of 35 (43 %) middle ear biopsies. In the control skin biopsies, there were signs of biofilms in eight out of 23 biopsies (30 %), probably representing skin flora. PCR and 16s sequencing detected bacteria in seven out...... of 20 (35 %) usable middle ear biopsies, and in two out of ten (20 %) usable control samples. There was no association between biofilm findings and PCR and 16s sequencing. Staphylococci were the most common bacteria in bacterial culture. We found evidence of bacterial biofilms in 43 % of middle ear...

  20. Innovative Strategies to Overcome Biofilm Resistance

    Directory of Open Access Journals (Sweden)

    Aleksandra Taraszkiewicz

    2013-01-01

    Full Text Available We review the recent literature concerning the efficiency of antimicrobial photodynamic inactivation toward various microbial species in planktonic and biofilm cultures. The review is mainly focused on biofilm-growing microrganisms because this form of growth poses a threat to chronically infected or immunocompromised patients and is difficult to eradicate from medical devices. We discuss the biofilm formation process and mechanisms of its increased resistance to various antimicrobials. We present, based on data in the literature, strategies for overcoming the problem of biofilm resistance. Factors that have potential for use in increasing the efficiency of the killing of biofilm-forming bacteria include plant extracts, enzymes that disturb the biofilm structure, and other nonenzymatic molecules. We propose combining antimicrobial photodynamic therapy with various antimicrobial and antibiofilm approaches to obtain a synergistic effect to permit efficient microbial growth control at low photosensitizer doses.

  1. Material modeling of biofilm mechanical properties.

    Science.gov (United States)

    Laspidou, C S; Spyrou, L A; Aravas, N; Rittmann, B E

    2014-05-01

    A biofilm material model and a procedure for numerical integration are developed in this article. They enable calculation of a composite Young's modulus that varies in the biofilm and evolves with deformation. The biofilm-material model makes it possible to introduce a modeling example, produced by the Unified Multi-Component Cellular Automaton model, into the general-purpose finite-element code ABAQUS. Compressive, tensile, and shear loads are imposed, and the way the biofilm mechanical properties evolve is assessed. Results show that the local values of Young's modulus increase under compressive loading, since compression results in the voids "closing," thus making the material stiffer. For the opposite reason, biofilm stiffness decreases when tensile loads are imposed. Furthermore, the biofilm is more compliant in shear than in compression or tension due to the how the elastic shear modulus relates to Young's modulus. PMID:24560820

  2. Development of a simplified biofilm model

    Science.gov (United States)

    Sarkar, Sushovan; Mazumder, Debabrata

    2015-11-01

    A simplified approach for analyzing the biofilm process in deriving an easy model has been presented. This simplified biofilm model formulated correlations between substrate concentration in the influent/effluent and at biofilm-liquid interface along with substrate flux and biofilm thickness. The model essentially considered the external mass transport according to Fick's Law, steady state substrate as well as biomass balance for attached growth microorganisms. In substrate utilization, Monod growth kinetics has been followed incorporating relevant boundary conditions at the liquid-biofilm interface and at the attachment surface. The numerical solution of equations was accomplished using Runge-Kutta method and accordingly an integrated computer program was developed. The model has been successfully applied in a distinct set of trials with varying range of representative input variables. The model performance was compared with available existing methods and it was found an easy, accurate method that can be used for process design of biofilm reactor.

  3. Artificial biofilms establish the role of matrix interactions in staphylococcal biofilm assembly and disassembly.

    Science.gov (United States)

    Stewart, Elizabeth J; Ganesan, Mahesh; Younger, John G; Solomon, Michael J

    2015-08-14

    We demonstrate that the microstructural and mechanical properties of bacterial biofilms can be created through colloidal self-assembly of cells and polymers, and thereby link the complex material properties of biofilms to well understood colloidal and polymeric behaviors. This finding is applied to soften and disassemble staphylococcal biofilms through pH changes. Bacterial biofilms are viscoelastic, structured communities of cells encapsulated in an extracellular polymeric substance (EPS) comprised of polysaccharides, proteins, and DNA. Although the identity and abundance of EPS macromolecules are known, how these matrix materials interact with themselves and bacterial cells to generate biofilm morphology and mechanics is not understood. Here, we find that the colloidal self-assembly of Staphylococcus epidermidis RP62A cells and polysaccharides into viscoelastic biofilms is driven by thermodynamic phase instability of EPS. pH conditions that induce phase instability of chitosan produce artificial S. epidermidis biofilms whose mechanics match natural S. epidermidis biofilms. Furthermore, pH-induced solubilization of the matrix triggers disassembly in both artificial and natural S. epidermidis biofilms. This pH-induced disassembly occurs in biofilms formed by five additional staphylococcal strains, including three clinical isolates. Our findings suggest that colloidal self-assembly of cells and matrix polymers produces biofilm viscoelasticity and that biofilm control strategies can exploit this mechanism.

  4. L-Tryptophan prevents Escherichia coli biofilm formation and triggers biofilm degradation.

    Science.gov (United States)

    Shimazaki, Junji; Furukawa, Soichi; Ogihara, Hirokazu; Morinaga, Yasushi

    2012-03-23

    The effect of deletion of trp operon and tna operon on the Escherichia coli biofilm formation was investigated in order to elucidate the role of L-tryptophan metabolism in biofilm formation. trp operon deletion mutants ΔtrpC, ΔtrpD and ΔtrpE deficient in L-tryptophan biosynthesis showed higher biofilm formation. In addition, ΔtnaC with increased L-tryptophan degradation activity showed higher biofilm formation. On the contrary, ΔtnaA deletion mutant which lost L-tryptophan degradation activity showed low biofilm formation. From these results, it was suggested that decrease of intracellular L-tryptophan level induced biofilm formation and increase of L-tryptophan repressed biofilm formation. So the effect of the addition of L-tryptophan to the medium on the E. coli biofilm formation was investigated. L-Tryptophan addition at starting culture decreased biofilm formation and furthermore L-tryptophan addition after 16 h culture induced the degradation of preformed biofilm. From the above results, it was suggested that maintenance of high intracellular L-tryptophan concentration prevents E. coli biofilm formation and elevation of intracellular L-tryptophan concentration triggers degradation of matured biofilm. PMID:22386992

  5. Antibiotic tolerance and resistance in biofilms

    DEFF Research Database (Denmark)

    Ciofu, Oana; Tolker-Nielsen, Tim

    2010-01-01

    One of the most important features of microbial biofilms is their tolerance to antimicrobial agents and components of the host immune system. The difficulty of treating biofilm infections with antibiotics is a major clinical problem. Although antibiotics may decrease the number of bacteria...... in biofilms, they will not completely eradicate the bacteria in vivo which may have important clinical consequences in form of relapses of the infection....

  6. Polymicrobial biofilms by diabetic foot clinical isolates.

    Science.gov (United States)

    Mottola, Carla; Mendes, João J; Cristino, José Melo; Cavaco-Silva, Patrícia; Tavares, Luís; Oliveira, Manuela

    2016-01-01

    Diabetes mellitus is a major chronic disease that continues to increase significantly. One of the most important and costly complications of diabetes is foot ulceration that may be colonized by pathogenic and antimicrobial resistant bacteria, which may express several virulence factors that could impair treatment success. These bacterial communities can be organized in polymicrobial biofilms, which may be responsible for diabetic foot ulcer (DFU) chronicity. We evaluated the influence of polymicrobial communities in the ability of DFU isolates to produce biofilm, using a microtiter plate assay and a multiplex fluorescent in situ hybridization, at three time points (24, 48, 72 h), after evaluating biofilm formation by 95 DFU isolates belonging to several bacterial genera (Staphylococcus, Corynebacterium, Enterococcus, Pseudomonas and Acinetobacter). All isolates were biofilm-positive at 24 h, and the amount of biofilm produced increased with incubation time. Pseudomonas presented the higher biofilm production, followed by Corynebacterium, Acinetobacter, Staphylococcus and Enterococcus. Significant differences were found in biofilm formation between the three time points. Polymicrobial communities produced higher biofilm values than individual species. Pseudomonas + Enterococcus, Acinetobacter + Staphylococcus and Corynebacterium + Staphylococcus produced higher biofilm than the ones formed by E. faecalis + Staphylococcus and E. faecalis + Corynebacterium. Synergy between bacteria present in dual or multispecies biofilms has been described, and this work represents the first report on time course of biofilm formation by polymicrobial communities from DFUs including several species. The biological behavior of different bacterial species in polymicrobial biofilms has important clinical implications for the successful treatment of these infections.

  7. Penetration of erythromycin through Staphylococcus epidermidis biofilm

    Institute of Scientific and Technical Information of China (English)

    LIN Mao-hu; HE Lei; GAO Jie; LIU Yun-xi; SUO Ji-jiang; XING Yu-bin; JIA Ning

    2013-01-01

    Background The catheter related infection caused by Staphylococcus epiderrnidis biofilm is increasing and difficult to treat by antimicrobial chemotherapy.The properties of biofilms that give rise to antibiotic resistance are only partially understood.This study aimed to elucidate the penetration of erythromycin through Staphylococcus epidermidis biofilm.Methods The penetration ratio of erythromycin through Staphylococcus epidermidis biofilms of 1457,1457-msrA,and wild isolate S68 was detected by biofilm penetration model at different time points according to the standard regression curve.The RNNDNA ratio and the cell density within the biofilms were observed by confocal laser microscope and transmission electromicroscope,respectively.Results The penetration ratios of erythromycin through the biofilms of 1457,1457-msrA,and S68 after cultivation for 36 hours were 0.93,0.55 and 0.4,respectively.The erythromycin penetration ratio through 1457 biofilm (0.58 after 8 hours)was higher than that through the other two (0.499 and 0.31 after 24 hours).Lower growth rate of the cells in biofilm was shown,with reduction of RNA/DNA proportion observed by confocal laser microscope through acridine orange stain.Compared with the control group observed by transmission electrmicroscope,the cell density of biofilm air face was lower than that of agar face,with more cell debris.Conclusions Erythromycin could penetrate to the Staphylococcus epidermidis biofilm,but could not kill the cells thoroughly.The lower growth rate of the cells within biofilm could help decreasing the erythromycin susceptibility.

  8. Water quality and Health: Biofilms and Legionella

    OpenAIRE

    Gea-Izquierdo Enrique; Loza-Murguía Manuel

    2016-01-01

    This paper discusses the drinking water quality and its relation to Public Health. It introduces the concept of biofilm formation under stood from the perspective of biological contamination. In particular, attends to Legionella spp., ecological niches and related legionnaires’ disease. It also develops the evolution of biofilms, their influence on water quality, treatment and control. Finally, shows the relationship between certain microorganisms included in aquatic biofilms, the substrate w...

  9. Drug resistance mechanisms of fungal biofilms

    OpenAIRE

    Seneviratne, CJ; Samaranayake, LP

    2011-01-01

    Fungi are ubiquitous in nature and exist in soil, water, plants, and in animals and humans. Similar to bacteria, fungi also form confluent biofilms either singly (mono-species) or with other microbial species (mixed-species). Fungal biofilms are known to be highly resistant to the adverse environmental conditions including antimicrobials and biocide compared to its planktonic (free-floating) counterparts. Although bacterial biofilms have been studied in detail, relatively little is known of f...

  10. Targeting quorum sensing in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Jakobsen, Tim Holm; Bjarnsholt, Thomas; Jensen, Peter Østrup;

    2013-01-01

    Bacterial resistance to conventional antibiotics combined with an increasing acknowledgement of the role of biofilms in chronic infections has led to a growing interest in new antimicrobial strategies that target the biofilm mode of growth. In the aggregated biofilm mode, cell-to-cell communication...... alternative antibacterial strategies. Here, we review state of the art research of quorum sensing inhibitors against the opportunistic human pathogen Pseudomonas aeruginosa, which is found in a number of biofilm-associated infections and identified as the predominant organism infecting the lungs of cystic...

  11. Aspartate inhibits Staphylococcus aureus biofilm formation.

    Science.gov (United States)

    Yang, Hang; Wang, Mengyue; Yu, Junping; Wei, Hongping

    2015-04-01

    Biofilm formation renders Staphylococcus aureus highly resistant to conventional antibiotics and host defenses. Four D-amino acids (D-Leu, D-Met, D-Trp and D-Tyr) have been reported to be able to inhibit biofilm formation and disassemble established S. aureus biofilms. We report here for the first time that both D- and L-isoforms of aspartate (Asp) inhibited S. aureus biofilm formation on tissue culture plates. Similar biofilm inhibition effects were also observed against other staphylococcal strains, including S. saprophyticus, S. equorum, S. chromogenes and S. haemolyticus. It was found that Asp at high concentrations (>10 mM) inhibited the growth of planktonic N315 cells, but at subinhibitory concentrations decreased the cellular metabolic activity without influencing cell growth. The decreased cellular metabolic activity might be the reason for the production of less protein and DNA in the matrix of the biofilms formed in the presence of Asp. However, varied inhibition efficacies of Asp were observed for biofilms formed by clinical staphylococcal isolates. There might be mechanisms other than decreasing the metabolic activity, e.g. the biofilm phenotypes, affecting biofilm formation in the presence of Asp.

  12. Aspartate inhibits Staphylococcus aureus biofilm formation.

    Science.gov (United States)

    Yang, Hang; Wang, Mengyue; Yu, Junping; Wei, Hongping

    2015-04-01

    Biofilm formation renders Staphylococcus aureus highly resistant to conventional antibiotics and host defenses. Four D-amino acids (D-Leu, D-Met, D-Trp and D-Tyr) have been reported to be able to inhibit biofilm formation and disassemble established S. aureus biofilms. We report here for the first time that both D- and L-isoforms of aspartate (Asp) inhibited S. aureus biofilm formation on tissue culture plates. Similar biofilm inhibition effects were also observed against other staphylococcal strains, including S. saprophyticus, S. equorum, S. chromogenes and S. haemolyticus. It was found that Asp at high concentrations (>10 mM) inhibited the growth of planktonic N315 cells, but at subinhibitory concentrations decreased the cellular metabolic activity without influencing cell growth. The decreased cellular metabolic activity might be the reason for the production of less protein and DNA in the matrix of the biofilms formed in the presence of Asp. However, varied inhibition efficacies of Asp were observed for biofilms formed by clinical staphylococcal isolates. There might be mechanisms other than decreasing the metabolic activity, e.g. the biofilm phenotypes, affecting biofilm formation in the presence of Asp. PMID:25687923

  13. Spatial structure, cooperation and competition in biofilms.

    Science.gov (United States)

    Nadell, Carey D; Drescher, Knut; Foster, Kevin R

    2016-09-01

    Bacteria often live within matrix-embedded communities, termed biofilms, which are now understood to be a major mode of microbial life. The study of biofilms has revealed their vast complexity both in terms of resident species composition and phenotypic diversity. Despite this complexity, theoretical and experimental work in the past decade has identified common principles for understanding microbial biofilms. In this Review, we discuss how the spatial arrangement of genotypes within a community influences the cooperative and competitive cell-cell interactions that define biofilm form and function. Furthermore, we argue that a perspective rooted in ecology and evolution is fundamental to progress in microbiology. PMID:27452230

  14. Electroactive biofilms of sulphate reducing bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cordas, Cristina M.; Guerra, L. Tiago; Xavier, Catarina [Requimte-CQFB, Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Moura, Jose J.G. [Requimte-CQFB, Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)], E-mail: jose.moura@dq.fct.unl.pt

    2008-12-01

    Biofilms formed from a pure strain of Desulfovibrio desulfuricans 27774 on stainless steel and graphite polarised surfaces were studied. The polarisation conditions applied were -0.4 V vs. SCE for different times. A cathodic current related with the biofilms growth was observed with a maximum intensity of -270 mA m{sup -2} that remained stable for several days using graphite electrodes. These sulphate reducing bacteria biofilms present electrocatalytic activity towards hydrogen and oxygen reduction reactions. Electrode polarisation has a selective effect on the catalytic activity. The biofilms were also observed by scanning electronic microscopy revealing the formation of homogeneous films on the surfaces.

  15. Biofilm responses to marine fish farm wastes

    Energy Technology Data Exchange (ETDEWEB)

    Sanz-Lazaro, Carlos, E-mail: carsanz@um.es [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100 Murcia (Spain); Navarrete-Mier, Francisco; Marin, Arnaldo [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100 Murcia (Spain)

    2011-03-15

    The changes in the biofilm community due to organic matter enrichment, eutrophication and metal contamination derived from fish farming were studied. The biofilm biomass, polysaccharide content, trophic niche and element accumulation were quantified along an environmental gradient of fish farm wastes in two seasons. Biofilm structure and trophic diversity was influenced by seasonality as well as by the fish farm waste load. Fish farming enhanced the accumulation of organic carbon, nutrients, selenium and metals by the biofilm community. The accumulation pattern of these elements was similar regardless of the structure and trophic niche of the community. This suggests that the biofilm communities can be considered a reliable tool for assessing dissolved aquaculture wastes. Due to the ubiquity of biofilms and its wide range of consumers, its role as a sink of dissolved wastes may have important implications for the transfer of aquaculture wastes to higher trophic levels in coastal systems. - Research highlights: > Biofilms can act as a trophic pathway of fish farm dissolved wastes. > Biofilms are reliable tools for monitoring fish farm dissolved wastes. > The influence of the fish farm dissolved wastes can be detected 120-350 m from farm. - Under the influence of fish farming biofilm accumulates organic carbon, nutrients, selenium and metals, regardless of the structure and trophic niche of the community.

  16. Antimicrobial and biofilm inhibiting diketopiperazines.

    Science.gov (United States)

    de Carvalho, M P; Abraham, W-R

    2012-01-01

    Diketopiperazines are the smallest cyclic peptides known. 90% of Gram-negative bacteria produce diketopiperazines and they have also been isolated from Gram-positive bacteria, fungi and higher organisms. Biosynthesis of cyclodipeptides can be achieved by dedicated nonribosomal peptide synthetases or by a novel type of synthetases named cyclopeptide synthases. Since the first report in 1924 a large number of bioactive diketopiperazines was discovered spanning activities as antitumor, antiviral, antifungal, antibacterial, antiprion, antihyperglycemic or glycosidase inhibitor agents. As infections are of increasing concern for human health and resistances against existing antibiotics are growing this review focuses on the antimicrobial activities of diketopiperazines. The antibiotic bicyclomycin is a diketopiperazine and structure activity studies revealed the unique nature of this compound which was finally developed for clinical applications. The antimicrobial activities of a number of other diketopiperazines along with structure activity relationships are discussed. Here a special focus is on the activity-toxicity problem of many compounds setting tight limitations to their application as drugs. Not only these classical antimicrobial activities but also proposed action in modulating bacterial communication as a new target to control biofilms will be evaluated. Pathogens organized in biofilms are difficult to eradicate because of the increase of their tolerance for antibiotics for several orders. Diketopiperazines were reported to modulate LuxR-mediated quorum-sensing systems of bacteria, and they are considered to influence cell-cell signaling offering alternative ways of biofilm control by interfering with microbial communication. Concluding the review we will finally discuss the potential of diketopiperazines in the clinic to erase biofilm infections.

  17. Supermarket refrigerators with natural refrigerants; Supermarktkaelteanlagen mit natuerlichen Kaeltemitteln. Erfahrungsbericht

    Energy Technology Data Exchange (ETDEWEB)

    Haaf, S.; Heinbokel, B. [Linde AG, Koeln (Germany). Gechaeftsbereich Linde Kaeltetechnik

    2002-09-01

    In view of the high contribution to global warming of H-CFC refrigerants, substitution has been a key concern for several years now. Leakage protection measures were enhanced, and Linde also installed many supermarket refrigerators with natural refrigerants, i.e. ammonia, propene and carbon dioxide. The environmental and economic aspects are assessed on the basis of the experience gained, and the systems are compared with H-CFC refrigeration systems. [German] Wegen des betraechtlichen Treibhauspotentials von HFKW-Kaeltemitteln werden seit Jahren Anstrengungen unternommen, um den von diesen Stoffen ausgehenden Treibhauseffekt zu reduzieren. Neben Massnahmen zur Verminderung von Leckagen sowie zur Verringerung von Kaeltemittel-Fuellmengen wurden im Laufe der letzten 10 Jahre von Linde auch zahlreiche Kaelteanlagen mit den natuerlichen Kaeltemitteln Ammoniak, Propen und Kohlendioxid in Supermaerkten installiert. Auf Basis der gesammelten Erfahrungen wird eine Einschaetzung der umweltspezifischen und wirtschaftlichen Aspekte im Vergleich zu Anlagen mit HFKW-Kaeltemitteln vorgenommen. (orig.)

  18. The MIT / NASA Langley Magnetic Suspension/Balance System

    Science.gov (United States)

    1991-01-01

    A shuttle model is magnetically suspended in the transparent octagonal test section of the MIT / NASA Langley 6 Inch MSBS. Massive power supplies are required to drive electromagnets for model position control. A unique electromagnetic position sensor, similar to a linear variable differential transformer, provides five degrees of freedom for the test model. The low speed (Mach 0.5) wind tunnel was hand crafted from mahogany. Aerodynamic forces on the test model are measured by the proportional electrical current used to hold the model in place. The system was built by MIT in the late sixties and was relocated to Langley in the mid eighties. In a joint effort with Old Dominion University in 1992 the MSBS was used to test the aerodynamics of store separation, simulating a bomb released from an aircraft. The system has been donated to Old Dominion University.

  19. Properties of hybrid stars in an extended MIT bag model

    Institute of Scientific and Technical Information of China (English)

    BAO Tmurbagan; LIU Guang-Zhou; ZHU Ming-Feng

    2009-01-01

    The properties of hybrid stars are investigated in the framework of the relativistic mean field theory (RMFT) and an MIT bag model with density-dependent bag constant to describe the hadron phase (HP) and quark phase (QP), respectively. We find that the density-dependent B(p) decreases with baryon density p; this decrement makes the strange quark matter become more energetically favorable than ever, which makes the threshold densities of the hadron-quark phase transition lower than those of the original bag constant case. In this case, the hyperon degrees of freedom can not be considered. As a result, the equations of state of a star in the mixed phase (MP) become softer whereas those in the QP become stiffer, and the radii of the star obviously decrease. This indicates that the extended MIT bag model is more suitable to describe hybrid stars with small radii.

  20. MIT LMFBR blanket research project. Final summary report

    Energy Technology Data Exchange (ETDEWEB)

    Driscoll, M.J.

    1983-08-01

    This is a final summary report on an experimental and analytical program for the investigation of LMFBR blanket characteristics carried out at MIT in the period 1969 to 1983. During this span of time, work was carried out on a wide range of subtasks, ranging from neutronic and photonic measurements in mockups of blankets using the Blanket Test Facility at the MIT Research Reactor, to analytic/numerical investigations of blanket design and economics. The main function of this report is to serve as a resource document which will permit ready reference to the more detailed topical reports and theses issued over the years on the various aspects of project activities. In addition, one aspect of work completed during the final year of the project, on doubly-heterogeneous blanket configurations, is documented for the record.

  1. MIT LMFBR blanket research project. Final summary report

    International Nuclear Information System (INIS)

    This is a final summary report on an experimental and analytical program for the investigation of LMFBR blanket characteristics carried out at MIT in the period 1969 to 1983. During this span of time, work was carried out on a wide range of subtasks, ranging from neutronic and photonic measurements in mockups of blankets using the Blanket Test Facility at the MIT Research Reactor, to analytic/numerical investigations of blanket design and economics. The main function of this report is to serve as a resource document which will permit ready reference to the more detailed topical reports and theses issued over the years on the various aspects of project activities. In addition, one aspect of work completed during the final year of the project, on doubly-heterogeneous blanket configurations, is documented for the record

  2. Typenbildung mit quantitativen und qualitativen Daten : methodologische Überlegungen

    OpenAIRE

    Promberger, Markus (Hrsg.)

    2011-01-01

    In diesem Essay wird gezeigt, dass die Verschränkung von qualitativen und quantitativen Methoden im Forschungsprozess nicht nur durch das Zählen von Wörtern in qualitativen Dokumenten, durch Exemplifikation von Statistiken mit Einzelfallstudien, durch 'hypothesengenerierende' Explorationsstudien oder ähnliches geschehen kann. Vielmehr stellt die Typenbildung einen Schlüsselschritt für die Genese konvergenter Befunde aus beiden methodischen Richtungen dar. Der Aufsatz skizziert eine wissenscha...

  3. Staatlicher Umgang mit sexuellem Mißbrauch

    OpenAIRE

    Oberloskamp, Helga

    1996-01-01

    Das Thema bedarf differenzierter Betrachtung, da sich "der Staat" in seinen drei Gewalten Legislative, Exekutive, Judikative darstellt. Die Exekutive wird vor allem durch das Jugendamt repräsentiert, dessen Aufgaben das KJHG differenziert benennt. Dagegen sagt das Gesetz wenig darüber aus, wie die Aufgaben zu erledigen sind. Allerdings ist eine Kooperation mit Freien Trägern der Jugendhilfe, dem Vormundschafts- und Familiengericht und anderen bezeichneten Stellen (z B Schule, Polizei) vorgesc...

  4. Modellierung und Verifikation von Eisenbahn-Infrastrukturen mit semantischen Technologien

    OpenAIRE

    Lodemann, Michael

    2014-01-01

    Diese Arbeit zeigt, wie semantische Technologien (Sprachen und Werkzeuge) genutzt werden können, um Eisenbahn-Infrastrukturen zu modellieren und zu verifizieren. Dazu wurde ein semantisches Domänen-Modell entworfen und implementiert, das sowohl die Elemente von Eisenbahn-Infrastrukturen und deren Eigenschaften als auch die Beziehungen dieser Elemente untereinander darstellen kann. Zur Modellierung wurde die Web Ontology Language (OWL) in Kombination mit der Semantic Web Rule Language (SWRL) v...

  5. Herstellung dotierter Nanodiamantpartikel und ihre Funktionalisierung mit schwefelhaltigen Gruppen

    OpenAIRE

    Heyer, Steffen

    2015-01-01

    In dieser Dissertation werden Methoden zur Darstellung von Stickstoff- und Bor-dotierten Nanodiamantpartikeln durch Vermahlung von makroskopischem HPHT- und CVD-Diamant mit unterschiedlichen Mühlen und Mahlverfahren beschrieben. Untersucht wird dabei der Zusammenhang von erzielten Teilchengrößen nach dem Mahlen und den Kristallitgrößen der Ausgangsdiamanten sowie der angewandten Mahlmethode. Durch Anwendung verschiedener oxidativer Methoden wird während des Mahlens entstehender sp2-Kohlenstof...

  6. Hochtemperaturverhalten von Stahlbetonplatten mit Textilbetonverstärkung

    OpenAIRE

    Hothan, Sascha; Ehlig, Daniel

    2011-01-01

    Die Verwendung von Endlosfilamenten aus Carbon als Bewehrungsmaterial für Beton, sogenannter Textilbeton, bietet die Möglichkeit der Sanierung und der Verstärkung bestehender Stahlbetonkonstruktionen. Dabei muss die Frage nach dem Feuerwiderstand von derart verstärkten Tragwerken beantwortet werden. Aufschluss darüber liefern Brandversuche. Mit Textilbeton verstärkte Stahlbetonplatten haben in Brandversuchen nach der Einheits- Temperaturzeitkurve bei 33 % der Traglast mehr als 60 Minuten stan...

  7. Aktivierung von Makrophagen durch Maillard-Produkte mit Aminoreduktonstruktur

    OpenAIRE

    Wühr, Andrea

    2010-01-01

    Durch Zubereitung oder Lagerung von Lebensmitteln, aber auch in vivo reagieren in der Maillard-Reaktion reduzierende Zucker mit Aminen, Aminosäuren oder Proteinen zu einer komplexen Mischung an Maillard-Produkten. Noch ungeklärt ist bislang in wie weit sich der Verzehr dieser Produkte positiv oder negativ auf die Gesundheit des Menschen auswirkt. Aufgrund vieler erwünschter sensorischer Eigenschaften dieser Produkte (braune Farbe, Geschmack und Aroma), werden bedeutende Mengen durch die Nahru...

  8. Funktionsdiagnostik von Inselzellen des Schweins mit einer miniaturisierten Mikroperifusionskammer

    OpenAIRE

    Schlosser, Stefan

    2007-01-01

    Die Forschung um die Optimierung der Insel-Transplantation nimmt in der Behandlung des Typ I Diabetes eine Vorreiterstellung ein. Nachdem im Zeitraum von drei Jahrzehnten Fortschritte im Bereich der Insel-Isolierung und Immunosuppression gemacht wurden, stehen wir heute am Beginn des klinischen Einsatzes dieser Technik an ausgewählten Patientengruppen. Ziel der vorliegenden Arbeit ist die umfassende Funktionsdiagnostik isolierter porziner mikroverkapselter Inseln. Mit Hilfe einer miniaturisie...

  9. Internationales Team Building aus britischer Perspektive: mit Schwerpunkt interkultureller Kompetenz

    OpenAIRE

    Bründl-Price, Sonja

    2004-01-01

    In Zeiten wachsender Globalisierung sind internationale Teams alltäglich und werden mit allen möglichen Schattierungen von Erfolg und Misserfolg konfrontiert. Menschen unterschiedlichen kulturellen Hintergrundes bemühen sich, einander zu verstehen, interkulturelle Hindernisse zu überwinden und Gruppenpotenziale zu optimieren. Oft erübrigt sich die Frage nach der Erfolgsrate internationaler Teams im Vergleich zu monokulturellen Gruppen, da Internationalität heutzutage wesentlicher Bestandteil ...

  10. MitBASE: a comprehensive and integrated mitochondrial DNA database

    OpenAIRE

    Antimonelli, M.; Altamura, N.; Benne, R.; Boyen, C; Brennicke, A; Carone, A; Cooper, J. M.; D'Elia, D.; Montalvo, de, A.; Pinto, de, B.; Robertis, De, M.; Golik, P.; Grienenberger, J M; Knoop, V.; Lanave, C.

    1999-01-01

    MitBASE is an integrated and comprehensive database of mitochondrial DNA data which collects all available information from different organisms and from intraspecie variants and mutants. Research institutions from different countries are involved, each in charge of developing, collecting and annotating data for the organisms they are specialised in. The design of the actual structure of the database and its implementation in a user-friendly format are the care of the European Bioinformatics I...

  11. Gruppendiskussionen mit Kindern : die dokumentarische Interpretation von Spielpraxis und Diskursorganisation

    OpenAIRE

    Nentwig-Gesemann, Iris

    2002-01-01

    "Im Interaktionsgeflecht der Gleichaltrigenkultur produzieren Kinder als soziale Akteure soziale Wirklichkeit und kulturelle Bedeutungen. Gruppendiskussionen und die dokumentarische Methode der Interpretation werden als geeignete Verfahren vorgestellt, mit denen im Rahmen der Kindheitsforschung neue Zugänge zur Perspektive der Kinder und ihren alltagskulturellen Praktiken eröffnet werden können. Über die Reflexion und Rekonstruktion forschungspraktischer Erfahrungen wird hier die schrittweise...

  12. Experimentelle und simulative Tropfenaufprallbestimmung mit einem piezoelektrischen Sensor

    OpenAIRE

    Bulur, Ertan; Mendig, Christian

    2015-01-01

    Im Rahmen des SuLaDi Projekts wird unter anderem an Eiserkennungskonzepten gearbeitet. Damit sich überhaupt ein Eisansatz bilden kann, muss auf der entsprechenden Fläche des Versuchskörpers Wasser vorhanden sein. Wasser gelangt unter realen Bedingungen, wie auch im Windkanalversuch tropfenweise auf den Versuchskörper und gefriert. Diese Arbeit beschäftigt sich mit der Problemstellung, ob der Aufprall eines Wassertropfens durch den Einsatz einer Piezofolie aus Polyvinylidenfluorid erkannt w...

  13. Formgedächtnis-Mikroventile mit hoher Energiedichte.

    OpenAIRE

    Liu, Yong; Kohl, Manfred

    2007-01-01

    Diese Arbeit beschreibt die Entwicklung von Formgedächtnis-Mikroventilen und daraus aufgebauter Durchflussregler für mikrofluidische Anwendungen. Ein erklärtes Ziel war die Bereitstellung einer hohen Energiedichte, um möglichst kompakte Bauelemente mit großem Arbeitsvermögen zu realisieren. Von den bekannten Energiewandlungsprinzipien zeigt der Formgedächtnis- (FG-) Effekt die höchste Energiedichte. Daher liegt der Schwerpunkt der Arbeit in der Entwicklung mikrosystemt...

  14. Vogelkundliche Fachliteratur und Internetquellen mit www.vifabio.de recherchieren

    OpenAIRE

    Dähne, Judith

    2010-01-01

    Die Virtuelle Fachbibliothek Biologie (www.vifabio.de) bündelt die Recherche nach wissenschaftlich hochwertigen Quellen aus Bibliotheken, Aufsatzbanken und Internet. Zentrales Element von vifabio ist dabei der Virtuelle Katalog: Mit einer Suchanfrage werden mehrere Kataloge zoologisch bzw. ornithologisch relevanter Bibliotheken, Zeitschriftendatenbanken wie Zoological Record (Nationallizenz 1864 bis 2007 für Nutzer in akademischen Einrichtungen), BioLIS und der Aufsatzkatalog OLC, sowie Lande...

  15. Resonanzionisations-Massenspektrometrie mit gepulsten und kontinuierlichen Lasern an Plutonium

    OpenAIRE

    Kunz, Peter

    2004-01-01

    Zusammenfassung Zur Weiterentwicklung derResonanzionisations-Massenspektrometrie (RIMS) für dieUltra-Spurenanalyse von Plutonium wurde im Rahmen dieserArbeit eine neue RIMS-Apparatur konzipiert und aufgebaut.Erstmals wurden bei der spektroskopischen Untersuchung vonPlutonium schmalbandige kontinuierliche Laser verwendet. Eswurdenumfangreiche Messreihen durchgeführt, um denResonanzionisationsprozess von Plutonium mit kontinuierlichenLasern zuspezifizieren und möglichst effiziente Anregungsl...

  16. Quark Orbital Angular Momentum in the MIT Bag Model

    OpenAIRE

    Burkardt, Matthias; Jarrah, Abdullah

    2010-01-01

    Using the MIT bag model, we study the contribution from the gluon vector potential due to the spectators to the orbital angular momentum of a quark in the bag model. For $\\alpha_s = {\\cal O}(1)$, this spectator contribution to the quark orbital angular momentum in the gauge-covariant Ji decomposition is of the same order as the non gauge-covariant quark orbital angular momentum and its magnitude is larger for $d$ than for $u$ quarks and negative for both.

  17. Hochauflösende Verarbeitung von Radardaten mit synthetischer Apertur

    OpenAIRE

    Mittermayer, Josef

    2000-01-01

    Diese Arbeit stellt das neuartige Frequenz-Skalierungs-Verfahren zur effizienten und genauen Verarbeitung von Spotlight-SAR-Daten ohne Interpolation vor. Es wird eine genaue Modellierung der Spotlight-Abbildungsgeometrie eingeführt. Eine neue analytische Formulierung für SAR-Rohdaten mit Dechirp on Receive-Operation wird abgeleitet. Aufbauend auf dieser Formulierung erfolgt die Entwicklung einer interpolationsfreien Korrektur der Zielentfernungsänderung, der sogenannten Frequenz-Skalierung. ...

  18. Leistungen an Familien mit Kindern im internationalen Vergleich

    OpenAIRE

    Clasen, Jochen

    1994-01-01

    'Ausgehend von einer Beschreibung von Zielsetzung und Methode werden wesentliche Ergebnisse einer empirisch vergleichenden Studie über familienpolitische Fördersysteme in den Mitgliedsländern der Europäischen Gemeinschaft, Norwegen, Australien und den USA vorgestellt. Im Zentrum des Projekts stehen die Darstellung der Struktur und die Bewertung von Maßnahmen, die Familien mit Kindern direkt und indirekt unterstützen ('child support packages'). Es wurde versucht, die monetären Entlastungseffek...

  19. CWSpace: Archiving MIT OpenCourseWare in DSpace

    OpenAIRE

    Reilly, William

    2005-01-01

    Charged with archiving all of MIT's OpenCourseWare content, the CWSpace project has been exploring new kinds of development on the Dspace platform in two key directions: packaging metadata and protocols. This talk reports on progress towards the support of new, standards-based ingest (and dissemination) functionality (e.g., IMS Content Packaging), as well as in the area of new "lightweight network interfaces" capabilities (e.g., Web Services protocols). Each of these development efforts is de...

  20. Mitä väliä on historialla?

    OpenAIRE

    Miettinen, Tiina; Toivo, Raisa (ed.) Maria

    2016-01-01

    Mitä väliä on historialla (“What good is history?”) is edited by Dr. Tiina Miettinen and Dr. Raisa Maria Toivo. Can history be useful and if so, what is it useful for? This book explores the impact of history and historical research. It gives a general introduction and various case studies – together with a piece of fiction – on how different parts of society can benefit, or have used, the study of history.

  1. Knochenablation mit fasergeführtem XeCl-Excimerlaserstrahl

    OpenAIRE

    Jahn, Renate; Dressel, Martin; Langendorff, Hans-Ulrich; Neu, Walter; Jungbluth, Karl-Heinz

    1991-01-01

    Eine neue Lasertechnik erweckt durch ihr "athermisches" Abtragungsprinzip nun auch das Interesse der Unfallchirurgen. Mit hoher Schnittqualität und präzisem Bohren bei industriellen Fertigungsverfahren zeigte der Excimerlaser andere Wege in der Oberflächenbearbeitung von Hartmaterialien (Glas, Keramik, Diamant) auf.Die Materialabtragung erfolgt nicht mehr durch ausschließlich photothermische Wirkung, sondern indem auch molekulare Bindungen aufgrund der hohen Photonenenergie des Lasers aufgebr...

  2. Protein-based biofilm matrices in Staphylococci

    Directory of Open Access Journals (Sweden)

    Pietro eSpeziale

    2014-12-01

    Full Text Available Staphylococcus aureus and Staphylococcus epidermidis are the most important etiological agents of biofilm associated-infections on indwelling medical devices. Biofilm infections may also develop independently of indwelling devices, e.g. in native valve endocarditis, bone tissue and open wounds. After attachment to tissue or indwelling medical devices that have been conditioned with host plasma proteins, staphylococcal biofilms grow and produce a specific environment which provides the conditions for cell-cell interaction and formation of multicellular communities. Bacteria living in biofilms express a variety of macromolecules, including exopolysaccharides, proteins, extracellular eDNA and other polymers. The S. aureus surface protein C and G (SasC and SasG, clumping factor B (ClfB, serine aspartate repeat protein (SdrC, the biofilm-associated protein (Bap and the fibronectin/fibrinogen-binding proteins (FnBPA and FnBPB are individually implicated in biofilm matrix formation. In S. epidermidis, a protein named accumulation-associated protein (Aap contributes to both the primary attachment phase and the establishment of intercellular connections by forming fibrils on the cell surface. In S. epidermidis proteinaceous biofilm formation can also be mediated by the extracellular matrix binding protein (Embp and S. epidermidis surface protein C (SesC. Additionally, multifunctional proteins such as extracellular adherence protein (Eap and extracellular matrix protein binding protein (Emp of S. aureus and the iron-regulated surface determinant protein C (IsdC of S. lugdunensis can promote biofilm formation in iron-depleted conditions. This multitude of proteins intervene at different stages of biofilm formation with certain proteins contributing to biofilm accumulation and others mediating primary attachment to surfaces. This review examines the contribution of proteins to biofilm formation in staphylococci. The potential to develop vaccines to prevent

  3. Oral biofilm models for mechanical plaque removal.

    Science.gov (United States)

    Verkaik, Martinus J; Busscher, Henk J; Rustema-Abbing, Minie; Slomp, Anje M; Abbas, Frank; van der Mei, Henny C

    2010-08-01

    In vitro plaque removal studies require biofilm models that resemble in vivo dental plaque. Here, we compare contact and non-contact removal of single and dual-species biofilms as well as of biofilms grown from human whole saliva in vitro using different biofilm models. Bacteria were adhered to a salivary pellicle for 2 h or grown after adhesion for 16 h, after which, their removal was evaluated. In a contact mode, no differences were observed between the manual, rotating, or sonic brushing; and removal was on average 39%, 84%, and 95% for Streptococcus mutans, Streptococcus oralis, and Actinomyces naeslundii, respectively, and 90% and 54% for the dual- and multi-species biofilms, respectively. However, in a non-contact mode, rotating and sonic brushes still removed considerable numbers of bacteria (24-40%), while the manual brush as a control (5-11%) did not. Single A. naeslundii and dual-species (A. naeslundii and S. oralis) biofilms were more difficult to remove after 16 h growth than after 2 h adhesion (on average, 62% and 93% for 16- and 2-h-old biofilms, respectively), while in contrast, biofilms grown from whole saliva were easier to remove (97% after 16 h and 54% after 2 h of growth). Considering the strong adhesion of dual-species biofilms and their easier more reproducible growth compared with biofilms grown from whole saliva, dual-species biofilms of A. naeslundii and S. oralis are suggested to be preferred for use in mechanical plaque removal studies in vitro. PMID:19565279

  4. Biofilms in chronic infections - a matter of opportunity - monospecies biofilms in multispecies infections

    DEFF Research Database (Denmark)

    Burmølle, Mette; Thomsen, Trine Rolighed; Fazli, Mustafa;

    2010-01-01

    It has become evident that aggregation or biofilm formation is an important survival mechanism for bacteria in almost any environment. In this review, we summarize recent visualizations of bacterial aggregates in several chronic infections (chronic otitis media, cystic fibrosis, infection due...... to permanent tissue fillers and chronic wounds) both as to distribution (such as where in the wound bed) and organization (monospecies or multispecies microcolonies). We correlate these biofilm observations to observations of commensal biofilms (dental and intestine) and biofilms in natural ecosystems (soil......). The observations of the chronic biofilm infections point toward a trend of low bacterial diversity and sovereign monospecies biofilm aggregates even though the infection in which they reside are multispecies. In contrast to this, commensal and natural biofilm aggregates contain multiple species that are believed...

  5. Alginate production affects Pseudomonas aeruginosa biofilm development and architecture, but is not essential for biofilm formation

    DEFF Research Database (Denmark)

    Stapper, A.P.; Narasimhan, G.; Oman, D.E.;

    2004-01-01

    Extracellular polymers can facilitate the non-specific attachment of bacteria to surfaces and hold together developing biofilms. This study was undertaken to qualitatively and quantitatively compare the architecture of biofilms produced by Pseudomonas aeruginosa strain PAO1 and its alginate......-overproducing (mucA22) and alginate-defective (algD) variants in order to discern the role of alginate in biofilm formation. These strains, PAO1, Alg(+) PAOmucA22 and Alg(-) PAOalgD, tagged with green fluorescent protein, were grown in a continuous flow cell system to characterize the developmental cycles...... of their biofilm formation using confocal laser scanning microscopy. Biofilm Image Processing (BIP) and Community Statistics (COMSTAT) software programs were used to provide quantitative measurements of the two-dimensional biofilm images. All three strains formed distinguishable biofilm architectures, indicating...

  6. The 'Swiss cheese' instability of bacterial biofilms

    CERN Document Server

    Jang, Hongchul; Stocker, Roman

    2012-01-01

    We demonstrate a novel pattern that results in bacterial biofilms as a result of the competition between hydrodynamic forces and adhesion forces. After the passage of an air plug, the break up of the residual thin liquid film scrapes and rearranges bacteria on the surface, such that a Swiss cheese pattern of holes is left in the residual biofilm.

  7. Cadmium Modulates Biofilm Formation by Staphylococcus epidermidis

    NARCIS (Netherlands)

    Wu, Xueqing; Santos, Regiane R.; Fink-Gremmels, Johanna

    2015-01-01

    The aim of the study was to evaluate the effect of cadmium exposure on Staphylococcus epidermidis (ATCC 35984) biofilm formation. Bacteria were cultured in the absence or presence of different concentrations (0-50 mu M) of cadmium. Biofilm formation and bacterial viability were assessed. Quantitativ

  8. Penetration of Rifampin through Staphylococcus epidermidis Biofilms

    OpenAIRE

    Zheng, Zhilan; Philip S. Stewart

    2002-01-01

    Rifampin penetrated biofilms formed by Staphylococcus epidermidis but failed to effectively kill the bacteria. Penetration was demonstrated by a simple diffusion cell bioassay and by transmission electron microscopic observation of antibiotic-affected cells at the distal edge of the biofilm.

  9. Screening of Compounds against Gardnerella vaginalis Biofilms.

    Directory of Open Access Journals (Sweden)

    Cornelia Gottschick

    Full Text Available Bacterial vaginosis (BV is a common infection in reproductive age woman and is characterized by dysbiosis of the healthy vaginal flora which is dominated by Lactobacilli, followed by growth of bacteria like Gardnerella vaginalis. The ability of G. vaginalis to form biofilms contributes to the high rates of recurrence that are typical for BV and which unfortunately make repeated antibiotic therapy inevitable. Here we developed a biofilm model for G. vaginalis and screened a large spectrum of compounds for their ability to prevent biofilm formation and to resolve an existing G. vaginalis biofilm. The antibiotics metronidazole and tobramycin were highly effective in preventing biofilm formation, but had no effect on an established biofilm. The application of the amphoteric tenside sodium cocoamphoacetate (SCAA led to disintegration of existing biofilms, reducing biomass by 51% and viability by 61% and it was able to increase the effect of metronidazole by 40% (biomass and 61% (viability. Our data show that attacking the biofilm and the bacterial cells by the combination of an amphoteric tenside with the antibiotic metronidazole might be a useful strategy against BV.

  10. Pseudomonas aeruginosa biofilms in cystic fibrosis

    DEFF Research Database (Denmark)

    Høiby, Niels; Ciofu, Oana; Bjarnsholt, Thomas

    2010-01-01

    The persistence of chronic Pseudomonas aeruginosa lung infections in cystic fibrosis (CF) patients is due to biofilm-growing mucoid (alginate-producing) strains. A biofilm is a structured consortium of bacteria, embedded in a self-produced polymer matrix consisting of polysaccharide, protein...

  11. Screening of Compounds against Gardnerella vaginalis Biofilms.

    Science.gov (United States)

    Gottschick, Cornelia; Szafranski, Szymon P; Kunze, Brigitte; Sztajer, Helena; Masur, Clarissa; Abels, Christoph; Wagner-Döbler, Irene

    2016-01-01

    Bacterial vaginosis (BV) is a common infection in reproductive age woman and is characterized by dysbiosis of the healthy vaginal flora which is dominated by Lactobacilli, followed by growth of bacteria like Gardnerella vaginalis. The ability of G. vaginalis to form biofilms contributes to the high rates of recurrence that are typical for BV and which unfortunately make repeated antibiotic therapy inevitable. Here we developed a biofilm model for G. vaginalis and screened a large spectrum of compounds for their ability to prevent biofilm formation and to resolve an existing G. vaginalis biofilm. The antibiotics metronidazole and tobramycin were highly effective in preventing biofilm formation, but had no effect on an established biofilm. The application of the amphoteric tenside sodium cocoamphoacetate (SCAA) led to disintegration of existing biofilms, reducing biomass by 51% and viability by 61% and it was able to increase the effect of metronidazole by 40% (biomass) and 61% (viability). Our data show that attacking the biofilm and the bacterial cells by the combination of an amphoteric tenside with the antibiotic metronidazole might be a useful strategy against BV. PMID:27111438

  12. Nanomaterials for the Treatment of Bacterial Biofilms.

    Science.gov (United States)

    Wang, Li-Sheng; Gupta, Akash; Rotello, Vincent M

    2016-01-01

    Treatment of biofilm-associated infections is challenging, requiring the development of new therapeutic strategies. In this viewpoint, we discuss the use of nanoparticle-based systems as active therapeutic agents and as vehicles to transport drugs to the site of infection. These applications require understanding of the surface interactions of nanoparticles with bacteria/biofilms, an aspect that we likewise summarize. PMID:27622944

  13. Biofilm ved kronisk rhinosinuitis og cystisk fibrose

    DEFF Research Database (Denmark)

    Fisker, Jacob; Buchwald, Christian von; Johansen, Helle Krogh

    2011-01-01

    Microbial biofilms are known to cause persistent foreign-body infections and have recently been acknowledged as involved in more than 65% of all human infections. Microbial biofilms have been detected in chronic rhinosinusitis, and chronic rhinosinusitis is mandatory in patients with cystic...

  14. Dental diagnostics: molecular analysis of oral biofilms.

    Science.gov (United States)

    Hiyari, Sarah; Bennett, Katie M

    2011-01-01

    Dental biofilms are complex, multi-species bacterial communities that colonize the mouth in the form of plaque and are known to cause dental caries and periodontal disease. Biofilms are unique from planktonic bacteria in that they are mutualistic communities with a 3-dimensional structure and complex nutritional and communication pathways. The homeostasis within the biofilm colony can be disrupted, causing a shift in the bacterial composition of the colony and resulting in proliferation of pathogenic species. Because of this dynamic lifestyle, traditional microbiological techniques are inadequate for the study of biofilms. Many of the bacteria present in the oral cavity are viable but not culturable, which severely limits laboratory analysis. However, with the advent of new molecular techniques, the microbial makeup of oral biofilms can be better identified. Some of these techniques include DNA-DNA hybridization, 16S rRNA gene sequencing, denaturing gradient gel electrophoresis, terminal restriction fragment length polymorphism, denaturing high-performance liquid chromatography and pyrosequencing. This review provides an overview of biofilm formation and examines the major molecular techniques currently used in oral biofilm analysis. Future applications of the molecular analysis of oral biofilms in the diagnosis and treatment of caries and periodontal disease are also discussed.

  15. Biofilms: The Stronghold of Legionella pneumophila

    Directory of Open Access Journals (Sweden)

    Mena Abdel-Nour

    2013-10-01

    Full Text Available Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation.

  16. Enzymatic removal and disinfection of bacterial biofilms

    DEFF Research Database (Denmark)

    Johansen, Charlotte; Falholt, Per; Gram, Lone

    1997-01-01

    -coated hydroxyapatite. The activity of enzymes against bacterial cells in biofilm was measured by fluorescence microscopy and an indirect conductance test in which evolution of carbon dioxide was measured. Glucose oxidase combined with lactoperoxidase was bactericidal against biofilm bacteria but did not remove...

  17. The Physics of Biofilms -- An Introduction

    CERN Document Server

    Mazza, Marco G

    2016-01-01

    Biofilms are complex, self-organized consortia of microorganisms that produce a functional, protective matrix of biomolecules. Physically, the structure of a biofilm can be described as an entangled polymer network which grows and changes under the effect of gradients of nutrients, cell differentiation, quorum sensing, bacterial motion, and interaction with the environment. Its development is complex, and constantly adapting to environmental stimuli. Here, we review the fundamental physical processes the govern the inception, growth and development of a biofilm. Two important mechanisms guide the initial phase in a biofilm life cycle: (\\emph{i}) the cell motility near or at a solid interface, and (\\emph{ii}) the cellular adhesion. Both processes are crucial for initiating the colony and for ensuring its stability. A mature biofilm behaves as a viscoelastic fluid with a complex, history-dependent dynamics. We discuss progress and challenges in the determination of its physical properties. Experimental and theo...

  18. Mesoscale Elucidation of Biofilm Shear Behavior

    CERN Document Server

    Barai, Pallab; Mukherjee, Partha P

    2015-01-01

    Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...

  19. The Extracellular Matrix of Fungal Biofilms.

    Science.gov (United States)

    Mitchell, Kaitlin F; Zarnowski, Robert; Andes, David R

    2016-01-01

    A key feature of biofilms is their production of an extracellular matrix. This material covers the biofilm cells, providing a protective barrier to the surrounding environment. During an infection setting, this can include such offenses as host cells and products of the immune system as well as drugs used for treatment. Studies over the past two decades have revealed the matrix from different biofilm species to be as diverse as the microbes themselves. This chapter will review the composition and roles of matrix from fungal biofilms, with primary focus on Candida species, Saccharomyces cerevisiae, Aspergillus fumigatus, and Cryptococcus neoformans. Additional coverage will be provided on the antifungal resistance proffered by the Candida albicans matrix, which has been studied in the most depth. A brief section on the matrix produced by bacterial biofilms will be provided for comparison. Current tools for studying the matrix will also be discussed, as well as suggestions for areas of future study in this field. PMID:27271680

  20. Oral biofilms: emerging concepts in microbial ecology.

    Science.gov (United States)

    Filoche, S; Wong, L; Sissons, C H

    2010-01-01

    Oral biofilms develop under a range of different conditions and different environments. This review will discuss emerging concepts in microbial ecology and how they relate to oral biofilm development and the treatment of oral diseases. Clues to how oral biofilms develop may lie in other complex systems, such as interactions between host and gut microbiota, and even in factors that affect biofilm development on leaf surfaces. Most of the conditions under which oral biofilms develop are tightly linked to the overall health and biology of the host. Advances in molecular techniques have led to a greater appreciation of the diversity of human microbiota, the extent of interactions with the human host, and how that relates to inter-individual variation. As a consequence, plaque development may no longer be thought of as a generic process, but rather as a highly individualized process, which has ramifications for the treatment of the diseases it causes.

  1. Biofilm-flow interactions in aquatic environments

    Science.gov (United States)

    Christensen, K. T.; Kazemifar, F.; Blois, G.; Aybar, M.; Perez Calleja, P.; Nerenberg, R.; Sinha, S.; Hardy, R. J.; Best, J.; Sambrook Smith, G.

    2015-12-01

    Biofilms are pervasive in aquatic environments, growing in pipes and channels in water supply systems, on permeable riverbeds, etc. The permeable, heterogeneous, and deformable structure of the biofilms make their interaction with surrounding fluid flow important from a range of perspectives, such as mass and momentum transport, and biofilm deformation and detachment due to shear stresses. Our understanding of these processes is limited, in part due to technical obstacles for performing such measurements. We have attempted to address these challenges using particle image velocimetry (PIV) and fluorescence imaging techniques in a water channel flow facility to obtain time-resolved velocity vector fields of flow around cylinders covered with biofilms at different growth stages. Analysis is focused on the coupled dynamics of turbulence and the biofilm development under different flow and nutrient conditions.

  2. The ecology and biogeochemistry of stream biofilms.

    Science.gov (United States)

    Battin, Tom J; Besemer, Katharina; Bengtsson, Mia M; Romani, Anna M; Packmann, Aaron I

    2016-04-01

    Streams and rivers form dense networks, shape the Earth's surface and, in their sediments, provide an immensely large surface area for microbial growth. Biofilms dominate microbial life in streams and rivers, drive crucial ecosystem processes and contribute substantially to global biogeochemical fluxes. In turn, water flow and related deliveries of nutrients and organic matter to biofilms constitute major constraints on microbial life. In this Review, we describe the ecology and biogeochemistry of stream biofilms and highlight the influence of physical and ecological processes on their structure and function. Recent advances in the study of biofilm ecology may pave the way towards a mechanistic understanding of the effects of climate and environmental change on stream biofilms and the biogeochemistry of stream ecosystems.

  3. In vitro phenotypic differentiation towards commensal and pathogenic oral biofilms

    NARCIS (Netherlands)

    Janus, M.M.; Keijser, B.J.F.; Bikker, F.J.; Exterkate, R.A.M.; Crielaard, W.; Krom, B.P.

    2015-01-01

    Commensal oral biofilms, defined by the absence of pathology-related phenotypes, are ubiquitously present. In contrast to pathological biofilms commensal biofilms are rarely studied. Here, the effect of the initial inoculum and subsequent growth conditions on in vitro oral biofilms was studied. Biof

  4. Discovering Biofilms: Inquiry-Based Activities for the Classroom

    Science.gov (United States)

    Redelman, Carly V.; Marrs, Kathleen; Anderson, Gregory G.

    2012-01-01

    In nature, bacteria exist in and adapt to different environments by forming microbial communities called "biofilms." We propose simple, inquiry-based laboratory exercises utilizing a biofilm formation assay, which allows controlled biofilm growth. Students will be able to qualitatively assess biofilm growth via staining. Recently, we developed a…

  5. Biofilm shows spatially stratified metabolic responses to contaminant exposure

    OpenAIRE

    Cao, Bin; Majors, Paul D.; Ahmed, Bulbul; Renslow, Ryan S.; Silvia, Crystal P.; Liang SHI; Kjelleberg, Staffan; Jim K. Fredrickson; Beyenal, Haluk

    2012-01-01

    Biofilms are core to a range of biological processes, including the bioremediation of environmental contaminants. Within a biofilm population, cells with diverse genotypes and phenotypes coexist, suggesting that distinct metabolic pathways may be expressed based on the local environmental conditions in a biofilm. However, metabolic responses to local environmental conditions in a metabolically active biofilm interacting with environmental contaminants have never been quantitatively elucidated...

  6. Biofilms On Orbit and On Earth: Current Methods, Future Needs

    Science.gov (United States)

    Vega, Leticia

    2013-01-01

    Biofilms have played a significant role on the effectiveness of life support hardware on the Space Shuttle and International Space Station (ISS). This presentation will discuss how biofilms impact flight hardware, how on orbit biofilms are analyzed from an engineering and research perspective, and future needs to analyze and utilize biofilms for long duration, deep space missions.

  7. Maltodextrin enhances biofilm elimination by electrochemical scaffold

    Science.gov (United States)

    Sultana, Sujala T.; Call, Douglas R.; Beyenal, Haluk

    2016-01-01

    Electrochemical scaffolds (e-scaffolds) continuously generate low concentrations of H2O2 suitable for damaging wound biofilms without damaging host tissue. Nevertheless, retarded diffusion combined with H2O2 degradation can limit the efficacy of this potentially important clinical tool. H2O2 diffusion into biofilms and bacterial cells can be increased by damaging the biofilm structure or by activating membrane transportation channels by exposure to hyperosmotic agents. We hypothesized that e-scaffolds would be more effective against Acinetobacter baumannii and Staphylococcus aureus biofilms in the presence of a hyperosmotic agent. E-scaffolds polarized at −600 mVAg/AgCl were overlaid onto preformed biofilms in media containing various maltodextrin concentrations. E-scaffold alone decreased A. baumannii and S. aureus biofilm cell densities by (3.92 ± 0.15) log and (2.31 ± 0.12) log, respectively. Compared to untreated biofilms, the efficacy of the e-scaffold increased to a maximum (8.27 ± 0.05) log reduction in A. baumannii and (4.71 ± 0.12) log reduction in S. aureus biofilm cell densities upon 10 mM and 30 mM maltodextrin addition, respectively. Overall ~55% decrease in relative biofilm surface coverage was achieved for both species. We conclude that combined treatment with electrochemically generated H2O2 from an e-scaffold and maltodextrin is more effective in decreasing viable biofilm cell density. PMID:27782161

  8. Combined Reactor and Microelectrode Measurements in Laboratory Grown Biofilms

    DEFF Research Database (Denmark)

    Larsen, Tove; Harremoës, Poul

    1994-01-01

    were carried out with aerobic glucose and starch degrading biofilms. The well described aerobic glucose degradation biofilm system was used to test the combined reactor set-up. Results predicted from known biofilm kinetics were obtained. In the starch degrading biofilm, basic assumptions were tested......A combined biofilm reactor-/microelectrode experimental set-up has been constructed, allowing for simultaneous reactor mass balances and measurements of concentration profiles within the biofilm. The system consists of an annular biofilm reactor equipped with an oxygen microelectrode. Experiments...

  9. Antibiotic resistance in Pseudomonas aeruginosa biofilms: towards the development of novel anti-biofilm therapies.

    Science.gov (United States)

    Taylor, Patrick K; Yeung, Amy T Y; Hancock, Robert E W

    2014-12-10

    The growth of bacteria as structured aggregates termed biofilms leads to their protection from harsh environmental conditions such as physical and chemical stresses, shearing forces, and limited nutrient availability. Because of this highly adapted ability to survive adverse environmental conditions, bacterial biofilms are recalcitrant to antibiotic therapies and immune clearance. This is particularly problematic in hospital settings where biofilms are a frequent cause of chronic and device-related infections and constitute a significant burden on the health-care system. The major therapeutic strategy against infections is the use of antibiotics, which, due to adaptive resistance, are often insufficient to clear biofilm infections. Thus, novel biofilm-specific therapies are required. Specific features of biofilm development, such as surface adherence, extracellular matrix formation, quorum sensing, and highly regulated biofilm maturation and dispersal are currently being studied as targets to be exploited in the development of novel biofilm-specific treatments. Using Pseudomonas aeruginosa for illustrative purposes, this review highlights the antibiotic resistance mechanisms of biofilms, and discusses current research into novel biofilm-specific therapies.

  10. Planktonic versus biofilm catabolic communities: importance of the biofilm for species selection and pesticide degradation.

    Science.gov (United States)

    Verhagen, Pieter; De Gelder, Leen; Hoefman, Sven; De Vos, Paul; Boon, Nico

    2011-07-01

    Chloropropham-degrading cultures were obtained from sludge and soil samples by using two different enrichment techniques: (i) planktonic enrichments in shaken liquid medium and (ii) biofilm enrichments on two types of solid matrixes (plastic chips and gravel). Denaturing gradient gel electrophoresis fingerprinting showed that planktonic and biofilm cultures had a different community composition depending on the presence and type of added solid matrix during enrichment. This was reflected in the unique chloropropham-degrading species that could be isolated from the different cultures. Planktonic and biofilm cultures also differed in chloropropham-degrading activity. With biofilm cultures, slower chloropropham removal was observed, but with less build-up of the toxic intermediate 3-chloroaniline. Disruption of the biofilm architecture resulted in degradation characteristics shifting toward those of the free suspensions, indicating the importance of a well-established biofilm structure for good performance. These results show that biofilm-mediated enrichment techniques can be used to select for pollutant-degrading microorganisms that like to proliferate in a biofilm and that cannot be isolated using conventional shaken-liquid procedures. Furthermore, the influence of the biofilm architecture on the pesticide degradation characteristics suggests that for bioaugmentation the use of biofilm catabolic communities might be a proficient alternative to using planktonic freely suspended cultures. PMID:21602394

  11. Plaque biofilms: the effect of chemical environment on natural human plaque biofilm architecture.

    Science.gov (United States)

    Robinson, C; Strafford, S; Rees, G; Brookes, S J; Kirkham, J; Shore, R C; Watson, P S; Wood, S

    2006-11-01

    The architecture of microbial biofilms especially the outer regions have an important influence on the interaction between biofilm and local environment particularly on the flux of materials into and out of biofilm compartments and as a consequence, biofilm metabolic behaviour. In the case of dental plaque biofilms, architecture will determine access of nutrients including acidogenic substrates and therapeutic materials to the microbial biomass and to the underlying tooth surface. Manipulation of this architecture may offer a means of altering mass transfer into the whole biofilm and biomass and raises the possibility of improving access of therapeutics. Plaque biofilms formed in vivo on human enamel were subjected to a number of different chemical conditions while under observation by confocal laser scanning microscopy in reflection mode. In this way the outer 50-100 microm or so of the biofilms was examined. Density and distribution of biomass were recorded as degree of reflectance. The amount and density of biofilm biomass increased from the plaque saliva interface towards the interior. Plaque biofilms were robust and little affected by mechanical manipulation, high ionic strength or low pH (2.5). Detergent (SLS), however, often appeared to either remove biomass and/or dramatically reduce its density.

  12. Osteopontin reduces biofilm formation in a multi-species model of dental biofilm.

    Directory of Open Access Journals (Sweden)

    Sebastian Schlafer

    Full Text Available BACKGROUND: Combating dental biofilm formation is the most effective means for the prevention of caries, one of the most widespread human diseases. Among the chemical supplements to mechanical tooth cleaning procedures, non-bactericidal adjuncts that target the mechanisms of bacterial biofilm formation have gained increasing interest in recent years. Milk proteins, such as lactoferrin, have been shown to interfere with bacterial colonization of saliva-coated surfaces. We here study the effect of bovine milk osteopontin (OPN, a highly phosphorylated whey glycoprotein, on a multispecies in vitro model of dental biofilm. While considerable research effort focuses on the interaction of OPN with mammalian cells, there are no data investigating the influence of OPN on bacterial biofilms. METHODOLOGY/PRINCIPAL FINDINGS: Biofilms consisting of Streptococcus oralis, Actinomyces naeslundii, Streptococcus mitis, Streptococcus downei and Streptococcus sanguinis were grown in a flow cell system that permitted in situ microscopic analysis. Crystal violet staining showed significantly less biofilm formation in the presence of OPN, as compared to biofilms grown without OPN or biofilms grown in the presence of caseinoglycomacropeptide, another phosphorylated milk protein. Confocal microscopy revealed that OPN bound to the surface of bacterial cells and reduced mechanical stability of the biofilms without affecting cell viability. The bacterial composition of the biofilms, determined by fluorescence in situ hybridization, changed considerably in the presence of OPN. In particular, colonization of S. mitis, the best biofilm former in the model, was reduced dramatically. CONCLUSIONS/SIGNIFICANCE: OPN strongly reduces the amount of biofilm formed in a well-defined laboratory model of acidogenic dental biofilm. If a similar effect can be observed in vivo, OPN might serve as a valuable adjunct to mechanical tooth cleaning procedures.

  13. Inactivation of Efflux Pumps Abolishes Bacterial Biofilm Formation

    DEFF Research Database (Denmark)

    Kvist, Malin; Hancock, Viktoria; Klemm, Per

    2008-01-01

    to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial biofilms, thus making efflux pumps attractive targets for antibiofilm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofilm formation, and in combination they could...... abolish biofilm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofilms. The results of this feasibility study might pave the way for new treatments for biofilm-related infections and may be exploited for prevention of biofilms in general.......Bacterial biofilms cause numerous problems in health care and industry; notably, biofilms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps...

  14. Intrigues of biofilm: A perspective in veterinary medicine.

    Science.gov (United States)

    Abdullahi, Umar Faruk; Igwenagu, Ephraim; Mu'azu, Anas; Aliyu, Sani; Umar, Maryam Ibrahim

    2016-01-01

    Biofilm has a tremendous impact in the field of veterinary medicine, especially the livestock industry, leading to a serious economic loss. Over the years, little attention has been given to biofilm in animals with most of the research geared toward human biofilm diseases. The greatest challenge posed by biofilm is in its incredible ability to resist most of the currently existing antibiotics. This mystery can best be demystified through understanding the mechanism of the quorum sensing which regulate the pathophysiology of biofilm. Ability of biofilm formation in a variety of inanimate surfaces such as animal food contact surfaces is responsible for a host of biofilm diseases affecting animals and humans. In this review, we highlighted some of the challenges of biofilm in livestock and food industries. Also highlighted are; mechanisms of biofilm development, best diagnostic approach and possible novel therapeutic measures needed to combat the menace of biofilm in veterinary medicine.

  15. Intrigues of biofilm: A perspective in veterinary medicine

    Directory of Open Access Journals (Sweden)

    Umar Faruk Abdullahi

    2016-01-01

    Full Text Available Biofilm has a tremendous impact in the field of veterinary medicine, especially the livestock industry, leading to a serious economic loss. Over the years, little attention has been given to biofilm in animals with most of the research geared toward human biofilm diseases. The greatest challenge posed by biofilm is in its incredible ability to resist most of the currently existing antibiotics. This mystery can best be demystified through understanding the mechanism of the quorum sensing which regulate the pathophysiology of biofilm. Ability of biofilm formation in a variety of inanimate surfaces such as animal food contact surfaces is responsible for a host of biofilm diseases affecting animals and umans. In this review, we highlighted some of the challenges of biofilm in livestock and food industries. Also highlighted are; mechanisms of biofilm development, best diagnostic approach and possible novel therapeutic measures needed to combat the menace of biofilm in veterinary medicine.

  16. Removal of Burkholderia cepacia biofilms with oxidants

    Science.gov (United States)

    Koenig, D. W.; Mishra, S. K.; Pierson, D. L.

    1995-01-01

    Iodine is used to disinfect the water system aboard US space shuttles and is the anticipated biocide for the international space station. Water quality on spacecraft must be maintained at the highest possible levels for the safety of the crew. Furthermore, the treatment process used to maintain the quality of water on research must be robust and operate for long periods with minimal crew intervention. Biofilms are recalcitrant and pose a major threat with regard to chronic contamination of spacecraft water systems. We measured the effectiveness of oxidizing biocides on the removal and regrowth of Burkholderia (Pseudomonas) cepacia biofilms. B. cepacia, isolated from the water distribution system of the space shuttle Discovery, was grown in continuous culture to produce a bacterial contamination source for biofilm formation and removal studies. A 10(7) CFU ml-1 B. cepacia suspension, in distilled water, was used to form biofilms on 3000 micrometers2 glass surfaces. Rates of attachment were measured directly with image analysis and were found to be 7.8, 15.2, and 22.8 attachment events h-1 for flow rates of 20.7, 15.2, and 9.8 ml min-1, respectively. After 18 h of formation, the B. cepacia biofilms were challenged with oxidants (ozone, chlorine, and iodine) and the rates of biofilm removal determined by image analysis. Fifty percent of the biofilm material was removed in the first hour of continous treatment with 24 mg l-1 chlorine or 2 mg l-1 ozone. Iodine (48 mg l-1) did not remove any measurable cellular material after 6 h continuous contact. After this first removal of biofilms by the oxidants, the surface was allowed to refoul and was again treated with the biocide. Iodine was the only compound that was unable to remove cellular debris from either primary or secondary biofilms. Moreover, treating primary biofilms with iodine increased the rate of formation of secondary biofilms, from 4.4 to 5.8 attachment events h-1. All the oxidants tested inactivated the B

  17. Microbial Biofilms in Endodontic Infections: An Update Review

    OpenAIRE

    Zahed Mohammadi; Flavio Palazzi; Luciano Giardino; Sousan Shalavi

    2013-01-01

    Biofilms and microbial aggregates are the common mechanisms for the survival of bacteria in nature. In other words, the ability to form biofilms has been regarded as a virulence factor. Microbial biofilms play an essential role in several infectious diseases such as pulp and periradicular pathosis. The aim of this article was to review the adaptation mechanisms of biofilms, their roles in pulpal and periapical pathosis, factors influencing biofilm formation, mechanisms of their antimicrobial ...

  18. Analyse der postoperativen Versorgung von Patienten mit proximaler Femurfraktur in einer Rehabilitationsklinik

    OpenAIRE

    Dreßler, Simone Anneliese

    2009-01-01

    Osteoporotische Frakturen sind im Zusammenhang mit proximalen Femurfrakturen beim älteren Menschen von hoher klinischer und sozioökonomischer Bedeutung. Trotz des weltweiten exponentiellen Anstiegs osteoporotischer Fakturen findet vor allem in den primär versorgenden Kliniken eine Identifizierung und adäquate Behandlung von Patienten mit hohem Risiko nur unzureichend statt. Es besteht eine hohe Variabilität innerhalb der Versorgung osteoporotischer Patienten mit PFF in der Rehabilitationsklin...

  19. Auslegung und Optimierung von Flanschverbindungen mit SMC-Losflanschen und PTFE-Dichtungen

    OpenAIRE

    Kurz, Hariolf

    2014-01-01

    Die Anforderungen an Rohrleitungen aus glasfaserverstärktem Kunststoff (GFK) sind im Hinblick auf die Dichtheit, die Medienbeständigkeit und die Betriebssicherheit in den letzten Jahren gestiegen. Dennoch müssen die Betreiber chemischer Anlagen mit Rohrleitungen aus glasfaserverstärktem Kunststoff mit Losflanschen aus sheet-molding-compound (SMC) diese nachweislich sicher betreiben. Die Motivation zu dieser Arbeit liegt darin, dieses Bestreben mit der Auswahl von geeigneten PTFE-Dichtungen un...

  20. Regelung von Robotern mit elastischen Gelenken am Beispiel der DLR-Leichtbauarme

    OpenAIRE

    Albu-Schäffer, Alin

    2007-01-01

    In der Arbeit werden Methoden zur Parameteridentifikation und Regelung von Robotern mit elastischen Gelenken vorgeschlagen, am Beispiel der DLR-Leichtbauroboter experimentell implementiert und im Dauereinsatz validiert. Das Modell des Manipulators mit elastischen Gelenken trifft sowohl für schnell bewegte Industrieroboter, wie auch für extrem leichte Roboter im Service- oder Raumfahrtbereich zu. Ausgehend von einem Gelenk-Zustandsregler mit konstanten Parametern und Kompensation der Starrkörp...

  1. Untersuchung von Verbesserungspotentialen hinsichtlich Verbrauch und Drehmoment bei Ottomotoren mit Hilfe 1-dimensionaler Simulationsrechnung

    OpenAIRE

    Schreiber, Gert

    2006-01-01

    Im Rahmen dieser Arbeit wurden verschiedene Verbesserungspotentiale von Ottomotoren mit besonderer Berücksichtigung von Verbrauch und Drehmoment mit Hilfe der Motorprozeßrechnung untersucht. Insbesondere wurden die Zusammenhänge von Ursache und Wirkung einzelner Verbesserungsmaßnahmen herausgestellt. Zur Modellierung realer Motoren wurde die Simulationssoftware GT-Power verwendet, wobei die Regelung über Matlab/Simulink vorgenommen wurde. Aber auch mit vereinfachten Rechenmodellen, die unter ...

  2. Quantitative Datenanalyse: Arbeiten mit SPSS Statistics : Eine Einführung

    OpenAIRE

    Hoidn, Sabine

    2012-01-01

    Bei diesem Buch handelt es sich um eine verständliche Einführung in das Arbeiten mit dem quantitativen Datenanalyseprogramm SPSS Statistics. Die Studierenden setzen sich mit den Grundlagen zum Arbeiten mit SPSS Statistics auseinander, können selbständig eine SPSS Statistics-Datei erstellen, Daten einlesen, zusammenfügen und modifizieren, erfasste Daten managen und die gebräuchlichsten tabellarischen und grafischen Grundauswertungen sowie Analyseverfahren durchführen und interpretieren. Au...

  3. Biofilm-specific extracellular matrix proteins of nontypeable Haemophilus influenzae.

    Science.gov (United States)

    Wu, Siva; Baum, Marc M; Kerwin, James; Guerrero, Debbie; Webster, Simon; Schaudinn, Christoph; VanderVelde, David; Webster, Paul

    2014-12-01

    Nontypeable Haemophilus influenzae (NTHi), a human respiratory tract pathogen, can form colony biofilms in vitro. Bacterial cells and the amorphous extracellular matrix (ECM) constituting the biofilm can be separated using sonication. The ECM from 24- and 96-h NTHi biofilms contained polysaccharides and proteinaceous components as detected by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) spectroscopy. More conventional chemical assays on the biofilm ECM confirmed the presence of these components and also DNA. Proteomics revealed eighteen proteins present in biofilm ECM that were not detected in planktonic bacteria. One ECM protein was unique to 24-h biofilms, two were found only in 96-h biofilms, and fifteen were present in the ECM of both 24- and 96-h NTHi biofilms. All proteins identified were either associated with bacterial membranes or cytoplasmic proteins. Immunocytochemistry showed two of the identified proteins, a DNA-directed RNA polymerase and the outer membrane protein OMP P2, associated with bacteria and biofilm ECM. Identification of biofilm-specific proteins present in immature biofilms is an important step in understanding the in vitro process of NTHi biofilm formation. The presence of a cytoplasmic protein and a membrane protein in the biofilm ECM of immature NTHi biofilms suggests that bacterial cell lysis may be a feature of early biofilm formation.

  4. The MIT TEAL Simulations and Visualizations in Electromagnetism

    Science.gov (United States)

    Belcher, John

    2007-03-01

    The Technology Enabled Active Learning (TEAL) Project at MIT has developed a broad range of 3D visualizations and simulations to foster student intuition about electromagnetic fields and phenomena (see http://web.mit.edu/8.02t/www/802TEAL3D/). In this talk we discuss the software approaches we use to create these simulations, including Macromedia Shockwave and Java 3D applets for interactive visualization, passive animations created with 3ds max, and the Dynamic Line Integral Convolution (DLIC) method for constructing time dependent representations of the electromagnetic field at close to the resolution of the computer display (Sundquist, 2003). The DLIC method, in particular, is far superior in delineating the spatial and temporal structure of fields as compared to e.g. field line displays or vector field grids. We also report on the use of these visualizations in instruction at the freshmen level. Our strong opinion is that for effective student learning, such visualizations must be embedded in a software framework for their interactive delivery. This ``guided inquiry'' framework is essential to influence and optimize what students take away from the visualizations. In our current research, we are delivering our visualizations using a commercial package, Addison Wesley's MasteringPhysics (MP), although any guided inquiry delivery system such as MP will be able to interact with our simulation software. We have released our Java 3D simulation software as open source with a liberal open source license (see http://jlearn.mit.edu/tealsim/ ), with support from the Davis Educational Foundation.

  5. Microfluidic Approaches to Bacterial Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Hee-Deung Park

    2012-08-01

    Full Text Available Bacterial biofilms—aggregations of bacterial cells and extracellular polymeric substrates (EPS—are an important subject of research in the fields of biology and medical science. Under aquatic conditions, bacterial cells form biofilms as a mechanism for improving survival and dispersion. In this review, we discuss bacterial biofilm development as a structurally and dynamically complex biological system and propose microfluidic approaches for the study of bacterial biofilms. Biofilms develop through a series of steps as bacteria interact with their environment. Gene expression and environmental conditions, including surface properties, hydrodynamic conditions, quorum sensing signals, and the characteristics of the medium, can have positive or negative influences on bacterial biofilm formation. The influences of each factor and the combined effects of multiple factors may be addressed using microfluidic approaches, which provide a promising means for controlling the hydrodynamic conditions, establishing stable chemical gradients, performing measurement in a high-throughput manner, providing real-time monitoring, and providing in vivo-like in vitro culture devices. An increased understanding of biofilms derived from microfluidic approaches may be relevant to improving our understanding of the contributions of determinants to bacterial biofilm development.

  6. Iron and Acinetobacter baumannii Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Valentina Gentile

    2014-08-01

    Full Text Available Acinetobacter baumannii is an emerging nosocomial pathogen, responsible for infection outbreaks worldwide. The pathogenicity of this bacterium is mainly due to its multidrug-resistance and ability to form biofilm on abiotic surfaces, which facilitate long-term persistence in the hospital setting. Given the crucial role of iron in A. baumannii nutrition and pathogenicity, iron metabolism has been considered as a possible target for chelation-based antibacterial chemotherapy. In this study, we investigated the effect of iron restriction on A. baumannii growth and biofilm formation using different iron chelators and culture conditions. We report substantial inter-strain variability and growth medium-dependence for biofilm formation by A. baumannii isolates from veterinary and clinical sources. Neither planktonic nor biofilm growth of A. baumannii was affected by exogenous chelators. Biofilm formation was either stimulated by iron or not responsive to iron in the majority of isolates tested, indicating that iron starvation is not sensed as an overall biofilm-inducing stimulus by A. baumannii. The impressive iron withholding capacity of this bacterium should be taken into account for future development of chelation-based antimicrobial and anti-biofilm therapies.

  7. Crenarchaeal biofilm formation under extreme conditions.

    Directory of Open Access Journals (Sweden)

    Andrea Koerdt

    Full Text Available BACKGROUND: Biofilm formation has been studied in much detail for a variety of bacterial species, as it plays a major role in the pathogenicity of bacteria. However, only limited information is available for the development of archaeal communities that are frequently found in many natural environments. METHODOLOGY: We have analyzed biofilm formation in three closely related hyperthermophilic crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus and S. tokodaii. We established a microtitre plate assay adapted to high temperatures to determine how pH and temperature influence biofilm formation in these organisms. Biofilm analysis by confocal laser scanning microscopy demonstrated that the three strains form very different communities ranging from simple carpet-like structures in S. solfataricus to high density tower-like structures in S. acidocaldarius in static systems. Lectin staining indicated that all three strains produced extracellular polysaccharides containing glucose, galactose, mannose and N-acetylglucosamine once biofilm formation was initiated. While flagella mutants had no phenotype in two days old static biofilms of S. solfataricus, a UV-induced pili deletion mutant showed decreased attachment of cells. CONCLUSION: The study gives first insights into formation and development of crenarchaeal biofilms in extreme environments.

  8. Fractal analysis of Xylella fastidiosa biofilm formation

    Science.gov (United States)

    Moreau, A. L. D.; Lorite, G. S.; Rodrigues, C. M.; Souza, A. A.; Cotta, M. A.

    2009-07-01

    We have investigated the growth process of Xylella fastidiosa biofilms inoculated on a glass. The size and the distance between biofilms were analyzed by optical images; a fractal analysis was carried out using scaling concepts and atomic force microscopy images. We observed that different biofilms show similar fractal characteristics, although morphological variations can be identified for different biofilm stages. Two types of structural patterns are suggested from the observed fractal dimensions Df. In the initial and final stages of biofilm formation, Df is 2.73±0.06 and 2.68±0.06, respectively, while in the maturation stage, Df=2.57±0.08. These values suggest that the biofilm growth can be understood as an Eden model in the former case, while diffusion-limited aggregation (DLA) seems to dominate the maturation stage. Changes in the correlation length parallel to the surface were also observed; these results were correlated with the biofilm matrix formation, which can hinder nutrient diffusion and thus create conditions to drive DLA growth.

  9. Alternating Current Influences Anaerobic Electroactive Biofilm Activity.

    Science.gov (United States)

    Wang, Xin; Zhou, Lean; Lu, Lu; Lobo, Fernanda Leite; Li, Nan; Wang, Heming; Park, Jaedo; Ren, Zhiyong Jason

    2016-09-01

    Alternating current (AC) is known to inactivate microbial growth in suspension, but how AC influences anaerobic biofilm activities has not been systematically investigated. Using a Geobacter dominated anaerobic biofilm growing on the electrodes of microbial electrochemical reactors, we found that high frequency AC ranging from 1 MHz to 1 kHz (amplitude of 5 V, 30 min) showed only temporary inhibition to the biofilm activity. However, lower frequency (100 Hz, 1.2 or 5 V) treatment led to 47 ± 19% permanent decrease in limiting current on the same biofilm, which is attributed to the action of electrohydrodynamic force that caused biofilm damage and loss of intercellular electron transfer network. Confocal microscopy images show such inactivation mainly occurred at the interface between the biofilm and the electrode. Reducing the frequency further to 1 Hz led to water electrolysis, which generated gas bubbles that flushed all attached cells out of the electrode. These findings provide new references on understanding and regulating biofilm growth, which has broader implications in biofouling control, anaerobic waste treatment, energy and product recovery, and general understanding of microbial ecology and physiology. PMID:27485403

  10. Biofilms in Infections of the Eye

    Directory of Open Access Journals (Sweden)

    Paulo J. M. Bispo

    2015-03-01

    Full Text Available The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority.

  11. Oral biofilm architecture on natural teeth.

    Directory of Open Access Journals (Sweden)

    Vincent Zijnge

    Full Text Available Periodontitis and caries are infectious diseases of the oral cavity in which oral biofilms play a causative role. Moreover, oral biofilms are widely studied as model systems for bacterial adhesion, biofilm development, and biofilm resistance to antibiotics, due to their widespread presence and accessibility. Despite descriptions of initial plaque formation on the tooth surface, studies on mature plaque and plaque structure below the gum are limited to landmark studies from the 1970s, without appreciating the breadth of microbial diversity in the plaque. We used fluorescent in situ hybridization to localize in vivo the most abundant species from different phyla and species associated with periodontitis on seven embedded teeth obtained from four different subjects. The data showed convincingly the dominance of Actinomyces sp., Tannerella forsythia, Fusobacterium nucleatum, Spirochaetes, and Synergistetes in subgingival plaque. The latter proved to be new with a possibly important role in host-pathogen interaction due to its localization in close proximity to immune cells. The present study identified for the first time in vivo that Lactobacillus sp. are the central cells of bacterial aggregates in subgingival plaque, and that Streptococcus sp. and the yeast Candida albicans form corncob structures in supragingival plaque. Finally, periodontal pathogens colonize already formed biofilms and form microcolonies therein. These in vivo observations on oral biofilms provide a clear vision on biofilm architecture and the spatial distribution of predominant species.

  12. Oral biofilm architecture on natural teeth.

    Science.gov (United States)

    Zijnge, Vincent; van Leeuwen, M Barbara M; Degener, John E; Abbas, Frank; Thurnheer, Thomas; Gmür, Rudolf; Harmsen, Hermie J M

    2010-02-24

    Periodontitis and caries are infectious diseases of the oral cavity in which oral biofilms play a causative role. Moreover, oral biofilms are widely studied as model systems for bacterial adhesion, biofilm development, and biofilm resistance to antibiotics, due to their widespread presence and accessibility. Despite descriptions of initial plaque formation on the tooth surface, studies on mature plaque and plaque structure below the gum are limited to landmark studies from the 1970s, without appreciating the breadth of microbial diversity in the plaque. We used fluorescent in situ hybridization to localize in vivo the most abundant species from different phyla and species associated with periodontitis on seven embedded teeth obtained from four different subjects. The data showed convincingly the dominance of Actinomyces sp., Tannerella forsythia, Fusobacterium nucleatum, Spirochaetes, and Synergistetes in subgingival plaque. The latter proved to be new with a possibly important role in host-pathogen interaction due to its localization in close proximity to immune cells. The present study identified for the first time in vivo that Lactobacillus sp. are the central cells of bacterial aggregates in subgingival plaque, and that Streptococcus sp. and the yeast Candida albicans form corncob structures in supragingival plaque. Finally, periodontal pathogens colonize already formed biofilms and form microcolonies therein. These in vivo observations on oral biofilms provide a clear vision on biofilm architecture and the spatial distribution of predominant species.

  13. Aging biofilm from a full-scale moving bed biofilm reactor: characterization and enzymatic treatment study.

    Science.gov (United States)

    Huang, Hui; Ren, Hongqiang; Ding, Lili; Geng, Jinju; Xu, Ke; Zhang, Yan

    2014-02-01

    Effective removal of aging biofilm deserves to receive more attention. This study aimed to characterized aging biofilm from a full-scale moving bed biofilm reactor treating pharmaceutical wastewater and evaluate the hydrolysis effects of biofilm by different enzymatic treatments. Results from FTIR and biochemical composition analyses showed that it was a predominately organic-based biofilm with the ratio of total protein (PN) to polysaccharide (PS) of 20.17. A reticular structure of extracellular polymeric matrix (EPM) with filamentous bacteria as the skeleton was observed on the basal layer through SEM-EDS test. Among the four commercial proteases and amylases from Genencor®, proteases were shown to have better performances than amylases either on the removal of MLSS and PN/MLSS or on DOC (i.e., dissolved organic carbon)/MLSS raising of biofilm pellets. Difference of dynamic fluorescence characteristics of dissolved organic matters after treated by the two proteases indicated distinguishing mechanisms of the treating process.

  14. Treatment of Oral Multispecies Biofilms by an Anti-Biofilm Peptide.

    Directory of Open Access Journals (Sweden)

    Zhejun Wang

    Full Text Available Human oral biofilms are multispecies microbial communities that exhibit high resistance to antimicrobial agents. Dental plaque gives rise to highly prevalent and costly biofilm-related oral infections, which lead to caries or other types of oral infections. We investigated the ability of the recently identified anti-biofilm peptide 1018 to induce killing of bacterial cells present within oral multispecies biofilms. At 10 μg/ml (6.5 μM, peptide 1018 was able to significantly (p50% of the biofilm being killed and >35% being dispersed in only 3 minutes. Peptide 1018 may potentially be used by itself or in combination with CHX as a non-toxic and effective anti-biofilm agent for plaque disinfection in clinical dentistry.

  15. Vergleich der Narbenausprägung und Bewertung der Kosmetik bei Patientinnen mit brusterhaltend operiertem Mammakarzinom und einseitiger Strahlenbehandlung nach simultaner Reduktionsmastektomie beidseits

    OpenAIRE

    Gatti, Alessia

    2014-01-01

    Mit der hier vorgelegten Arbeit sollte im Hinblick auf die Narbenbildung der Einfluss der alleinigen Operation verglichen werden mit dem Effekt einer Operation plus adjuvanter Strahlentherapie. Dazu wurde ein Patientinnenkollektiv mit bilateraler Operation, aber unilateraler Strahlenbehandlung ausgewählt. Diese Bedingungen sind bei Patientinnen mit unilateralem Mammakarzinom und gleichzeitiger beidseitiger Reduktionsmastektomie gegeben. Mit der beidseitigen Reduktionsmastektomie wird auf der ...

  16. The MIT – Cornell Collision and Why It Happened

    OpenAIRE

    Fletcher, Luke Sebastian; Teller, Seth; Olson, Edwin B.; Moore, David C.; Kuwata, Yoshiaki; How, Jonathan P.; Leonard, John Joseph; Miller, Isaac; Campbell, Mark; Huttenlocher, Dan; Nathan, Aaron; Kline, Frank-Robert

    2009-01-01

    Mid-way through the 2007 DARPA Urban Challenge, MIT’s autonomous Land Rover LR3 ‘Talos’ and Team Cornell’s autonomous Chevrolet Tahoe ‘Skynet’ collided in a low-speed accident, one of the first well-documented collisions between two full-size autonomous vehicles. This collaborative study between MIT and Cornell examines the root causes of the collision, which are identified in both teams’ system designs. Systems-level descriptions of both autonomous vehicles are given, and a...

  17. A Single Channel Measurement Svstem For Brain MIT

    Institute of Scientific and Technical Information of China (English)

    QINMing-xing; JIAOLi-cheng; WANGCong; LIShi-jun; DONGXiu-zhen; LUHua

    2004-01-01

    A single channel measurement system for brain MIT has been built. The system is composed of an exciting source unit, a detecting unit, a rotating and controlling unit, and imaging unit. The experiment results of single channel measurements show that the system output versus the conductivity of the objects was an approximate linear relationship when the diameter of an object was about 9cm and its conductivity was in 0.1 S/m, 0.7 S/m, 2S/m, 6S/m. The sensitivit yof the phase detector was 53 mV/degree from -10 to+10 degree.

  18. Innovative facades with photovoltaics; Innovative Fassaden mit Photovoltaik

    Energy Technology Data Exchange (ETDEWEB)

    Eicker, U. [Hochschule fuer Technik, Stuttgart (Germany)

    1999-10-01

    Having grown at a rate of 15% since the middle of the 1980s the photovoltaic market today commands an annual module production of more than 100 MW{sub p}. In Germany altogether 10,000 PV systems with a total power output of 10 MW{sub p} were newly installed in 1997 alone. In 1990 the market was boosted by the heavily subsidised 1000 roofs programme, under which in the end more than 2,000 systems were installed on the roofs of mostly one-family houses. With power ratings ranging from 1 to 5 kW these decentral plants require roof surface areas between 10 and 50 m-2. On average they generate 800 kWh of electricity per kW of installed power. According to a number of studies carried out in the early 1990s the total surface area on buildings available for photovoltaics amounts to an enormous potential of 1,000 km-2, which is equivalent to an electricity generating potential of 130 TWh (100 TWh on roofs and 30 TWh on facades), or 25% of Germany`s total electricity demand. The degree to which this potential will be realised in the long term will notably depend on whether convincing architectural solutions are found for integrating photovoltaic plants in roofs and facades. [Deutsch] Der Photovoltaikmarkt waechst weltweit seit Mitte der 80er Jahre um durchschnittlich 15% und liegt heute bei einer Jahresmodulproduktion ueber 100 MW{sub p}. In Deutschland wurden alleine 1997 etwa 10.000 PV-Systeme mit einer Gesamtleistung von 10 MW{sub p} installiert. Die Marktentwicklung wurde 1990 mit dem stark subventionierten 1000-Daecher Programm angestossen, in welchem schliesslich mehr als 2000 Systeme meist auf Daechern von Einfamilienhaeusern installiert wurden. Diese dezentralen Anlagen mit Leistungen zwischen 1 und 5 kW erfordern Dachflaechen zwischen 10 und 50 m{sup 2} und erzeugen im Schnitt 800 kWh Strom pro kW installierter Leistung. Das verfuegbare Flaechenpotential von Gebaeuden wurde Anfang der 90er Jahre in einer Reihe von Studien ermittelt und stellt mit etwa 1000 km{sup 2

  19. Sicheres Navigieren in dynamischen Umgebungen mit 3D-Kollisionsvermeidung

    Science.gov (United States)

    Stiene, Stefan; Hertzberg, Joachim

    Diese Papier stellt eine neuartige Methode vor, die 3D-Hindernisvermeidung ermöglicht. Die Sensorkonfiguration beruht auf sechs Laserscannern, die die gesamte Roboteroberfläche abdecken. Die Daten der sechs Laserscanner werden zu einem virtuellen, zweidimensionalen, horizontal ausgerichteten 360°-Laserscanner kombiniert. Da der virtuelle Laserscanner die 3D-Umgebung in einem zweidimensionalen Datensatz repräsentiert, ermöglicht er in Kombination mit klassischen Hindernisvermeidungsalgorithmen wie der Vector Field Histogram Methode eine 3D-Hindernisvermeidung.

  20. Mit Mathematik zu Mehr Intelligenz in der Logistik

    Science.gov (United States)

    Möhring, Rolf H.; Schenk, Michael

    Die Lösung logistischer Probleme ist ein wichtiger Aspekt menschlichen Handelns seit Menschen gemeinsam zielgerichtet tätig wurden. Die Grundlagen dessen, was wir heute Logistik nennen, entstammen dem militärischen Bereich. So basierte z. B. das römische Imperium in starkem Maße auf militärisch-logistischen Glanzleistungen. Ob damals bereits mathematische Überlegungen eine Rolle spielten, wissen wir heute nicht. Jedoch versuchte z. B. Napoleon, der mit den bedeutendsten Mathematikern seiner Zeit befreundet war, den Transport seiner Truppen und die Verbreitung von Informationen zu optimieren und strategisch einzusetzen.1,2

  1. Befunde und Therapie bei 461 Kühen mit Blinddarmdilatation

    OpenAIRE

    Beckmann, C

    2011-01-01

    In der vorliegenden Dissertation werden die klinischen Befunde, die Laborbe-funde, die Therapie und der Krankheitsverlauf von 461 Kühen mit Blinddarmdila-tation, -torsion und -retroflexion beschrieben, die vom 25. Juni 1997 bis zum 24. Juni 2008 im Departement für Nutztiere der Vetsuisse-Fakultät Zürich behan-delt wurden. 246 Kühe (53.4 %) wiesen eine Blinddarmdilatation, 142 Kühe (30.8 %) eine Blinddarmdilatation und -retroflexion und 73 Kühe (15.8 %) eine Blinddarmdilatation und -torsion au...

  2. Herstellung und Charakterisierung von Funktionsschichten mit kombinierter Schutz- und Sensoreigenschaft

    OpenAIRE

    Brunken, Hayo

    2013-01-01

    Im Mittelpunkt der vorliegenden Arbeit stand die Entwicklung neuer ferromagnetischer Schutzschichten für Hochtemperatur-Sensorsysteme. Hierbei war es das Ziel, eine fernabfragbare Messung der Temperatur und des Verspannungszustandes der Schicht zu ermöglichen. Hierzu wurden dünne FeCo/AlN-, Fe/B- sowie FeCo/Ti- Precursorschichten abgeschieden und anschließend wärmebehandelt, mit dem Ziel der Ausbildung gewünschter funktionaler Phasen. Die Analyse der Materialsysteme zeigte, das...

  3. Effiziente hochauflösende Röntgenemissionsspektrometrie mit Synchrotronstrahlung

    OpenAIRE

    Unterumsberger, Rainer

    2015-01-01

    Das Ziel der vorliegenden Arbeit bestand darin, durch die Erhöhung der Sensitivität eines wellenlängendispersiven Spektrometers (WDS) im Spektralbereich weicher Röntgenstrahlung Zugang zu hochauflösender Röntgenemissionsspetrometrie an nanoskaligen Materialien leichter Elemente und Übergangsmetallen zu erhalten. Die Erhöhung der Sensitivität wurde durch eine Refokussierung der anregenden Undulatorstrahlung erreicht. Mit der erhöhten Sensitivität des WDS konnten zum einen die chemischen Spezie...

  4. Laser Microbial Killing and Biofilm Disruption

    Science.gov (United States)

    Krespi, Yosef P.; Kizhner, Victor

    2009-06-01

    Objectives: To analyze the ability of NIR lasers to reduce bacterial load and demonstrate the capability of fiber-based Q-switched Nd:YAG laser disrupting biofilm. Study Design: NIR diode laser was tested in vitro and in vivo using pathogenic microorganisms (S. aureus, S. pneumoniae, P. aeruginosa). In addition biofilms were grown from clinical Pseudomonas isolates and placed in culture plates, screws, tympanostomy tubes and PET sutures. Methods: In the animal experiments acute rhinosinusitis model was created by packing the rabbit nose with bacteria soaked solution. The nasal pack was removed in two days and nose was exposed to laser irradiation. A 940 nm diode laser with fiber diffuser was used. Nasal cultures were obtained before and after the laser treatments. Animals were sacrificed fifteen days following laser treatment and bacteriologic/histologic results analyzed. Q-switched Nd:YAG laser generated shockwave pulses were delivered on biofilm using special probes over culture plates, screws, tubes, and PET sutures for the biofilm experiments. Results: Average of two log bacteria reduction was achieved with NIR laser compared to controls. Histologic studies demonstrated preservation of tissue integrity without significant damage to mucosa. Biofilms were imaged before, during and after treatment using a confocal microscope. During laser-generated shockwave application, biofilm was initially seen to oscillate and eventually break off. Large and small pieces of biofilm were totally and instantly removed from the surface to which they were attached in seconds. Conclusions: Significant bacterial reduction was achieved with NIR laser therapy in this experimental in vitro and animal study. In addition we disrupted Pseudomonas aeruginosa biofilms using Q-switched Nd:YAG laser and special probes generating plasma and shockwave. This new and innovative method of bacteria killing and biofilm disruption without injuring host tissue may have clinical application in the

  5. Implications of Biofilm Formation on Urological Devices

    Science.gov (United States)

    Cadieux, Peter A.; Wignall, Geoffrey R.; Carriveau, Rupp; Denstedt, John D.

    2008-09-01

    Despite millions of dollars and several decades of research targeted at their prevention and eradication, biofilm-associated infections remain the major cause of urological device failure. Numerous strategies have been aimed at improving device design, biomaterial composition, surface properties and drug delivery, but have been largely circumvented by microbes and their plethora of attachment, host evasion, antimicrobial resistance, and dissemination strategies. This is not entirely surprising since natural biofilm formation has been going on for millions of years and remains a major part of microorganism survival and evolution. Thus, the fact that biofilms develop on and in the biomaterials and tissues of humans is really an extension of this natural tendency and greatly explains why they are so difficult for us to combat. Firstly, biofilm structure and composition inherently provide a protective environment for microorganisms, shielding them from the shear stress of urine flow, immune cell attack and some antimicrobials. Secondly, many biofilm organisms enter a metabolically dormant state that renders them tolerant to those antibiotics and host factors able to penetrate the biofilm matrix. Lastly, the majority of organisms that cause biofilm-associated urinary tract infections originate from our own oral cavity, skin, gastrointestinal and urogenital tracts and therefore have already adapted to many of our host defenses. Ultimately, while biofilms continue to hold an advantage with respect to recurrent infections and biomaterial usage within the urinary tract, significant progress has been made in understanding these dynamic microbial communities and novel approaches offer promise for their prevention and eradication. These include novel device designs, antimicrobials, anti-adhesive coatings, biodegradable polymers and biofilm-disrupting compounds and therapies.

  6. Diagnostic of Fungal Infections Related to Biofilms.

    Science.gov (United States)

    Sanguinetti, Maurizio; Posteraro, Brunella

    2016-01-01

    Fungal biofilm-related infections, most notably those caused by the Candida and Aspergillus genera, need to be diagnosed accurately and rapidly to avoid often unfavorable outcomes. Despite diagnosis of these infections is still based on the traditional histopathology and culture, the use of newer, rapid methods has enormously enhanced the diagnostic capability of a modern clinical mycology laboratory. Thus, while accurate species-level identification of fungal isolates can be achieved with turnaround times considerably shortened, nucleic acid-based or antigen-based detection methods can be considered useful adjuncts for the diagnosis of invasive forms of candidiasis and aspergillosis. Furthermore, simple, reproducible, and fast methods have been developed to quantify biofilm production by fungal isolates in vitro. In this end, isolates can be categorized as low, moderate, or high biofilm-forming, and this categorization may reflect their differential response to the conventional antifungal therapy. By means of drug susceptibility testing performed on fungal biofilm-growing isolates, it is now possible to evaluate not only the activity of conventional antifungal agents, but also of novel anti-biofilm agents. Despite this, future diagnostic methods need to target specific biofilm components/molecules, in order to provide a direct proof of the presence of this growth phenotype on the site of infection. In the meantime, our knowledge of the processes underlying the adaptive drug resistance within the biofilm has put into evidence biofilm-specific molecules that could be potentially helpful as therapeutic targets. Surely, the successful management of clinically relevant fungal biofilms will rely upon the advancement and/or refinement of these approaches. PMID:27300347

  7. Prevention of biofilm formation and removal of existing biofilms by extracellular DNases of Campylobacter jejuni.

    Directory of Open Access Journals (Sweden)

    Helen L Brown

    Full Text Available The fastidious nature of the foodborne bacterial pathogen Campylobacter jejuni contrasts with its ability to survive in the food chain. The formation of biofilms, or the integration into existing biofilms by C. jejuni, is thought to contribute to food chain survival. As extracellular DNA (eDNA has previously been proposed to play a role in C. jejuni biofilms, we have investigated the role of extracellular DNases (eDNases produced by C. jejuni in biofilm formation. A search of 2791 C. jejuni genomes highlighted that almost half of C. jejuni genomes contains at least one eDNase gene, but only a minority of isolates contains two or three of these eDNase genes, such as C. jejuni strain RM1221 which contains the cje0256, cje0566 and cje1441 eDNase genes. Strain RM1221 did not form biofilms, whereas the eDNase-negative strains NCTC 11168 and 81116 did. Incubation of pre-formed biofilms of NCTC 11168 with live C. jejuni RM1221 or with spent medium from a RM1221 culture resulted in removal of the biofilm. Inactivation of the cje1441 eDNase gene in strain RM1221 restored biofilm formation, and made the mutant unable to degrade biofilms of strain NCTC 11168. Finally, C. jejuni strain RM1221 was able to degrade genomic DNA from C. jejuni NCTC 11168, 81116 and RM1221, whereas strain NCTC 11168 and the RM1221 cje1441 mutant were unable to do so. This was mirrored by an absence of eDNA in overnight cultures of C. jejuni RM1221. This suggests that the activity of eDNases in C. jejuni affects biofilm formation and is not conducive to a biofilm lifestyle. These eDNases do however have a potential role in controlling biofilm formation by C. jejuni strains in food chain relevant environments.

  8. A novel planar flow cell for studies of biofilm heterogeneity and flow-biofilm interactions

    OpenAIRE

    Zhang, Wei; Sileika, Tadas S.; Chen, Cheng; Liu, Yang; Lee, Jisun; Packman, Aaron I.

    2011-01-01

    Biofilms are microbial communities growing on surfaces, and are ubiquitous in nature, in bioreactors, and in human infection. Coupling between physical, chemical, and biological processes is known to regulate the development of biofilms; however, current experimental systems do not provide sufficient control of environmental conditions to enable detailed investigations of these complex interactions. We developed a novel planar flow cell that supports biofilm growth under complex two-dimension...

  9. Prevention of biofilm formation and removal of existing biofilms by extracellular DNases of Campylobacter jejuni.

    Science.gov (United States)

    Brown, Helen L; Reuter, Mark; Hanman, Kate; Betts, Roy P; van Vliet, Arnoud H M

    2015-01-01

    The fastidious nature of the foodborne bacterial pathogen Campylobacter jejuni contrasts with its ability to survive in the food chain. The formation of biofilms, or the integration into existing biofilms by C. jejuni, is thought to contribute to food chain survival. As extracellular DNA (eDNA) has previously been proposed to play a role in C. jejuni biofilms, we have investigated the role of extracellular DNases (eDNases) produced by C. jejuni in biofilm formation. A search of 2791 C. jejuni genomes highlighted that almost half of C. jejuni genomes contains at least one eDNase gene, but only a minority of isolates contains two or three of these eDNase genes, such as C. jejuni strain RM1221 which contains the cje0256, cje0566 and cje1441 eDNase genes. Strain RM1221 did not form biofilms, whereas the eDNase-negative strains NCTC 11168 and 81116 did. Incubation of pre-formed biofilms of NCTC 11168 with live C. jejuni RM1221 or with spent medium from a RM1221 culture resulted in removal of the biofilm. Inactivation of the cje1441 eDNase gene in strain RM1221 restored biofilm formation, and made the mutant unable to degrade biofilms of strain NCTC 11168. Finally, C. jejuni strain RM1221 was able to degrade genomic DNA from C. jejuni NCTC 11168, 81116 and RM1221, whereas strain NCTC 11168 and the RM1221 cje1441 mutant were unable to do so. This was mirrored by an absence of eDNA in overnight cultures of C. jejuni RM1221. This suggests that the activity of eDNases in C. jejuni affects biofilm formation and is not conducive to a biofilm lifestyle. These eDNases do however have a potential role in controlling biofilm formation by C. jejuni strains in food chain relevant environments.

  10. Ecology of Anti-Biofilm Agents II: Bacteriophage Exploitation and Biocontrol of Biofilm Bacteria

    OpenAIRE

    Abedon, Stephen T.

    2015-01-01

    Bacteriophages are the viruses of bacteria. In the guise of phage therapy they have been used for decades to successfully treat what are probable biofilm-containing chronic bacterial infections. More recently, phage treatment or biocontrol of biofilm bacteria has been brought back to the laboratory for more rigorous assessment as well as towards the use of phages to combat environmental biofilms, ones other than those directly associated with bacterial infections. Considered in a companion ar...

  11. A novel approach for harnessing biofilm communities in moving bed biofilm reactors for industrial wastewater treatment

    OpenAIRE

    Lemire, Joe A.; Marc A Demeter; Iain George; Howard Ceri; Turner, Raymond J.

    2015-01-01

    Moving bed biofilm reactors (MBBRs) are an effective biotechnology for treating industrial wastewater. Biomass retention on moving bed biofilm reactor (MBBR) carriers (biofilm support materials), allows for the ease-of-operation and high treatment capacity of MBBR systems. Optimization of MBBR systems has largely focused on aspects of carrier design, while little attention has been paid to enhancing strategies for harnessing microbial biomass. Previously, our research group demonstrated that ...

  12. Gene Transfer Efficiency in Gonococcal Biofilms: Role of Biofilm Age, Architecture, and Pilin Antigenic Variation

    OpenAIRE

    Kouzel, Nadzeya; Oldewurtel, Enno R.; Maier, Berenike

    2015-01-01

    Extracellular DNA is an important structural component of many bacterial biofilms. It is unknown, however, to which extent external DNA is used to transfer genes by means of transformation. Here, we quantified the acquisition of multidrug resistance and visualized its spread under selective and nonselective conditions in biofilms formed by Neisseria gonorrhoeae. The density and architecture of the biofilms were controlled by microstructuring the substratum for bacterial adhesion. Horizontal t...

  13. Quorum sensing inhibitors disable bacterial biofilms

    DEFF Research Database (Denmark)

    Bjarnsholt, Thomas; Tolker-Nielsen, Tim; Givskov, Michael

    2011-01-01

    It is now evident that bacteria assume the biofilm mode of growth during chronic infections. The important hallmarks of biofilm infections are development of local inflammations, extreme tolerance to the action of conventional antimicrobial agents and an almost infinite capacity to evade the host...... defence systems in particular innate immunity. In the biofilm mode, bacteria use cell to cell communication termed quorum-sensing (QS) to coordinate expression of virulence, tolerance towards a number of antimicrobial agents and shielding against the host defence system. Chemical biology approaches may...

  14. Cellular chain formation in Escherichia coli biofilms

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk; Klemm, Per

    2009-01-01

    In this study we report on a novel structural phenotype in Escherichia coli biofilms: cellular chain formation. Biofilm chaining in E. coli K-12 was found to occur primarily by clonal expansion, but was not due to filamentous growth. Rather, chain formation was the result of intercellular......; type I fimbriae expression significantly reduced cellular chain formation, presumably by steric hindrance. Cellular chain formation did not appear to be specific to E coli K-12. Although many urinary tract infection (UTI) isolates were found to form rather homogeneous, flat biofilms, three isolates...

  15. Biofilm formation in a hot water system

    DEFF Research Database (Denmark)

    Bagh, L.K.; Albrechtsen, Hans-Jørgen; Arvin, Erik;

    2002-01-01

    The biofilm formation rate was measured in situ in a hot water system in an apartment building by specially designed sampling equipment, and the net growth of the suspended bacteria was measured by incubation of water samples with the indigeneous bacteria. The biofilm formation rate reached......, in the sludge, or in the water from the distribution system was negligible. This indicated that bacterial growth took place on the inner surfaces in the hot water system and biofilm formation and detachment of bacteria could account for most of the suspended bacteria actually measured in hot water. Therefore...

  16. Anaerobic granular sludge and biofilm reactors

    DEFF Research Database (Denmark)

    Skiadas, Ioannis V.; Gavala, Hariklia N.; Schmidt, Jens Ejbye;

    2003-01-01

    by the immobilization of the biomass, which forms static biofilms, particle-supported biofilms, or granules depending on the reactor's operational conditions. The advantages of the high-rate anaerobic digestion over the conventional aerobic wastewater treatment methods has created a clear trend for the change......-rate anaerobic treatment systems based on anaerobic granular sludge and biofilm are described in this chapter. Emphasis is given to a) the Up-flow Anaerobic Sludge Blanket (UASB) systems, b) the main characteristics of the anaerobic granular sludge, and c) the factors that control the granulation process...

  17. A personal history of research on microbial biofilms and biofilm infections.

    Science.gov (United States)

    Høiby, Niels

    2014-04-01

    The observation of aggregated microorganisms surrounded by a self-produced matrix adhering to surfaces or located in tissues or secretions is as old as microbiology, with both Leeuwenhoek and Pasteur describing the phenomenon. In environmental and technical microbiology, biofilms were already shown 80-90 years ago to be important for biofouling on submerged surfaces, e.g. ships. The concept of biofilm infections and their importance in medicine is, however, biofilm was introduced into medicine in 1985 by Costerton. In the following decades, it became obvious that biofilm infections are widespread in medicine, and their importance is now generally accepted.

  18. Successional development of biofilms in moving bed biofilm reactor (MBBR) systems treating municipal wastewater.

    Science.gov (United States)

    Biswas, Kristi; Taylor, Michael W; Turner, Susan J

    2014-02-01

    Biofilm-based technologies, such as moving bed biofilm reactor (MBBR) systems, are widely used to treat wastewater. Biofilm development is important for MBBR systems as much of the microbial biomass is retained within reactors as biofilm on suspended carriers. Little is known about this process of biofilm development and the microorganisms upon which MBBRs rely. We documented successional changes in microbial communities as biofilms established in two full-scale MBBR systems treating municipal wastewater over two seasons. 16S rRNA gene-targeted pyrosequencing and clone libraries were used to describe microbial communities. These data indicate a successional process that commences with the establishment of an aerobic community dominated by Gammaproteobacteria (up to 52 % of sequences). Over time, this community shifts towards dominance by putatively anaerobic organisms including Deltaproteobacteria and Clostridiales. Significant differences were observed between the two wastewater treatment plants (WWTPs), mostly due to a large number of sequences (up to 55 %) representing Epsilonproteobacteria (mostly Arcobacter) at one site. Archaea in young biofilms included several lineages of Euryarchaeota and Crenarchaeota. In contrast, the mature biofilm consisted entirely of Methanosarcinaceae (Euryarchaeota). This study provides new insights into the community structure of developing biofilms at full-scale WWTPs and provides the basis for optimizing MBBR start-up and operational parameters.

  19. Ecology of Anti-Biofilm Agents II: Bacteriophage Exploitation and Biocontrol of Biofilm Bacteria

    Directory of Open Access Journals (Sweden)

    Stephen T. Abedon

    2015-09-01

    Full Text Available Bacteriophages are the viruses of bacteria. In the guise of phage therapy they have been used for decades to successfully treat what are probable biofilm-containing chronic bacterial infections. More recently, phage treatment or biocontrol of biofilm bacteria has been brought back to the laboratory for more rigorous assessment as well as towards the use of phages to combat environmental biofilms, ones other than those directly associated with bacterial infections. Considered in a companion article is the inherent ecological utility of bacteriophages versus antibiotics as anti-biofilm agents. Discussed here is a model for phage ecological interaction with bacteria as they may occur across biofilm-containing ecosystems. Specifically, to the extent that individual bacterial types are not highly abundant within biofilm-containing environments, then phage exploitation of those bacteria may represent a “Feast-or-famine” existence in which infection of highly localized concentrations of phage-sensitive bacteria alternate with treacherous searches by the resulting phage progeny virions for new concentrations of phage-sensitive bacteria to infect. An updated synopsis of the literature concerning laboratory testing of phage use to combat bacterial biofilms is then provided along with tips on how “Ecologically” such phage-mediated biofilm control can be modified to more reliably achieve anti-biofilm efficacy.

  20. Fungal Biofilms: In Vivo Models for Discovery of Anti-Biofilm Drugs.

    Science.gov (United States)

    Nett, Jeniel E; Andes, David R

    2015-06-01

    During infection, fungi frequently transition to a biofilm lifestyle, proliferating as communities of surface-adherent aggregates of cells. Phenotypically, cells in a biofilm are distinct from free-floating cells. Their high tolerance of antifungals and ability to withstand host defenses are two characteristics that foster resilience. Biofilm infections are particularly difficult to eradicate, and most available antifungals have minimal activity. Therefore, the discovery of novel compounds and innovative strategies to treat fungal biofilms is of great interest. Although many fungi have been observed to form biofilms, the most well-studied is Candida albicans. Animal models have been developed to simulate common Candida device-associated infections, including those involving vascular catheters, dentures, urinary catheters, and subcutaneous implants. Models have also reproduced the most common mucosal biofilm infections: oropharyngeal and vaginal candidiasis. These models incorporate the anatomical site, immune components, and fluid dynamics of clinical niches and have been instrumental in the study of drug resistance and investigation of novel therapies. This chapter describes the significance of fungal biofilm infections, the animal models developed for biofilm study, and how these models have contributed to the development of new strategies for the eradication of fungal biofilm infections.

  1. IMPACTS OF BIOFILM FORMATION ON CELLULOSE FERMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    Leschine, Susan

    2009-10-31

    This project addressed four major areas of investigation: i) characterization of formation of Cellulomonas uda biofilms on cellulose; ii) characterization of Clostridium phytofermentans biofilm development; colonization of cellulose and its regulation; iii) characterization of Thermobifida fusca biofilm development; colonization of cellulose and its regulation; and iii) description of the architecture of mature C. uda, C. phytofermentans, and T. fusca biofilms. This research is aimed at advancing understanding of biofilm formation and other complex processes involved in the degradation of the abundant cellulosic biomass, and the biology of the microbes involved. Information obtained from these studies is invaluable in the development of practical applications, such as the single-step bioconversion of cellulose-containing residues to fuels and other bioproducts. Our results have clearly shown that cellulose-decomposing microbes rapidly colonize cellulose and form complex structures typical of biofilms. Furthermore, our observations suggest that, as cells multiply on nutritive surfaces during biofilms formation, dramatic cell morphological changes occur. We speculated that morphological changes, which involve a transition from rod-shaped cells to more rounded forms, might be more apparent in a filamentous microbe. In order to test this hypothesis, we included in our research a study of biofilm formation by T. fusca, a thermophilic cellulolytic actinomycete commonly found in compost. The cellulase system of T. fusca has been extensively detailed through the work of David Wilson and colleagues at Cornell, and also, genome sequence of a T. fusca strain has been determine by the DOE Joint Genome Institute. Thus, T. fusca is an excellent subject for studies of biofilm development and its potential impacts on cellulose degradation. We also completed a study of the chitinase system of C. uda. This work provided essential background information for understanding how C. uda

  2. MIT Lincoln Laboratory: Physics and Technology in the National Interest

    Science.gov (United States)

    Ralston, Richard

    2001-03-01

    This year, MIT is celebrating the 50th anniversary of the founding of Lincoln Laboratory, which was formed at the request of the DoD with the initial goal of developing a national air defense system. In its 50 years, the Laboratory staff have made significant contributions in diverse areas including radar imaging, satellite communications, digital signal processing, computer science, semiconductor materials and solid state physics. The Laboratory has been true to its mission statement, which places strong emphasis on the application of advanced electronics to R&D in the national interest. Much of the technology is transitioned to U.S. industry for both government and commercial use. Annually more than 500 publications and meeting speeches are given, and cooperative developments with industry have targeted technology transitions ranging from next-generation photolithographic tools to microchip lasers. The Laboratory staff have been granted over 400 patents, and license to this intellectual property is at the core of many of the over 70 spin-off companies. MIT employs 2,300 people at Lincoln, including 1,200 professionals with degrees in physics, math, computer science, materials science and the engineering disciplines. Two-fifths of the professional staff are at the doctoral level; over two-thirds hold advanced degrees. This presentation will describe recent examples of research challenges for physicists in a multidisciplinary project-oriented environment.

  3. Behandlungskonzepte für Patienten mit malignen Gliomen

    Directory of Open Access Journals (Sweden)

    Oberndorfer S

    2009-01-01

    Full Text Available In der Behandlung von Patienten mit malignen Gliomen hat sich in den vergangenen Jahren die Standardtherapie der konkomitanten Radiochemotherapie nach dem so genannten „Stupp-Protokoll“ etabliert. Im Falle eines Nichtansprechens oder einer Tumorprogression ist die Therapieentscheidung nach wie vor nicht einheitlich und wird von Zentrum zu Zentrum unterschiedlich gehandhabt. Neue molekularbiologische und neuroradiologische Techniken zeigen zunehmend die Heterogenität dieser Tumoren auf und erklären auch teilweise das unterschiedliche Ansprechen auf verschiedene Therapieansätze. Patienten mit gleicher histologischer Diagnose zeigen unterschiedlichste genetische Veränderungen und unterschiedliches Wachstumsverhalten. Ziel zukünftiger Entwicklungen wird es sein, entsprechend den individuellen Eigenschaften der malignen Gliome auch individuelle Therapiekonzepte zu entwickeln. Vielversprechend scheint hier für die nähere Zukunft die Kombination von so genannten zielgerichteten Therapien und klassischen Chemotherapien wie Alkylantien. Um eine optimale Betreuung dieser Patienten zu gewährleisten, ist ein neuroonkologisches Tumor-Board mittlerweile internationaler Standard.

  4. MIT nuclear reactor laboratory high school teaching program

    International Nuclear Information System (INIS)

    For the last 6 years, the Massachusetts Institute of Technology (MIT) Nuclear Reactor Laboratory's academic and scientific staffa have been conducting evening seminars for precollege science teachers, parents, and high school students from the New England area. These seminars, as outlined in this paper, are intended to give general information on nuclear technologies with specific emphasis on radiation physics, nuclear medicine, nuclear chemistry, and ongoing research activities at the MIT research reactor. The ultimate goal is to create interest or build on the already existing interest in science and technology by, for example, special student projects. Several small projects have already been completed ranging from environmental research to biological reactions with direct student involvement. Another outcome of these seminars was the change in attitudes of science teachers toward nuclear technology. Numerous letters have been received from the teachers and parents stating their previous lack of knowledge on the beneficial aspects of nuclear technologies and the subsequent inclusion of programs in their curriculum for educating students so that they may also develop a more positive attitude toward nuclear power

  5. Characterization of starvation-induced dispersion in Pseudomonas putida biofilms

    DEFF Research Database (Denmark)

    Gjermansen, Morten; Ragas, Paula Cornelia; Sternberg, Claus;

    2005-01-01

    The biofilm lifestyle, where microbial cells are aggregated because of expression of cell-to-cell interconnecting compounds, is believed to be of paramount importance to microbes in the environment. Because microbes must be able to alternate between sessile and planktonic states, it is anticipated...... that they must be able to regulate their ability to form biofilm and to dissolve biofilm. We present an investigation of a biofilm dissolution process occurring in flow-chamber-grown Pseudomonas putida biofilms. Local starvation-induced biofilm dissolution appears to be an integrated part of P. putida biofilm...... development that causes characteristic structural rearrangements. Rapid global dissolution of entire P. putida biofilms was shown to occur in response to carbon starvation. Genetic analysis suggested that the adjacent P. putida genes PP0164 and PP0165 play a role in P. putida biofilm formation and dissolution...

  6. Treatment planning with functional MRI; Strahlentherapieplanung mit der funktionellen MRT

    Energy Technology Data Exchange (ETDEWEB)

    Georg, P. [EBG MedAustron GmbH, Wiener Neustadt (Austria); Medizinische Universitaet Wien, Christian Doppler Labor fuer die Medizinische Strahlenforschung, Wien (Austria); Andrzejewski, P.; Georg, D. [Medizinische Universitaet Wien, Christian Doppler Labor fuer die Medizinische Strahlenforschung, Wien (Austria); Medizinische Universitaet Wien, Abteilung fuer medizinische Strahlenphysik, Univ. Klinik fuer Strahlentherapie, Wien (Austria); Pinker, K. [Medizinische Universitaet Wien, Christian Doppler Labor fuer die Medizinische Strahlenforschung, Wien (Austria); Medizinische Universitaet Wien, Abteilung fuer molekulare Bildgebung, Univ. Klinik fuer Radiologie und Nuklearmedizin, Wien (Austria)

    2015-12-15

    The aim of magnetic resonance imaging (MRI) guided radiotherapy is high precision in treatment delivery. With new developments it is possible to focus the high dose irradiation on the tumor while sparing the surrounding tissue. The achievements in precision of the treatment planning and delivery warrant equally precise tumor definition. In conventional radiation therapy it is necessary to carry out a planning computed tomography (CT). For many tumors there is also need for an additional morphological MRI because of more accurate tumor definition. In standard radiotherapy the tumor volume is irradiated with a homogeneous dose. The aim of functional multiparametric MRI is to visualize and quantify biological, physiological and pathological processes at the cellular and molecular levels. Based on this information it is possible to elucidate tumor biology and identify subvolumes of more aggressive behavior. They are often radiotherapy-resistant, leading to tumor recurrence thus requiring further dose escalation. The concept of inhomogeneous tumor irradiation according to its biological behavior is called dose painting. Dose painting is technically feasible. The expected clinical benefit is motivated by selective treatment adaptations based on biological tumor characteristics. Tumors show variable response to therapy underlining the need for individual treatment plans. This approach may lead not only to higher local control but also to better sparing of normal surrounding tissue. With the clinical implementation of dose painting, improvements in the therapeutic outcome can be expected. Due to the existing technical challenges, extensive collaboration between radiation oncologists, radiologists, medical physicists and radiation biologists is needed. (orig.) [German] Die Strahlentherapieplanung mit der funktionellen Magnetresonanztomographie (fMRT) zielt auf eine Hochpraezisionsradiotherapie ab. Mit den modernen Technologien ist es moeglich, die Strahlentherapie nahezu

  7. Susceptibility of Porphyromonas gingivalis in biofilms to amoxicillin, doxycycline and metronidazole

    DEFF Research Database (Denmark)

    Larsen, T.

    2002-01-01

    Biofilm, Porphyromonas gingivalis, susceptibility testing, amoxicillin, doxycycline, metronidazole......Biofilm, Porphyromonas gingivalis, susceptibility testing, amoxicillin, doxycycline, metronidazole...

  8. Bacterial adhesion and biofilms on surfaces

    Institute of Scientific and Technical Information of China (English)

    Trevor Roger Garrett; Manmohan Bhakoo; Zhibing Zhang

    2008-01-01

    Bacterial adhesion has become a significant problem in industry and in the domicile,and much research has been done for deeper understanding of the processes involved.A generic biological model of bacterial adhesion and population growth called the bacterial biofilm growth cycle,has been described and modified many times.The biofilm growth cycle encompasses bacterial adhesion at all levels,starting with the initial physical attraction of bacteria to a substrate,and ending with the eventual liberation of cell dusters from the biofilm matrix.When describing bacterial adhesion one is simply describing one or more stages of biofilm development,neglecting the fact that the population may not reach maturity.This article provides an overview of bacterial adhesion.cites examples of how bac-terial adhesion affects industry and summarises methods and instrumentation used to improve our understanding of the adhesive prop-erties of bacteria.

  9. Bursting the bubble on bacterial biofilms

    DEFF Research Database (Denmark)

    Crusz, Shanika A; Popat, Roman; Rybtke, Morten Theil;

    2012-01-01

    The flow cell biofilm system is an important and widely used tool for the in vitro cultivation and evaluation of bacterial biofilms under hydrodynamic conditions of flow. This paper provides an introduction to the background and use of such systems, accompanied by a detailed guide to the assembly...... of the apparatus including the description of new modifications which enhance its performance. As such, this is an essential guide for the novice biofilm researcher as well as providing valuable trouble-shooting techniques for even the most experienced laboratories. The adoption of a common and reliable...... methodology amongst researchers would enable findings to be shared and replicated amongst the biofilm research community, with the overall aim of advancing understanding and management of these complex and widespread bacterial communities....

  10. Synergistic effects in mixed Escherichia coli biofilms

    DEFF Research Database (Denmark)

    Reisner, A.; Holler, B.M.; Molin, Søren;

    2006-01-01

    the pathways governing development of more complex heterogeneous communities. In this study, we established a laboratory model where biofilm-stimulating effects due to interactions between genetically diverse strains of Escherichia coli were monitored. Synergistic induction of biofilm formation resulting from...... the cocultivation of 403 undomesticated E. coli strains with a characterized E. coli K-12 strain was detected at a significant frequency. The survey suggests that different mechanisms underlie the observed stimulation, yet synergistic development of biofilm within the subset of E. coli isolates (n = 56) exhibiting...... the strongest effects was most often linked to conjugative transmission of natural plasmids carried by the E. coli isolates (70%). Thus, the capacity of an isolate to promote the biofilm through cocultivation was (i) transferable to the K-12 strain, (ii) was linked with the acquisition of conjugation genes...

  11. Glycopeptide dendrimers as Pseudomonas aeruginosa biofilm inhibitors.

    Science.gov (United States)

    Reymond, Jean-Louis; Bergmann, Myriam; Darbre, Tamis

    2013-06-01

    Synthetic glycopeptide dendrimers composed of a branched oligopeptide tree structure appended with glycosidic groups at its multiple N-termini were investigated for binding to the Pseudomonas aeruginosa lectins LecB and LecA. These lectins are partly responsible for the formation of antibiotic resistant biofilms in the human pathogenic bacterium P. aeruginosa, which causes lethal airway infections in immune-compromised and cystic fibrosis patients. Glycopeptide dendrimers with high affinity to the lectins were identified by screening of combinatorial libraries. Several of these dendrimers, in particular the LecB specific glycopeptide dendrimers FD2 and D-FD2 and the LecA specific glycopeptide dendrimers GalAG2 and GalBG2, also efficiently block P. aeruginosa biofilm formation and induce biofilm dispersal in vitro. Structure-activity relationship and structural studies are reviewed, in particular the observation that multivalency is essential to the anti-biofilm effect in these dendrimers.

  12. Controlling the oral biofilm with antimicrobials.

    Science.gov (United States)

    Marsh, P D

    2010-06-01

    The aim of this article is to review the properties of compounds available for the control of dental plaque biofilms, and describe their mode of action. The mouth is colonised by a diverse but characteristic collection of micro-organisms, which confer benefit to host. Numerous antiplaque (e.g. surfactants, essential oils) and antimicrobial agents (e.g. bisbiguanides, metal ions, phenols, quaternary ammonium compounds, etc.) have been successfully formulated into toothpastes and mouthrinses to control plaque biofilms. At high concentrations, these agents can remove biofilm and/or kill disease-associated bacteria, while even at sub-lethal levels they can inhibit the expression of pathogenic traits. Successful antimicrobial agents are able to meet the apparently contradictory requirements of maintaining the oral biofilm at levels compatible with oral health but without disrupting the natural and beneficial properties of the resident oral microflora.

  13. Understanding, preventing and eradicating Klebsiella pneumoniae biofilms.

    Science.gov (United States)

    Ribeiro, Suzana Meira; Cardoso, Marlon Henrique; Cândido, Elizabete de Souza; Franco, Octávio Luiz

    2016-01-01

    The ability of pathogenic bacteria to aggregate and form biofilm represents a great problem for public health, since they present extracellular components that encase these micro-organisms, making them more resistant to antibiotics and host immune attack. This may become worse when antibiotic-resistant bacterial strains form biofilms. However, antibiofilm screens with different compounds may reveal potential therapies to prevent/treat biofilm infections. Here, we focused on Klebsiella pneumoniae, an opportunistic bacterium that causes different types of infections, including in the bloodstream, meninges, lungs, urinary system and at surgical sites. We also highlight aspects involved in the formation and maintenance of K. pneumoniae biofilms, as well as resistance and the emergence of new trends to combat this health challenge. PMID:27064296

  14. Treatment of Oral Multispecies Biofilms by an Anti-Biofilm Peptide.

    Science.gov (United States)

    Wang, Zhejun; de la Fuente-Núñez, Cesar; Shen, Ya; Haapasalo, Markus; Hancock, Robert E W

    2015-01-01

    Human oral biofilms are multispecies microbial communities that exhibit high resistance to antimicrobial agents. Dental plaque gives rise to highly prevalent and costly biofilm-related oral infections, which lead to caries or other types of oral infections. We investigated the ability of the recently identified anti-biofilm peptide 1018 to induce killing of bacterial cells present within oral multispecies biofilms. At 10 μg/ml (6.5 μM), peptide 1018 was able to significantly (pbiofilm formation over 3 days. The activity of the peptide on preformed biofilms was found to be concentration-dependent since more than 60% of the total plaque biofilm cell population was killed by 10 μg/ml of peptide 1018 in 3 days, while at 5 μg/ml 50% of cells were dead and at 1 μg/ml the peptide triggered cell death in around 30% of the total bacterial population, as revealed by confocal microscopy. The presence of saliva did not affect peptide activity, since no statistically significant difference was found in the ability of peptide 1018 to kill oral biofilms using either saliva coated and non-saliva coated hydroxyapatite surfaces. Scanning electron microscopy experiments indicated that peptide 1018 induced cell lysis in plaque biofilms. Furthermore, combined treatment using peptide 1018 and chlorhexidine (CHX) increased the anti-biofilm activity of each compound compared to when these were used alone, resulting in >50% of the biofilm being killed and >35% being dispersed in only 3 minutes. Peptide 1018 may potentially be used by itself or in combination with CHX as a non-toxic and effective anti-biofilm agent for plaque disinfection in clinical dentistry.

  15. Prospects for Anti-Biofilm Pharmaceuticals

    OpenAIRE

    Stewart, Philip S.

    2015-01-01

    This commentary highlights several avenues currently being pursued in research labs to the development of new anti-biofilm pharmaceuticals. There is a real need for alternative therapeutic modalities for treating the persistent infections that sometimes form on implanted medical devices or compromised niches within the body. Strategies being researched include discovering new antimicrobial agents that kill microorganisms in biofilms more effectively than do existing antibiotics, designing dru...

  16. Crenarchaeal Biofilm Formation under Extreme Conditions

    OpenAIRE

    Andrea Koerdt; Julia Gödeke; Jürgen Berger; Thormann, Kai M.; Sonja-Verena Albers

    2010-01-01

    BACKGROUND: Biofilm formation has been studied in much detail for a variety of bacterial species, as it plays a major role in the pathogenicity of bacteria. However, only limited information is available for the development of archaeal communities that are frequently found in many natural environments. METHODOLOGY: We have analyzed biofilm formation in three closely related hyperthermophilic crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus and S. tokodaii. We established a microtitr...

  17. Vulnerability of Pathogenic Biofilms to Micavibrio aeruginosavorus▿

    OpenAIRE

    Kadouri, Daniel; Venzon, Nel C.; O'Toole, George A

    2006-01-01

    The host specificity of the gram-negative exoparasitic predatory bacterium Micavibrio aeruginosavorus was examined. M. aeruginosavorus preyed on Pseudomonas aeruginosa, as previously reported, as well as Burkholderia cepacia, Klebsiella pneumoniae, and numerous clinical isolates of these species. In a static assay, a reduction in biofilm biomass was observed as early as 3 hours after exposure to M. aeruginosavorus, and an ∼100-fold reduction in biofilm cell viability was detected following a ...

  18. Desiccation stress in two intertidal beachrock biofilms

    OpenAIRE

    Petrou, Katherina; Trimborn, Scarlett; Kühl, Michael; Ralph, Peter J.

    2014-01-01

    Chlorophyll a fluorescence was used to look at the effect of desiccation on the photophysiology in two beachrock microbial biofilms from the intertidal rock platform of Heron Island, Australia. The photophysiological response to desiccation differed between the beachrock microbial communities. The black biofilm from the upper shoreline, dominated by Calothrix sp., showed a response typical of desiccation-tolerant cyanobacteria, where photosynthesis closed down during air exposure with a rapid...

  19. DIFFUSION IN BIOFILMS RESPIRING ON ELECTRODES

    OpenAIRE

    Renslow, RS; Babauta, JT; Majors, PD; Beyenal, H

    2012-01-01

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed noninvasive, nondestr...

  20. Uranium Immobilization by Sulfate-reducing Biofilms

    International Nuclear Information System (INIS)

    Hexavalent uranium [U(VI)] was immobilized using biofilms of the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans G20. The biofilms were grown in flat-plate continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. U(VI) was continuously fed into the reactor for 32 weeks at a concentration of 126 ?M. During this time, the soluble U(VI) was removed (between 88 and 96% of feed) from solution and immobilized in the biofilms. The dynamics of U immobilization in the sulfate-reducing biofilms were quantified by estimating: (1) microbial activity in the SRB biofilm, defined as the hydrogen sulfide (H2S) production rate and estimated from the H2S concentration profiles measured using microelectrodes across the biofilms; (2) concentration of dissolved U in the solution; and (3) the mass of U precipitated in the biofilm. Results suggest that U was immobilized in the biofilms as a result of two processes: (1) enzymatically and (2) chemically, by reacting with microbially generated H2S. Visual inspection showed that the dissolved sulfide species reacted with U(VI) to produce a black precipitate. Synchrotron-based U L3-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of U precipitated abiotically by sodium sulfide indicated that U(VI) had been reduced to U(IV). Selected-area electron diffraction pattern and crystallographic analysis of transmission electron microscope lattice-fringe images confirmed the structure of precipitated U as being that of uraninite

  1. Physicochemical characteristics and microbial community evolution of biofilms during the start-up period in a moving bed biofilm reactor.

    Science.gov (United States)

    Zhu, Yan; Zhang, Yan; Ren, Hong-Qiang; Geng, Jin-Ju; Xu, Ke; Huang, Hui; Ding, Li-Li

    2015-03-01

    This study aimed to investigate biofilm properties evolution coupled with different ages during the start-up period in a moving bed biofilm reactor system. Physicochemical characteristics including adhesion force, extracellular polymeric substances (EPS), morphology as well as volatile solid and microbial community were studied. Results showed that the formation and development of biofilms exhibited four stages, including (I) initial attachment and young biofilm formation, (II) biofilms accumulation, (III) biofilm sloughing and updating, and (IV) biofilm maturation. During the whole start-up period, adhesion force was positively and significantly correlated with the contents of EPS, especially the content of polysaccharide. In addition, increased adhesion force and EPS were beneficial for biofilm retention. Gram-negative bacteria mainly including Sphaerotilus, Zoogloea and Haliscomenobacter were predominant in the initial stage. Actinobacteria was beneficial to resist sloughing. Furthermore, filamentous bacteria were dominant in maturation biofilm.

  2. Linking nitrifying biofilm characteristics and nitrification performance in moving-bed biofilm reactors for polluted raw water pretreatment.

    Science.gov (United States)

    Zhang, Shuangfu; Wang, Yayi; He, Weitao; Xing, Meiyan; Wu, Min; Yang, Jian; Gao, Naiyun; Sheng, Guangyao; Yin, Daqiang; Liu, Shanhu

    2013-10-01

    Biofilm physiology was characterized by four biofilm constituents, i.e., polysaccharides, proteins (PN), humic-like substances and phospholipids (PL), for the first time to explore the relationships between biofilm characteristics and nitrification performance in moving-bed biofilm reactors (MBBRs) designed for pretreatment of polluted raw surface water for potable supply. The biofilm compositions depended highly on the balance of microbial decay and nitrification processes. The increased ammonia loading greatly regulated the community structure, promoting the dominance of nitrifiers and their proportions in the nitrifying biofilm. Nitrification rate and activity correlated linearly with the fractions of volatile solids (VS), PN and PL, which were related to nitrification processes in the biofilm. The specific biofilm activity demonstrated an exponential-asymptotic relationship with ratios of PN/VS and PL/VS. Thus, analyzing biofilm characteristics can be valid for estimating nitrification performance in MBBRs, and may offer engineers with basis to optimize MBBR design and operation.

  3. Enhanced Biofilm Formation and Increased Resistance to Antimicrobial Agents and Bacterial Invasion Are Caused by Synergistic Interactions in Multispecies Biofilms

    DEFF Research Database (Denmark)

    Burmølle, Mette; Webb, J.S.; Rao, D.;

    2006-01-01

    Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. However, few reports specifically address interactions within multispecies biofilms. In this study, 17 epiphytic bacterial strains, isolated...... specific interactions. In summary, our data strongly indicate that synergistic effects promote biofilm biomass and resistance of the biofilm to antimicrobial agents and bacterial invasion in multispecies biofilms.......Most biofilms in their natural environments are likely to consist of consortia of species that influence each other in synergistic and antagonistic manners. However, few reports specifically address interactions within multispecies biofilms. In this study, 17 epiphytic bacterial strains, isolated......-species biofilms resisted invasion to a greater extent than did the biofilms formed by the single species. Replacement of each strain by its cell-free culture supernatant suggested that synergy was dependent both on species-specific physical interactions between cells and on extracellular secreted factors or less...

  4. Wirksamkeit der modifizierten Dualtherapie mit Omeprazol und Amoxicillin bei Helicobacter pylori -Infektionen mit Metronidazol- und Clarithromycin-resistenten Stämmen : eine Pilotstudie

    OpenAIRE

    Schröder, Holger

    2002-01-01

    Die Bedeutung einer HP-Gastritis ist bekannt. Therapiestudien haben gezeigt, dass eine prätherapeutische Resistenz von HP gegenüber Metronidazol und/oder Clarithromycin zu einer Minderung der Eradikationsrate von 20-30% bis hin zum Versagen führt. Die Zahl der Patienten mit doppelresistentem HP-Stamm nimmt rasch zu. Dies macht die Suche nach einer alternativen bzw. Reservetherapie erforderlich. 49 Patienten mit kulturell nachgewiesener Doppelresistenz von HP gegen Metronidazol und...

  5. Role of Biofilm Roughness and Hydrodynamic Conditions in Legionella pneumophila Adhesion to and Detachment from Simulated Drinking Water Biofilms

    Science.gov (United States)

    Shen, Yun; Monroy, Guillermo L.; Derlon, Nicolas; Janjaroen, Dao; Huang, Conghui; Morgenroth, Eberhard; Boppart, Stephen A.; Ashbolt, Nicholas J.; Liu, Wen-Tso; Nguyen, Thanh H.

    2015-01-01

    Biofilms in drinking water distribution systems (DWDS) could exacerbate the persistence and associated risks of pathogenic Legionella pneumophila (L. pneumophila), thus raising human health concerns. However, mechanisms controlling adhesion and subsequent detachment of L. pneumophila associated with biofilms remain unclear. We determined the connection between L. pneumophila adhesion and subsequent detachment with biofilm physical structure characterization using optical coherence tomography (OCT) imaging technique. Analysis of the OCT images of multispecies biofilms grown under low nutrient condition up to 34 weeks revealed the lack of biofilm deformation even when these biofilms were exposed to flow velocity of 0.7 m/s, typical flow for DWDS. L. pneumophila adhesion on these biofilm under low flow velocity (0.007 m/s) positively correlated with biofilm roughness due to enlarged biofilm surface area and local flow conditions created by roughness asperities. The preadhered L. pneumophila on selected rough and smooth biofilms were found to detach when these biofilms were subjected to higher flow velocity. At the flow velocity of 0.1 and 0.3 m/s, the ratio of detached cell from the smooth biofilm surface was from 1.3 to 1.4 times higher than that from the rough biofilm surface, presumably because of the low shear stress zones near roughness asperities. This study determined that physical structure and local hydrodynamics control adhesion and detachment from simulated drinking water biofilm, thus it is the first step toward reducing the risk of L. pneumophila exposure and subsequent infections. PMID:25699403

  6. Role of biofilm roughness and hydrodynamic conditions in Legionella pneumophila adhesion to and detachment from simulated drinking water biofilms.

    Science.gov (United States)

    Shen, Yun; Monroy, Guillermo L; Derlon, Nicolas; Janjaroen, Dao; Huang, Conghui; Morgenroth, Eberhard; Boppart, Stephen A; Ashbolt, Nicholas J; Liu, Wen-Tso; Nguyen, Thanh H

    2015-04-01

    Biofilms in drinking water distribution systems (DWDS) could exacerbate the persistence and associated risks of pathogenic Legionella pneumophila (L. pneumophila), thus raising human health concerns. However, mechanisms controlling adhesion and subsequent detachment of L. pneumophila associated with biofilms remain unclear. We determined the connection between L. pneumophila adhesion and subsequent detachment with biofilm physical structure characterization using optical coherence tomography (OCT) imaging technique. Analysis of the OCT images of multispecies biofilms grown under low nutrient condition up to 34 weeks revealed the lack of biofilm deformation even when these biofilms were exposed to flow velocity of 0.7 m/s, typical flow for DWDS. L. pneumophila adhesion on these biofilm under low flow velocity (0.007 m/s) positively correlated with biofilm roughness due to enlarged biofilm surface area and local flow conditions created by roughness asperities. The preadhered L. pneumophila on selected rough and smooth biofilms were found to detach when these biofilms were subjected to higher flow velocity. At the flow velocity of 0.1 and 0.3 m/s, the ratio of detached cell from the smooth biofilm surface was from 1.3 to 1.4 times higher than that from the rough biofilm surface, presumably because of the low shear stress zones near roughness asperities. This study determined that physical structure and local hydrodynamics control L. pneumophila adhesion to and detachment from simulated drinking water biofilm, thus it is the first step toward reducing the risk of L. pneumophila exposure and subsequent infections.

  7. Cholesterin-Interaktion mit G-Protein-gekoppelten Rezeptoren und intrazelluläre Verteilung

    OpenAIRE

    Wiegand, Volker

    2002-01-01

    ZusammenfassungIn dieser Arbeit konnte gezeigt werden, dass neben dem Oxytocinrezeptor auch die anderen Rezeptoren der Familie der Neurohypophysenhormone, die Vasopressinrezeptoren, in der gleichen Weise in ihren Bindungseigenschaften von Cholesterin beeinflusst werden. Im Gegensatz dazu zeigt der Cholecystokininrezeptor Typ B keine direkte Wechselwirkung mit Cholesterin. Durch Austausch der Transmembranhelices 6 und 7 des Oxytocinrezeptors mit entsprechenden Bereichen des Cholecystokininreze...

  8. Dissipative-particle-dynamics model of biofilm growth

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhijie; Meakin, Paul; Tartakovsky, Alexandre M.; Scheibe, Timothy D.

    2011-06-13

    A dissipative particle dynamics (DPD) model for the quantitative simulation of biofilm growth controlled by substrate (nutrient) consumption, advective and diffusive substrate transport, and hydrodynamic interactions with fluid flow (including fragmentation and reattachment) is described. The model was used to simulate biomass growth, decay, and spreading. It predicts how the biofilm morphology depends on flow conditions, biofilm growth kinetics, the rheomechanical properties of the biofilm and adhesion to solid surfaces. The morphology of the model biofilm depends strongly on its rigidity and the magnitude of the body force that drives the fluid over the biofilm.

  9. Fremmedlegemeinfektioner--nyt om biofilm og quorum sensing

    DEFF Research Database (Denmark)

    Høiby, Niels; Johansen, Helle Krogh; Ciofu, Oana;

    2007-01-01

    Biofilms are structured consortia of bacteria embedded in self-produced polymer matrix. Biofilms are resistant to antibiotics, disinfectives and phagocytosis. The persistence of foreign body infections is due to biofilms. Chronic P. aeruginosa lung infection in cystic fibrosis patients is a biofilm....... Bacteria in biofilms communicate by means of quorum sensing which activates genes for virulence factors. Biofilms can be prevented by antibiotic prophylaxis or early therapy or by quorum sensing inhibitors which make them susceptible to antibiotics and phagocytosis. Udgivelsesdato: 2007-Nov-26...

  10. Alginate overproduction affects Pseudomonas aeruginosa biofilm structure and function

    DEFF Research Database (Denmark)

    Hentzer, Morten; Teitzel, G.M.; Balzer, G.J.;

    2001-01-01

    -resistant communities of microorganisms organized in biofilms. Although biofilm formation and the conversion to mucoidy are both important aspects of CF pathogenesis, the relationship between them is at the present unclear. In this study, we report that the overproduction of alginate affects biofilm development...... on an abiotic surface. Biofilms formed by an alginate- overproducing strain exhibit a highly structured architecture and are significantly more resistant to the antibiotic tobramycin than a biofilm formed by an isogenic nonmucoid strain. These results suggest that an important consequence of the conversion...... to mucoidy is an altered biofilm architecture that shows increasing resistance to antimicrobial treatments....

  11. The Host’s Reply to Candida Biofilm

    Directory of Open Access Journals (Sweden)

    Jeniel E. Nett

    2016-03-01

    Full Text Available Candida spp. are among the most common nosocomial fungal pathogens and are notorious for their propensity toward biofilm formation. When growing on a medical device or mucosal surface, these organisms reside as communities embedded in a protective matrix, resisting host defenses. The host responds to Candida biofilm by depositing a variety of proteins that become incorporated into the biofilm matrix. Compared to free-floating Candida, leukocytes are less effective against Candida within a biofilm. This review highlights recent advances describing the host’s response to Candida biofilms using ex vivo and in vivo models of mucosal and device-associated biofilm infections.

  12. Actinomyces naeslundii in initial dental biofilm formation.

    Science.gov (United States)

    Dige, I; Raarup, M K; Nyengaard, J R; Kilian, M; Nyvad, B

    2009-07-01

    The combined use of confocal laser scanning microscopy (CLSM) and fluorescent in situ hybridization (FISH) offers new opportunities for analysis of the spatial relationships and temporal changes of specific members of the microbiota of intact dental biofilms. The purpose of this study was to analyse the patterns of colonization and population dynamics of Actinomyces naeslundii compared to streptococci and other bacteria during the initial 48 h of biofilm formation in the oral cavity. Biofilms developed on standardized glass slabs mounted in intra-oral appliances worn by ten individuals for 6, 12, 24 and 48 h. The biofilms were subsequently labelled with probes against A. naeslundii (ACT476), streptococci (STR405) or all bacteria (EUB338), and were analysed by CLSM. Labelled bacteria were quantified by stereological tools. The results showed a notable increase in the number of streptococci and A. naeslundii over time, with a tendency towards a slower growth rate for A. naeslundii compared with streptococci. A. naeslundii was located mainly in the inner part of the multilayered biofilm, indicating that it is one of the species that attaches directly to the acquired pellicle. The participation of A. naeslundii in the initial stages of dental biofilm formation may have important ecological consequences. PMID:19406899

  13. Biofilm formation of Francisella noatunensis subsp. orientalis

    Science.gov (United States)

    Soto, Esteban; Halliday-Wimmonds, Iona; Kearney, Michael T; Hansen, John D.

    2015-01-01

    Francisella noatunensis subsp. orientalis (Fno) is an emergent fish pathogen in both marine and fresh water environments. The bacterium is suspected to persist in the environment even without the presence of a suitable fish host. In the present study, the influence of different abiotic factors such as salinity and temperature were used to study the biofilm formation of different isolates of Fno including intracellular growth loci C (iglC)and pathogenicity determinant protein A (pdpA) knockout strains. Finally, we compared the susceptibility of planktonic and biofilm to three disinfectants used in the aquaculture and ornamental fish industry, namely Virkon®, bleach and hydrogen peroxide. The data indicates that Fno is capable of producing biofilms within 24 h where both salinity as well as temperature plays a role in the growth and biofilm formation of Fno. Mutations in theiglC or pdpA, both known virulence factors, do not appear to affect the capacity of Fno to produce biofilms, and the minimum inhibitory concentration, and minimum biocidal concentration for the three disinfectants were lower than the minimum biofilm eradication concentration values. This information needs to be taken into account if trying to eradicate the pathogen from aquaculture facilities or aquariums.

  14. Biofilm formation of Francisella noatunensis subsp. orientalis.

    Science.gov (United States)

    Soto, Esteban; Halliday-Simmonds, Iona; Francis, Stewart; Kearney, Michael T; Hansen, John D

    2015-12-31

    Francisella noatunensis subsp. orientalis (Fno) is an emergent fish pathogen in both marine and fresh water environments. The bacterium is suspected to persist in the environment even without the presence of a suitable fish host. In the present study, the influence of different abiotic factors such as salinity and temperature were used to study the biofilm formation of different isolates of Fno including intracellular growth loci C (iglC) and pathogenicity determinant protein A (pdpA) knockout strains. Finally, we compared the susceptibility of planktonic and biofilm to three disinfectants used in the aquaculture and ornamental fish industry, namely Virkon(®), bleach and hydrogen peroxide. The data indicates that Fno is capable of producing biofilms within 24 h where both salinity as well as temperature plays a role in the growth and biofilm formation of Fno. Mutations in the iglC or pdpA, both known virulence factors, do not appear to affect the capacity of Fno to produce biofilms, and the minimum inhibitory concentration, and minimum biocidal concentration for the three disinfectants were lower than the minimum biofilm eradication concentration values. This information needs to be taken into account if trying to eradicate the pathogen from aquaculture facilities or aquariums. PMID:26507830

  15. Candida/Candida biofilms. First description of dual-species Candida albicans/C. rugosa biofilm.

    Science.gov (United States)

    Martins, Carlos Henrique Gomes; Pires, Regina Helena; Cunha, Aline Oliveira; Pereira, Cristiane Aparecida Martins; Singulani, Junya de Lacorte; Abrão, Fariza; Moraes, Thais de; Mendes-Giannini, Maria José Soares

    2016-04-01

    Denture liners have physical properties that favour plaque accumulation and colonization by Candida species, irritating oral tissues and causing denture stomatitis. To isolate and determine the incidence of oral Candida species in dental prostheses, oral swabs were collected from the dental prostheses of 66 patients. All the strains were screened for their ability to form biofilms; both monospecies and dual-species combinations were tested. Candida albicans (63 %) was the most frequently isolated microorganism; Candida tropicalis (14 %), Candida glabrata (13 %), Candida rugosa (5 %), Candida parapsilosis (3 %), and Candida krusei (2 %) were also detected. The XTT assay showed that C. albicans SC5314 possessed a biofilm-forming ability significantly higher (p biofilm was less than the total CFU of a monospecies C. albicans biofilm. In contrast to the profuse hyphae verified in monospecies C. albicans biofilms, micrographies showed that the C. albicans/non-albicans Candida biofilms consisted of sparse yeast forms and profuse budding yeast cells that generated a network. These results suggested that C. albicans and the tested Candida species could co-exist in biofilms displaying apparent antagonism. The study provide the first description of C. albicans/C. rugosa mixed biofilm.

  16. Formation of biofilms under phage predation: considerations concerning a biofilm increase.

    Science.gov (United States)

    Hosseinidoust, Zeinab; Tufenkji, Nathalie; van de Ven, Theo G M

    2013-01-01

    Bacteriophages are emerging as strong candidates for combating bacterial biofilms. However, reports indicating that host populations can, in some cases, respond to phage predation by an increase in biofilm formation are of concern. This study investigates whether phage predation can enhance the formation of biofilm and if so, if this phenomenon is governed by the emergence of phage-resistance or by non-evolutionary mechanisms (eg spatial refuge). Single-species biofilms of three bacterial pathogens (Pseudomonas aeruginosa, Salmonella enterica serotype Typhimurium, and Staphylococcus aureus) were pretreated and post-treated with species-specific phages. Some of the phage treatments resulted in an increase in the levels of biofilm of their host. It is proposed that the phenotypic change brought about by acquiring phage resistance is the main reason for the increase in the level of biofilm of P. aeruginosa. For biofilms of S. aureus and S. enterica Typhimurium, although resistance was detected, increased formation of biofilm appeared to be a result of non-evolutionary mechanisms.

  17. BiofilmQuant: a computer-assisted tool for dental biofilm quantification.

    Science.gov (United States)

    Mansoor, Awais; Patsekin, Valery; Scherl, Dale; Robinson, J Paul; Rajwa, Bartlomiej

    2014-01-01

    Dental biofilm is the deposition of microbial material over a tooth substratum. Several methods have recently been reported in the literature for biofilm quantification; however, at best they provide a barely automated solution requiring significant input needed from the human expert. On the contrary, state-of-the-art automatic biofilm methods fail to make their way into clinical practice because of the lack of effective mechanism to incorporate human input to handle praxis or misclassified regions. Manual delineation, the current gold standard, is time consuming and subject to expert bias. In this paper, we introduce a new semi-automated software tool, BiofilmQuant, for dental biofilm quantification in quantitative light-induced fluorescence (QLF) images. The software uses a robust statistical modeling approach to automatically segment the QLF image into three classes (background, biofilm, and tooth substratum) based on the training data. This initial segmentation has shown a high degree of consistency and precision on more than 200 test QLF dental scans. Further, the proposed software provides the clinicians full control to fix any misclassified areas using a single click. In addition, BiofilmQuant also provides a complete solution for the longitudinal quantitative analysis of biofilm of the full set of teeth, providing greater ease of usability.

  18. Festigkeitstheorien von anisotropen Stoffen mit sprödem Bruchverhalten

    Directory of Open Access Journals (Sweden)

    SZALAI, József

    2008-01-01

    Full Text Available Um die Ttragfähigkeit von Konstruktionen aus anisotropen Werkstoffenbeurteilen zu können, wird eine Festigkeitstheorie benötigt. Von den Festigkeitshypothesen, die imvorigen Jahrhundert aufgestellt wurden, können drei, als allgemeingültig betrachtet werden, das heisstsie können für alle Arten der Anisotropie des Werkstoffes und beliebige Spannungszuständeverwendet werden. Jede dieser Theorien kann durch eine Festigkeitsoberfläche (das ist eineHyperoberfläche im Raum der sechs Spannungskomponenten veranschaulicht werden. Jeder Punktdieser Fläche stellt einen Spannungszustand im Grenzzustand des Versagens dar und soll imFolgenden als Spannungspunkt bezeichnet werden. Für zähe Stoffe sind diese Oberflächen immerkonvex. Es ist zu beweisen, dass diese Oberflächen für Stoffe mit sprödem Bruch auch konkaveFlächenteile – im Einklang mit der Praxis – beinhalten können. Die Relationen derFestigkeitshypothesen können so umgestaltet werden, dass auf einer Seite der Bestimmungsgleichungein Ergänzungspotential, bzw. eine zu ihm proportionale Grösse bleibt. So interpretiert, behaupten dieTheorien von Mises und Tsai-Wu, dass das bis zum Bruch angehäufte Ergänzungspotential eineKonstante und somit unabhängig von der Orientierung der Hauptspannungen gegenüber derHauptachsen der Anisotropie ist. Diese unserer physikalischen Vorstellung widersprechendeSchlussfolgerung wird allein von dem Kriterium von Ashkenasi nicht gefolgt, es sagt im Gegenteilaus, dass das bis zum Bruch angehäufte Ergänzungspotential keine Konstante, sondern eine Funktionder Invarianten des Spannungszustandes und damit indirekt der Orientierung ist. UnsereFeststellungen gelten in erster Linie für das natürliche Holz und für die Holzwerkstoffe, können aber für jeden anisotropen Stoff mit sprödem Bruchverhalten zu erweitert werden.

  19. Antimicrobial susceptibility testing in biofilm-growing bacteria.

    Science.gov (United States)

    Macià, M D; Rojo-Molinero, E; Oliver, A

    2014-10-01

    Biofilms are organized bacterial communities embedded in an extracellular polymeric matrix attached to living or abiotic surfaces. The development of biofilms is currently recognized as one of the most relevant drivers of persistent infections. Among them, chronic respiratory infection by Pseudomonas aeruginosa in cystic fibrosis patients is probably the most intensively studied. The lack of correlation between conventional susceptibility test results and therapeutic success in chronic infections is probably a consequence of the use of planktonically growing instead of biofilm-growing bacteria. Therefore, several in vitro models to evaluate antimicrobial activity on biofilms have been implemented over the last decade. Microtitre plate-based assays, the Calgary device, substratum suspending reactors and the flow cell system are some of the most used in vitro biofilm models for susceptibility studies. Likewise, new pharmacodynamic parameters, including minimal biofilm inhibitory concentration, minimal biofilm-eradication concentration, biofilm bactericidal concentration, and biofilm-prevention concentration, have been defined in recent years to quantify antibiotic activity in biofilms. Using these parameters, several studies have shown very significant quantitative and qualitative differences for the effects of most antibiotics when acting on planktonic or biofilm bacteria. Nevertheless, standardization of the procedures, parameters and breakpoints, by official agencies, is needed before they are implemented in clinical microbiology laboratories for routine susceptibility testing. Research efforts should also be directed to obtaining a deeper understanding of biofilm resistance mechanisms, the evaluation of optimal pharmacokinetic/pharmacodynamic models for biofilm growth, and correlation with clinical outcome.

  20. [Progress in study of oral biofilm dispersal-inducing agents].

    Science.gov (United States)

    Yan, Zhu; Jingmei, Yang; Dingyu, Duan; Yi, Xu

    2014-12-01

    Communities of bacteria wrapped in self-generated extracellular polymeric matrix and attached to a solid surface are known as biofilm. Biofilm formation and development can be divided into three stages: adhesion of cells to a surface, reproduction of the cells, and dispersion of cells. The procedure, which surface-attached biofilm disperses bacterial cells into the environment to colonize new sites, is defined as biofilm dispersal. Biofilm dispersal is an essential stage of biofilm life cycle. It plays an important role in the transmission of bacteria. For many pathogenic bacteria, biofilm dispersal can transform bacteria in biofilm into planktonic state and promote the spread of infection. The formation of biofilm may increase the resistance of bacteria to antimicrobial agent and host defence response compared with planktonic cells. In the oral cavity, oral microorganism can attach to the surface of oral tissue and prosthesis to form biofilm. Dental caries and periodontal disease are oral chronic infections diseases of the oral tissue. The occurrence of them has a close relationship with biofilm. The mechanism of dispersal is a hot topic in recent years. Some agents which promote dispersal might be a therapeutic potential against biofilm infections. The clinical implication of dispersal agents and potential application are promising. This article reviews the dispersal-inducing agents of oral biofilms.

  1. Charakterisierung und Anwendung von humanen, primären mikrovaskulären Endothelzellen mit erweiterter Proliferationsfähigkeit

    OpenAIRE

    Scheller, Katharina

    2013-01-01

    Das Arbeitsgebiet Tissue Engineering befasst sich mit der Klärung der Mechanismen, die der Funktionen verschiedener Gewebearten zu Grunde liegen sowie mit der Entwicklung alternativer Strategien zur Behandlung von Organversagen bzw. Organverlusten. Einer der kritischsten Punkte im Tissue Engineering ist die ausreichende Versorgung der Zellen mit Nährstoffen und Sauerstoff. Bioartifizielle Gewebe mit einer Dicke von bis zu 200 µm können mittels Diffusion ausreichend versorgt werden. Für dicker...

  2. Junge Männer mit Problemen Young Men with Problems

    Directory of Open Access Journals (Sweden)

    Friederike Schneider

    2006-11-01

    Full Text Available Die vielfältigen Verantwortungen junger jemenitischer Männer gegenüber ihren Familien stehen im Mittelpunkt dieser empirischen Untersuchung. Bei dem Werk handelt es sich um eine Lizenziatsarbeit in Form einer klassischen Ethnografie, basierend auf einer Feldforschung in den Jahren 2003 und 2004 in der Altstadt von Sana’a, Jemen. Das Fazit der gesamten Studie wird mit dem Titel Zuerst die Freunde, dann die Frau vorweggenommen.The diverse responsibilities of young Yemenite men with regard to their families are the central theme of this empirical study. This text can be described as a classic ethnography that is based on fieldwork the licentiate performed in the old town of Sana’a, Jemen in 2003 and 2004. The conclusion of the entire study is already anticipated by the title of the work: First Come the Friends, then the Wife (Zuerst die Freunde, dann die Frau.

  3. Operating experience with innovative environmental technologies; Betriebserfahrungen mit innovativen Umwelttechnologien

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, H.; Bauermeister, U.; Kliche, H.; Seiffarth, K. (comps.)

    2000-03-01

    The MUT '99 (Merseburger Umwelt-Tag) discussed modern processes, technologies and plants for treatment and utilisation of waste. The conference was attended by industrial organisations and scientific institutions. [German] Der 9. Merseburger Umwelt-Tag MUT '99 steht unter dem Motto 'Betriebserfahrungen mit innovativen Umwelttechnologien - Moderne wirtschaftliche Verfahren, Technologien und Anlagen zur Behandlung/Verwertung nichtvermeidbaren Abfalls', wobei der Begriff 'Abfall' sich letztlich auf alle Umweltmedien bezieht. Entsprechend dem Motto dieser Tagung stellen Unternehmen, Betriebe und wissenschaftliche Einrichtungen ihre Erfahrungen auf dem Gebiet der Umwelttechnologien vor, um Entwicklungen auf diesem Gebiet einer breiten Diskussion zu eroeffnen. Dabei soll es insbesondere um die Behandlung nicht vermeidbarer Abfaelle und Abwaesser gehen. (orig.)

  4. Pathophysiologie des Kollagenstoffwechsels bei Patienten mit Induratio penis plastica (IPP

    Directory of Open Access Journals (Sweden)

    Lahme S

    2000-01-01

    Full Text Available Die Pathogenese der IPP ist bis heute nicht geklärt. Histopathologische Untersuchungen zeigen, daß der Kollagenstoffwechsel eine Rolle spielt. Dies veranlaßte uns zur genauen Analyse der Kollagenstoffwechselparameter bei IPP. Bei 11 Patienten mit IPP und 11 Kontrollpersonen wurden Kollagenstoffwechselparameter (Prokollagen III [PIIIP], PMN-Elastase [PMN-E], Fibronektin [FN], Fibronektinrezeptor [FN-R] und alpha1-Proteinase-Inhibitor [alpha1-PI] im cavernösen und peripheren Blut bestimmt. PMN-E, PIIIP, FN und FN-R waren in den beiden Untersuchungsgruppen nicht unterschiedlich. Die peripher venösen unterschieden sich nicht von den cavernösen Blutproben. Sowohl im peripher venös (158,55 mg/dl als auch im cavernös entnommenen Blut (168,29 mg/dl war die Konzentration des a1-PI signifikant niedriger als in der Kontrollgruppe (214,82 mg/dl. An einem zweiten Kollektiv von 23 Patienten wurden Analysen des Phänotyps für alpha1-PI im Hinblick auf das Vorliegen von genetisch determinierten Mangelallelen vorgenommen. Hier zeigte sich kein signifikanter Unterschied zu einem Kontrollkollektiv von 19 gesunden Probanden. Die alpha1-PI Erniedrigung der IPP-Patienten ist signifikant und liegt unterhalb des Normalwertbereichs für die gesunde Population. Ein Mangel an alpha1-PI kann zur Aktivitätserhöhung der Proteasen und zum Umbau des Kollagengewebes führen. Möglicherweise kommt es zusammen mit einem lokal wirksamen Einflußfaktor schließlich zur dystrophen Kalzifikation. Die humangenetischen Untersuchungen sprechen nicht für eine genetische Determinierung des alpha1-PI-Mangels, sondern legen eine erworbene hepatische Störung nahe.

  5. Chemically Specific Cellular Imaging of Biofilm Formation

    Energy Technology Data Exchange (ETDEWEB)

    Herberg, J L; Schaldach, C; Horn, J; Gjersing, E; Maxwell, R

    2006-02-09

    This document and the accompanying manuscripts summarize the technical accomplishments for our one-year LDRD-ER effort. Biofilm forming microbes have existed on this planet for billions of years and make up 60% of the biological mass on earth. Such microbes exhibit unique biochemical pathways during biofilm formation and play important roles in human health and the environment. Microbial biofilms have been directly implicated in, for example, product contamination, energy losses, and medical infection that cost the loss of human lives and billions of dollars. In no small part due to the lack of detailed understanding, biofilms unfortunately are resistant to control, inhibition, and destruction, either through treatment with antimicrobials or immunological defense mechanisms of the body. Current biofilm research has concentrated on the study of biofilms in the bulk. This is primarily due to the lack of analytical and physical tools to study biofilms non-destructively, in three dimensions, and on the micron or sub-micron scale. This has hindered the development of a clear understanding of either the early stage mechanisms of biofilm growth or the interactions of biofilms with their environment. Enzymatic studies have deduced a biochemical reaction that results in the oxidation of reduced sulfur species with the concomitant reduction of nitrate, a common groundwater pollutant, to dinitrogen gas by the bacterium, Thiobacillus denitrificans (TD). Because of its unique involvement in biologically relevant environmental pathways, TD is scheduled for genome sequencing in the near future by the DOE's Joint Genome Institute and is of interest to DOE's Genomes to Life Program. As our ecosystem is exposed to more and more nitrate contamination large scale livestock and agricultural practices, a further understanding of biofilm formation by organisms that could alleviate these problems is necessary in order to protect out biosphere. However, in order to study this

  6. DNase I and proteinase K impair Listeria monocytogenes biofilm formation and induce dispersal of pre-existing biofilms.

    Science.gov (United States)

    Nguyen, Uyen T; Burrows, Lori L

    2014-09-18

    Current sanitation methods in the food industry are not always sufficient for prevention or dispersal of Listeria monocytogenes biofilms. Here, we determined if prevention of adherence or dispersal of existing biofilms could occur if biofilm matrix components were disrupted enzymatically. Addition of DNase during biofilm formation reduced attachment (biofilms with 100μg/ml of DNase for 24h induced incomplete biofilm dispersal, with biofilm remaining compared to control. In contrast, addition of proteinase K completely inhibited biofilm formation, and 72h biofilms-including those grown under stimulatory conditions-were completely dispersed with 100μg/ml proteinase K. Generally-regarded-as-safe proteases bromelain and papain were less effective dispersants than proteinase K. In a time course assay, complete dispersal of L. monocytogenes biofilms from both polystyrene and type 304H food-grade stainless steel occurred within 5min at proteinase K concentrations above 25μg/ml. These data confirm that both DNA and proteins are required for L. monocytogenes biofilm development and maintenance, and that these components of the biofilm matrix can be targeted for effective prevention and removal of biofilms.

  7. Patient mit Ostiumstenose-Hauptstamm und Bifurkationsstenose - R. interventricularis anterior / R. diagonalis

    Directory of Open Access Journals (Sweden)

    Kerschner K

    2005-01-01

    Full Text Available Die Indikation zu Eingriffen am Hauptstamm und komplexen Bifurkationsstenosen wird auch nach Einführung von Drug-eluting- Stents und neuen Techniken kontrovers diskutiert. Im folgenden wird über eine kombinierte Hauptstamm- und Bifurkationsintervention berichtet. Anamnese: Ein 66jähriger Patient mit seit zwei Monaten zunehmender Belastungsdyspnoe Stadium III (NYHA, verbunden mit thorakalem Oppressionsgefühl. Zustand nach zerebralem Insult mit geringen Residuen, permanentes Vorhofflimmern, unzureichend eingestellte Hypertonie, geringe Nierenfunktionseinschränkung, Hypercholesterinämie. Invasive Abklärung: Ventrikulographie: ausgedehnte Akinese diaphragmal, Hypokinesie des Restventrikels, Auswurffraktion 29 %. Angiographie: 50 % Ostiumstenose-Hauptstamm, Bifurkationsstenose R. interventricularis anterior (LAD mit dem großen 1. diagonalen Ast jeweils 90 % (echte Bifurkation Typ IV ICPS-Klassifikation, Y konfiguriert (Abb. 1. Geringe Sklerose der klein angelegten A. circumflexa, proximaler Verschluß rechte Koronararterie mit Kollateralen von links zur diffus sklerotischen Peripherie. Nach entsprechender Aufklärung über die Therapiemöglichkeiten wurde eine Bypass-Operation vom Patienten nicht gewünscht und die Intervention durchgeführt. Intervention: Führungskatheter EBU 4 7F (Launcher, Medtronic. Sondierung beider Äste mit einem BMW-Führungsdraht (Balance Middleweight, Guidant Corp. und sequentielle Vordehnung R. diagonalis und LAD mit einem 2,5 / 20 mm-Ballon (Hypro Pegaso Sorin, Biomedica mit 16 atm. Plazierung eines 2,75 / 24 mm-Taxus-Express-2-Stent (Boston Scientific im R. diagonalis und eines 3,0 / 28 mm-Taxus-Express-2-Stent im LAD und Implantation in Crush-Technik (Abb. 2, jeweils 14 atm, mit dem Stent im R. diagonalis als gecrushtem Stent. Resondierung des R. diagonalis und Vordehnung des Abganges mit einem 1,5 und 2,5 mm-Ballon mit 20 atm und anschließende Kissing-Ballondilatation R. diagonalis 2,5 mm und LAD 3,0 mm

  8. Structure, composition, and strength of nitrifying membrane-aerated biofilms

    DEFF Research Database (Denmark)

    Pellicer i Nàcher, Carles; Smets, Barth F.

    2014-01-01

    Membrane-aerated biofilm reactors (MABRs) are a novel technology based on the growth of biofilms on oxygen-permeable membranes. Hereby, MABRs combine all the advantages of biofilm growth with a more flexible and efficient control of the oxygen load. In the present work, flow cell operation...... to achieve full nitrification revealed a significantly different structure of nitrifying MABR biofilms with respect to its co-diffusion counterparts reported in the literature (up to now assumed to have similar properties). Different levels of shear stress and oxygen loadings during MABR operation also...... affected these biofilm parameters. Furthermore, reactor operation at higher oxygen loads resulted in an increase of the biofilm cohesiveness, which depended on the EPS mass in the biofilms and the type of stress applied (more cohesive against normal than shear stresses). The EPS in the strongest biofilms...

  9. Oh What a Tangled Biofilm Web Bacteria Weave

    Science.gov (United States)

    ... Inside Life Science > Oh What a Tangled Biofilm Web Bacteria Weave Inside Life Science View All Articles | Inside Life Science Home Page Oh What a Tangled Biofilm Web Bacteria Weave By Elia Ben-Ari Posted May ...

  10. Extracellular matrix structure governs invasion resistance in bacterial biofilms.

    Science.gov (United States)

    Nadell, Carey D; Drescher, Knut; Wingreen, Ned S; Bassler, Bonnie L

    2015-08-01

    Many bacteria are highly adapted for life in communities, or biofilms. A defining feature of biofilms is the production of extracellular matrix that binds cells together. The biofilm matrix provides numerous fitness benefits, including protection from environmental stresses and enhanced nutrient availability. Here we investigate defense against biofilm invasion using the model bacterium Vibrio cholerae. We demonstrate that immotile cells, including those identical to the biofilm resident strain, are completely excluded from entry into resident biofilms. Motile cells can colonize and grow on the biofilm exterior, but are readily removed by shear forces. Protection from invasion into the biofilm interior is mediated by the secreted protein RbmA, which binds mother-daughter cell pairs to each other and to polysaccharide components of the matrix. RbmA, and the invasion protection it confers, strongly localize to the cell lineages that produce it.

  11. Metagenomic Analysis of Showerhead Biofilms from a Hospital in Ohio

    Science.gov (United States)

    Background: The National Institute of Health estimated that 80% of human microbial infections are associated with biofilms. Although water supplies and hospital equipments are constantly treated with disinfectants, the presence of biofilms in these areas has been frequently obser...

  12. Strategies for antimicrobial drug delivery to biofilm.

    Science.gov (United States)

    Martin, Claire; Low, Wan Li; Gupta, Abhishek; Amin, Mohd Cairul Iqbal Mohd; Radecka, Iza; Britland, Stephen T; Raj, Prem; Kenward, Ken M A

    2015-01-01

    Biofilms are formed by the attachment of single or mixed microbial communities to a variety of biological and/or synthetic surfaces. Biofilm micro-organisms benefit from many advantages of the polymicrobial environment including increased resistance against antimicrobials and protection against the host organism's defence mechanisms. These benefits stem from a number of structural and physiological differences between planktonic and biofilm-resident microbes, but two main factors are the presence of extracellular polymeric substances (EPS) and quorum sensing communication. Once formed, biofilms begin to synthesise EPS, a complex viscous matrix composed of a variety of macromolecules including proteins, lipids and polysaccharides. In terms of drug delivery strategies, it is the EPS that presents the greatest barrier to diffusion for drug delivery systems and free antimicrobial agents alike. In addition to EPS synthesis, biofilm-based micro-organisms can also produce small, diffusible signalling molecules involved in cell density-dependent intercellular communication, or quorum sensing. Not only does quorum sensing allow microbes to detect critical cell density numbers, but it also permits co-ordinated behaviour within the biofilm, such as iron chelation and defensive antibiotic activities. Against this backdrop of microbial defence and cell density-specific communication, a variety of drug delivery systems have been developed to deliver antimicrobial agents and antibiotics to extracellular and/or intracellular targets, or more recently, to interfere with the specific mechanisms of quorum sensing. Successful delivery strategies have employed lipidic and polymeric-based formulations such as liposomes and cyclodextrins respectively, in addition to inorganic carriers e.g. metal nanoparticles. This review will examine a range of drug delivery systems and their application to biofilm delivery, as well as pharmaceutical formulations with innate antimicrobial properties

  13. Ginger Extract Inhibits Biofilm Formation by Pseudomonas aeruginosa PA14

    OpenAIRE

    Han-Shin Kim; Hee-Deung Park

    2013-01-01

    Bacterial biofilm formation can cause serious problems in clinical and industrial settings, which drives the development or screening of biofilm inhibitors. Some biofilm inhibitors have been screened from natural products or modified from natural compounds. Ginger has been used as a medicinal herb to treat infectious diseases for thousands of years, which leads to the hypothesis that it may contain chemicals inhibiting biofilm formation. To test this hypothesis, we evaluated ginger's ability ...

  14. Streptococcus gordonii glucosyltransferase promotes biofilm interactions with Candida albicans

    Directory of Open Access Journals (Sweden)

    Austin Ricker

    2014-01-01

    Full Text Available Background: Candida albicans co-aggregates with Streptococcus gordonii to form biofilms and their interactions in mucosal biofilms may lead to pathogenic synergy. Although the functions of glucosyltransferases (Gtf of Mutans streptococci have been well characterized, the biological roles of these enzymes in commensal oral streptococci, such as S. gordonii, in oral biofilm communities are less clear. Objective: The objective of this work was to explore the role of GtfG, the single Gtf enzyme of S. gordonii, in biofilm interactions with C. albicans. Design: Biofilms were grown under salivary flow in flow cells in vitro, or under static conditions in 96 well plates. A panel of isogenic S. gordonii CH1 gtfG mutants and complemented strains were co-inoculated with C. albicans strain SC5314 to form mixed biofilms. Biofilm accretion and binding interactions between the two organisms were tested. Biofilms were quantified using confocal microscopy or the crystal violet assay. Results: The presence of GtfG enhanced dual biofilm accretion, and sucrose supplementation further augmented dual biofilm formation, pointing to a role of newly synthesized glucans. GtfG also promoted binding to C. albicans preformed biofilms. Soluble α-1,6-glucans played a role in these interactions since: 1 a strain producing only soluble glucans (CH107 formed robust dual biofilms under conditions of salivary flow; and 2 the dual biofilm was susceptible to enzymatic breakdown by dextranase which specifically degrades soluble α-1,6-glucans. Conclusion: Our work identified a novel molecular mechanism for C. albicans and S. gordonii biofilm interactions, mediated by GtfG. This protein promotes early biofilm binding of S. gordonii to C. albicans which leads to increased accretion of streptococcal cells in mixed biofilms. We also showed that soluble glucans, with α-1,6-linkages, promoted inter-generic adhesive interactions.

  15. Biofilms and Wounds: An Overview of the Evidence

    OpenAIRE

    Percival, Steven L.; McCarty, Sara M.; Lipsky, Benjamin

    2015-01-01

    Significance: Microorganisms can exist both in the planktonic and biofilm state. Each phenotypic state has a role to play in delaying healing and causing infections of both acute and chronic wounds. However, the virulent biofilm state is the fundamental reason that chronic wounds do not heal in a timely manner. We hypothesize that because microorganisms attach to any surface, biofilms can be found in all chronic wounds. However, it is not the biofilm per se that represents the greatest obstac...

  16. Biofilm delays wound healing: A review of the evidence

    OpenAIRE

    Metcalf, Daniel G.; Philip G Bowler

    2014-01-01

    Biofilm is the predominant mode of life for bacteria and today it is implicated in numerous human diseases. A growing body of scientific and clinical evidence now exists regarding the presence of biofilm in wounds. This review summarizes the clinical experiences and in vivo evidence that implicate biofilm in delayed wound healing. The various mechanisms by which biofilm may impede healing are highlighted, including impaired epithelialization and granulation tissue formation, and reduced susce...

  17. The Composition and Metabolic Phenotype of Neisseria gonorrhoeae Biofilms

    Directory of Open Access Journals (Sweden)

    Michael A Apicella

    2011-04-01

    Full Text Available N. gonorrhoeae has been shown to form biofilms during cervical infection. Thus, biofilm formation may play an important role in the infection of women. The ability of N. gonorrhoeae to form membrane blebs is crucial to biofilm formation. Blebs contain DNA and outer membrane structures, which have been shown to be major constituents of the biofilm matrix. The organism expresses a DNA thermonuclease that is involved in remodeling of the biofilm matrix. Comparison of the transcriptional profiles of gonococcal biofilms and planktonic runoff indicate that genes involved in anaerobic metabolism and oxidative stress tolerance are more highly expressed in biofilm. The expression of aniA, ccp, and norB, which encode nitrite reductase, cytochrome c peroxidase, and nitric oxide reductase respectively, is required for mature biofilm formation over glass and human cervical cells. In addition, anaerobic respiration occurs in the substratum of gonococcal biofilms and disruption of the norB gene required for anaerobic respiration, results in a severe biofilm attenuation phenotype. It has been demonstrated that accumulation of nitric oxide (NO contributes to the phenotype of a norB mutant and can retard biofilm formation. However, NO can also enhance biofilm formation, and this is largely dependent on the concentration and donation rate or steady state kinetics of NO. The majority of the genes involved in gonococcal oxidative stress tolerance are also required for normal biofilm formation, as mutations in the following genes result in attenuated biofilm formation over cervical cells and/or glass: oxyR, gor, prx, mntABC, trxB, and estD. Overall, biofilm formation appears to be an adaptation for coping with the environmental stresses present in the female genitourinary tract. Therefore, this review will discuss the studies, which describe the composition and metabolic phenotype of gonococcal biofilms.

  18. Inseltransplantation als Therapieoption bei Diabetes mellitus Typ 1: Für wen, mit welchem Ziel, mit welchem Erfolg?

    Directory of Open Access Journals (Sweden)

    Ludwig B

    2014-01-01

    Full Text Available Die Inseltransplantation hat sich als Behandlungsoption für Patienten mit Diabetes mellitus Typ 1 etabliert. In den meisten Zentren wird die Indikation gestellt, wenn konventionelle Therapiemethoden versagen und Patienten durch eine hochlabile Stoffwechsellage und rezidivierende Hypoglykämien gefährdet sind. Hintergrund für diese strikte Indikationsstellung ist die Notwendigkeit einer dauerhaften Immunsuppression und der kritische Mangel an verfügbaren Spenderorganen. Durch die Wiederherstellung einer endogenen Insulinsekretion kommt es zu einer zuverlässigen Stabilisierung des Blutzuckerprofils, Vermeidung von Hypoglykämien und Verhinderung bzw. Stabilisierung von Spätkomplikationen. Damit einher geht eine deutliche Verbesserung der Lebensqualität. Das Erreichen einer kompletten Insulinunabhängigkeit ist dabei nicht vorrangiges Therapieziel.

  19. Aktuelles aus der Forschung mit menschlichen embryonalen Stammzellen (Mit dem Jahresbericht 2004 der Zentralen Ethikkommission für Stammzellenforschung

    Directory of Open Access Journals (Sweden)

    Beier HM

    2005-01-01

    Full Text Available Im internationalen Diskurs über die Forschung mit menschlichen embryonalen Stammzellen und die Perspektiven, regenerative Therapien zu entwickeln, fanden sich in jüngster Zeit bemerkenswerte Beiträge, auf die wir hier zurückgreifen. In den aufstrebenden Forschungsnationen Südkorea, Taiwan, Singapur und China läuft ein enormer Wettbewerb um die umfangreichsten Forschungsressourcen und die Führung in der embryonalen Stammzellforschung ab. In Europa und in den USA investieren Wissenschaftler Zeit, Forschungsmittel und intellektuelle Kapazität in die Suche nach Wegen, humane embryonale Stammzellen herzustellen, ohne menschliche Eizellen und Embryonen für diese Verfahren opfern zu müssen. In Deutschland finden solche Bemühungen ein positives Echo, weil das Gesetz es verbietet, embryonale Stammzellen aus verwaisten Blastozysten, sog. überzähligen Embryonen, herzustellen. Dem Stammzellgesetz gemäß kann in Deutschland nur unter Ausnahmebedingungen an menschlichen embryonalen Stammzellen geforscht werden. Wissenschaftler dürfen nach Prüfung und Genehmigung eines speziellen Projektantrages durch das Robert-Koch-Institut menschliche embryonale Stammzell-Linien von bestimmten, lizensierten, ausländischen Herstellern importieren. Allerdings müssen diese Zell-Linien vor dem Stichtag, dem 1.1.2002, hergestellt worden sein. Die Zentrale Ethik-Kommission für Stammzellenforschung (ZES, die das Robert-Koch-Institut im Auftrag der Bundesregierung berät, berichtet jedes Jahr über ihre Arbeit. Im zweiten Teil dieses Artikels wird mit freundlicher Genehmigung des Bundesministeriums für Gesundheit und Soziale Sicherheit der ZES-Jahresbericht 2004 veröffentlicht.

  20. DNase I and proteinase K impair Listeria monocytogenes biofilm formation and induce dispersal of pre-existing biofilms.

    Science.gov (United States)

    Nguyen, Uyen T; Burrows, Lori L

    2014-09-18

    Current sanitation methods in the food industry are not always sufficient for prevention or dispersal of Listeria monocytogenes biofilms. Here, we determined if prevention of adherence or dispersal of existing biofilms could occur if biofilm matrix components were disrupted enzymatically. Addition of DNase during biofilm formation reduced attachment (bromelain and papain were less effective dispersants than proteinase K. In a time course assay, complete dispersal of L. monocytogenes biofilms from both polystyrene and type 304H food-grade stainless steel occurred within 5min at proteinase K concentrations above 25μg/ml. These data confirm that both DNA and proteins are required for L. monocytogenes biofilm development and maintenance, and that these components of the biofilm matrix can be targeted for effective prevention and removal of biofilms. PMID:25043896

  1. Nitritation performance and biofilm development of co- and counter-diffusion biofilm reactors: Modeling and experimental comparison

    DEFF Research Database (Denmark)

    Wang, Rongchang; Terada, Akihiko; Lackner, Susanne;

    2009-01-01

    results showed that the counter-diffusion biofilms developed faster and attained a larger maximum biofilm thickness than the co-diffusion biofilms. Under oxygen limited condition (DO L-1) and high pH (8.0-8.3), nitrite accumulation was triggered more significantly in co-diffusion than counter......-diffusion biofilms by increasing the applied ammonia loading from 0.21 to 0.78 g NH4+-N L-1 d(-1). The co- and counter-diffusion biofilms displayed very different spatial structures and population distributions after 120 days of operation. AOB were dominant throughout the biofilm depth in co-diffusion biofilms......-diffused in one geometry, they counter-diffused in the other. Mathematical simulations of these two geometries were implemented in two 1-D multispecies biofilm models using the AQUASIM software. Sensitivity analysis results showed that the oxygen mass transfer coefficient (K-i) and maximum specific growth rate...

  2. Rekonstruktion mit Netz beim komplexen Prolaps der Frau: Was hilft es der Patientin wirklich?

    Directory of Open Access Journals (Sweden)

    Hierl J

    2010-01-01

    Full Text Available Einleitung: Der komplexe Genitaldeszensus der Frau geht oftmals mit einer deutlichen Einschränkung der Lebensqualität (LQ einher. Dennoch ist der Endpunkt der meisten klinischen Analysen rein anatomischer und funktioneller Natur. In der vorliegenden Untersuchung wurden die Einflüsse der operativen Rekonstruktion mit einem Netz prospektiv auf die LQ evaluiert. Patienten und Methoden: Bei insgesamt 111 Patientinnen mit Deszensus erfolgte zwischen 08/2005 und 12/2007 eine operative Versorgung mittels vaginaler Netzeinlage (anteriorer bzw. kompletter Mesh-Repair. Die LQ wurde prospektiv prä- und postoperativ anhand standardisierter LQ-Fragebögen erfasst. Ergebnisse: Präoperativ zeigte sich bei den Patientinnen eine signifikant reduzierte LQ gegenüber einem Normalkollektiv (p 0,01. Bei 7 % der Patientinnen mit anteriorem, und bei 11 % mit komplettem Mesh-Repair lag postoperativ kein adäquates klinisches Ergebnis vor. In diesem Kollektiv zeigte sich kein signifikanter Unterschied in den LQ-Tests prä- und postoperativ. Bei gutem postoperativem Ergebnis zeigte sich in der Gruppe mit anteriorer Netzeinlage lediglich bei 45 % (p = 0,021, bei kompletter Netzeinlage nur bei 31 % (p = 0,041 eine signifikant verbesserte LQ. Bei kleiner Fallzahl und kurzem Nachbeobachtungszeitraum kann eine gültige Aussage bezüglich der LQ nach Deszensuschirurgie mit Netzeinlage jedoch noch nicht getroffen werden.

  3. Bioinspired, dynamic, structured surfaces for biofilm prevention

    Science.gov (United States)

    Epstein, Alexander K.

    Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even low surface tension commercial antimicrobials. Our study shows multiple contributing factors, including biochemical components and multiscale reentrant topography. Reliant on surface chemistry, conventional strategies for preventing biofilm only transiently affect attachment and/or are environmentally toxic. In this work, we look to Nature's antifouling solutions, such as the dynamic spiny skin of the echinoderm, and we develop a versatile surface nanofabrication platform. Our benchtop approach unites soft lithography, electrodeposition, mold deformation, and material selection to enable many degrees of freedom—material, geometric, mechanical, dynamic—that can be programmed starting from a single master structure. The mechanical properties of the bio-inspired nanostructures, verified by AFM, are precisely and rationally tunable. We examine how synthetic dynamic nanostructured surfaces control the attachment of pathogenic biofilms. The parameters governing long-range patterning of bacteria on high-aspect-ratio (HAR) nanoarrays are combinatorially elucidated, and we discover that sufficiently low effective stiffness of these HAR arrays mechanoselectively inhibits ˜40% of Pseudomonas aeruginosa biofilm attachment. Inspired by the active echinoderm skin, we design and fabricate externally actuated dynamic elastomer surfaces with active surface microtopography. We extract from a large parameter space the critical topographic length scales and actuation time scales for achieving

  4. Influence of biofilm thickness on micropollutants removal in nitrifying MBBRs

    OpenAIRE

    Torresi, Elena; Andersen, Henrik Rasmus; Smets, Barth F.; Plósz, Benedek G.; Christensson, M.

    2015-01-01

    The removal of pharmaceuticals was investigated in nitrifying Moving Bed Biofilm Reactors (MBBRs) containing carriers with different biofilm thicknesses. The biofilm with the thinnest thickness was found to have the highest nitrification and biotransformation rate for some key pharmaceuticals. Microbial analysis revealed a different relative abundance of nitrifying guilds in the different carriers, suggesting the importance of nitrite oxidizing bacteria in removal of micropollutants.

  5. Composition and architecture of biofilms on used voice prostheses

    NARCIS (Netherlands)

    Buijssen, Kevin J. D. A.; van der Laan, Bernard F. A. M.; van der Mei, Henny C.; Atema-Smit, Jelly; van den Huijssen, Pauline; Busscher, Henk J.; Harmsen, Hermie J. M.

    2012-01-01

    Background Biofilms on medical devices are a frequent reason for failure of the device. Voice prostheses in laryngectomized patients deteriorate within 3 to 4 months due to adhering biofilms, impeding proper functioning. Recently, we showed that these biofilms are dominated by Candida and lactobacil

  6. Novel entries in a fungal biofilm matrix encyclopedia

    Science.gov (United States)

    Virulence of Candida albicans is linked with its ability to form biofilms. Once established, biofilm infections are nearly impossible to eradicate. Biofilm cells live immersed in a self-produced matrix, a blend of extracellular biopolymers, many of which are uncharacterized. In this study, we conduc...

  7. Biofilm and siderophore effects on secondary waste water disinfection.

    Science.gov (United States)

    Saidi, N; Kouki, S; Mehri, I; Ben Rejeb, A; Belila, A; Hassen, A; Ouzari, H

    2011-10-01

    The efficiency of ultraviolet (UV) light disinfection of wastewater effluent using a large-scale pilot system was studied. The relationship between biofilm and siderophore production and UV doses received by Pseudomonas aeruginosa strain ATCC 15442 was determined. UV decreased pyoverdine production and enhanced biofilm production. Consequently external factors conditioned by both pyoverdine and biofilm may affect the UV effect on bacterial disinfection.

  8. A cathelicidin-2-derived peptide effectively impairs Staphylococcus epidermidis biofilms

    NARCIS (Netherlands)

    Molhoek, E.M.; Dijk, A. van; Veldhuizen, E.J.A.; Haagsman, H.P.; Bikker, F.J.

    2011-01-01

    Staphylococcus epidermidis is a major cause of nosocomial infections owing to its ability to form biofilms on the surface of medical devices. Biofilms are surface-adhered bacterial communities. In mature biofilms these communities are encased in an extracellular matrix composed of bacterial polysacc

  9. Influence of Streptococcus mutans on Enterococcus faecalis Biofilm Formation

    NARCIS (Netherlands)

    Deng, Dong Mei; Hoogenkamp, Michel A.; Exterkate, Rob A. M.; Jiang, Lei Meng; van der Sluis, Lucas W. M.; ten Cate, Jacob M.; Crielaard, Wim

    2009-01-01

    Introduction: An important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of

  10. Biofilm Formation Characteristics of Pseudomonas lundensis Isolated from Meat.

    Science.gov (United States)

    Liu, Yong-Ji; Xie, Jing; Zhao, Li-Jun; Qian, Yun-Fang; Zhao, Yong; Liu, Xiao

    2015-12-01

    Biofilms formations of spoilage and pathogenic bacteria on food or food contact surfaces have attracted increasing attention. These events may lead to a higher risk of food spoilage and foodborne disease transmission. While Pseudomonas lundensis is one of the most important bacteria that cause spoilage in chilled meat, its capability for biofilm formation has been seldom reported. Here, we investigated biofilm formation characteristics of P. lundensis mainly by using crystal violet staining, and confocal laser scanning microscopy (CLSM). The swarming and swimming motility, biofilm formation in different temperatures (30, 10, and 4 °C) and the protease activity of the target strain were also assessed. The results showed that P. lundensis showed a typical surface-associated motility and was quite capable of forming biofilms in different temperatures (30, 10, and 4 °C). The strain began to adhere to the contact surfaces and form biofilms early in the 4 to 6 h. The biofilms began to be formed in massive amounts after 12 h at 30 °C, and the extracellular polysaccharides increased as the biofilm structure developed. Compared with at 30 °C, more biofilms were formed at 4 and 10 °C even by a low bacterial density. The protease activity in the biofilm was significantly correlated with the biofilm formation. Moreover, the protease activity in biofilm was significantly higher than that of the corresponding planktonic cultures after cultured 12 h at 30 °C.

  11. Biofilm Formation on Dental Restorative and Implant Materials

    NARCIS (Netherlands)

    Busscher, H. J.; Rinastiti, M.; Siswomihardjo, W.; van der Mei, H. C.

    2010-01-01

    Biomaterials for the restoration of oral function are prone to biofilm formation, affecting oral health. Oral bacteria adhere to hydrophobic and hydrophilic surfaces, but due to fluctuating shear, little biofilm accumulates on hydrophobic surfaces in vivo. More biofilm accumulates on rough than on s

  12. High frequency ultrasound imaging of a single-species biofilm

    NARCIS (Netherlands)

    Shemesh, H.; Goertz, D. E.; van der Sluis, L. W. M.; de Jong, N.; Wu, M. K.; Wesselink, P. R.

    2007-01-01

    Objective: This study evaluated the feasibility of a high frequency ultrasound scan to examine the 3D morphology of Streptococcus mutans biofilms grown in vitro. Methods: Six 2-day S. mutans biofilms and six 7-day biofilms were grown on tissue culture membranes and on bovine dentine discs. A sterile

  13. Epithelial interleukin-8 responses to oral bacterial biofilms.

    Science.gov (United States)

    Peyyala, R; Kirakodu, S; Novak, K F; Ebersole, J L

    2011-10-01

    An in vitro model of bacterial biofilms on rigid gas-permeable contact lenses (RGPLs) was developed to challenge oral epithelial cells. This novel model provided seminal data on oral biofilm-host cell interactions, and with selected bacteria, the biofilms were more effective than their planktonic counterparts at stimulating host cell responses.

  14. Resistance of Candida albicans biofilms to antifungal agents in vitro.

    OpenAIRE

    Hawser, S. P.; Douglas, L J

    1995-01-01

    Biofilms formed by Candida albicans on small discs of catheter material were resistant to the action of five clinically important antifungal agents as determined by [3H]leucine incorporation and tetrazolium reduction assays. Fluconazole showed the greatest activity, and amphotericin B showed the least activity against biofilm cells. These findings were confirmed by scanning electron microscopy of the biofilms.

  15. Induction of beta-lactamase production in Pseudomonas aeruginosa biofilm

    DEFF Research Database (Denmark)

    Giwercman, B; Jensen, E T; Høiby, N;

    1991-01-01

    Imipenem induced high levels of beta-lactamase production in Pseudomonas aeruginosa biofilms. Piperacillin also induced beta-lactamase production in these biofilms but to a lesser degree. The combination of beta-lactamase production with other protective properties of the biofilm mode of growth...

  16. Dinosaurian soft tissues interpreted as bacterial biofilms.

    Directory of Open Access Journals (Sweden)

    Thomas G Kaye

    Full Text Available A scanning electron microscope survey was initiated to determine if the previously reported findings of "dinosaurian soft tissues" could be identified in situ within the bones. The results obtained allowed a reinterpretation of the formation and preservation of several types of these "tissues" and their content. Mineralized and non-mineralized coatings were found extensively in the porous trabecular bone of a variety of dinosaur and mammal species across time. They represent bacterial biofilms common throughout nature. Biofilms form endocasts and once dissolved out of the bone, mimic real blood vessels and osteocytes. Bridged trails observed in biofilms indicate that a previously viscous film was populated with swimming bacteria. Carbon dating of the film points to its relatively modern origin. A comparison of infrared spectra of modern biofilms with modern collagen and fossil bone coatings suggests that modern biofilms share a closer molecular make-up than modern collagen to the coatings from fossil bones. Blood cell size iron-oxygen spheres found in the vessels were identified as an oxidized form of formerly pyritic framboids. Our observations appeal to a more conservative explanation for the structures found preserved in fossil bone.

  17. Microbial Biofilms: Persisters, Tolerance and Dosing

    Science.gov (United States)

    Cogan, N. G.

    2005-03-01

    Almost all moist surfaces are colonized by microbial biofilms. Biofilms are implicated in cross-contamination of food products, biofouling, medical implants and various human infections such as dental cavities, ulcerative colitis and chronic respiratory infections. Much of current research is focused on the recalcitrance of biofilms to typical antibiotic and antimicrobial treatments. Although the polymer component of biofilms impedes the penetration of antimicrobials through reaction-diffusion limitation, this does not explain the observed tolerance, it merely delays the action of the agent. Heterogeneities in growth-rate also slow the eradication of the bacteria since most antimicrobials are far less effective for non-growing, or slowly growing bacteria. This also does not fully describe biofilm tolerance, since heterogeneities arr primairly a result of nutrient consumption. In this investigation, we describe the formation of `persister' cells which neither grow nor die in the presence of antibiotics. We propose that the cells are of a different phenotype than typical bacterial cells and the expression of the phenotype is regulated by the growth rate and the antibiotic concentration. We describe several experiments which describe the dynamics of persister cells and which motivate a dosing protocol that calls for periodic dosing of the population. We then introduce a mathematical model, which describes the effect of such a dosing regiment and indicates that the relative dose/withdrawal times are important in determining the effectiveness of such a treatment. A reduced model is introduced and the similar behavior is demonstrated analytically.

  18. Electrochemical sensors for biofilm and biocorrosion

    Energy Technology Data Exchange (ETDEWEB)

    Tribollet, B. [UPR 15 du CNRS, Universite Paris 6, 4 Place Jussieu, 75252 Paris Cedex05 (France)

    2003-07-01

    The presence of biofilm modifies the electrochemical properties of the interface and the mass transport near the interface. Two biofilm effects are damageable: the reduction of heat and/or mass transfer and the biocorrosion or microbiologically influenced corrosion (MIC). Two kinds of electrochemical sensors were developed: the first kind for the biofilm detection and the second one to evaluate the MIC risk. The biofilm detection is obtained by considering either the potential modification of the interface or the mass transport modification. The mass transport modification is analysed by considering the limiting diffusion current measured on a gold electrode where the biofilm development occurs. The MIC risk is evaluated with a sensor composed of two concentric electrodes in the material under investigation (e.g. carbon steel): a small disk electrode in the centre and a large ring. In a first step, a pit is artificially initiated by applying a current through these electrodes. In a second step, the risk factors of MIC are investigated by analysing the free coupling current circulating between these two short-circuited electrodes. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  19. Kombinierte radiologisch-interventionelle und radiotherapeutische Behandlung von Patienten mit zentralen Gallengangsmalignomen

    Directory of Open Access Journals (Sweden)

    Riedmann E

    2005-01-01

    Full Text Available Einleitung: In einer retrospektiven Analyse von 24 Patienten mit inoperablen oder nicht radikal resezierten Karzinomen des Gallentraktes wurde der Einfluß einer HDR-(high-dose-rate192-Ir-Brachytherapie oder der kombinierten Tele-/Brachytherapie auf Überlebenszeit und Verbesserung der Lebensqualität untersucht. Methode und Material: Von 1996 bis 2001 wurden 24 Patienten mit einem Karzinom, welches die extrahepatischen Gallenwege obstruierte (16 Klatskin-Tumoren, 6 Gallenblasenkarzinome, 2 Metastasen eines GI-Tumors, einer palliativen Radiatio unterzogen. 14 von 24 Patienten wurden bei einem lokal fortgeschrittenen inoperablen Tumor, 5 Patienten nach einer R1-Resektion und 5 Patienten im Rezidiv behandelt. Bei allen Patienten wurde eine perkutane transhepatische Cholangiographie (PTC und anschließend die Implantation eines oder mehrerer selbstexpandierbarer Stents zur Behandlung der biliären Okklusion durchgeführt. 23 Patienten erhielten eine endoluminale Brachytherapie, 10 davon kombiniert mit einer Teletherapie; ein Patient erhielt eine alleinige Teletherapie. Im ersten Jahr wurde sechs Patienten die Brachytherapie mit einer Dosis von 15 Gray (Gy in drei Fraktionen verabreicht. Ab 1997 wurden 17 Patienten mit hyperfraktionierter Brachytherapie (2 x täglich mit einer mittleren Dosis von 20 Gy (5 x 4 Gy behandelt. Die mittlere Dosis der Teletherapie in beiden Gruppen betrug 40 Gy (Range 22–60 Gy. Ergebnisse: Das mediane Überleben für alle Patienten betrug 7,7 Monate. Patienten, die mit hyperfraktionierter Brachytherapie behandelt wurden, zeigten einen Trend zu einem verlängerten Überleben mit 11,6 Monaten verglichen mit 5,7 Monaten in der konventionell behandelten Gruppe. Die akuten Nebenwirkungen waren moderat.

  20. Erhöhter oxidativer Streß bei Patienten mit instabiler Angina pectoris

    Directory of Open Access Journals (Sweden)

    Bodlaj G

    1998-01-01

    Full Text Available Die instabile Angina pectoris führt oft zum akuten Myokardinfarkt. Da die Lipid-Peroxidation im Verdacht steht, chronische und akute Ereignisse der Atherosklerose und der koronaren Herzkrankheit zu fördern, untersuchten wir die Lipid-Peroxidations-Parameter und alpha-Toco-pherol-Spiegel bei 100 KHK-Patienten und verglichen sie mit denen einer entprechenden Kontrollgruppe. 50 konsekutive Patienten mit stabiler Angina pectoris (SAP und 50 konsekutive Patienten mit instabiler Angina pectoris (IAP wurden untersucht und mit 100 klinisch gesunden Personen verglichen. Zusätzlich zur herkömmlichen Lipid- und Lipoprotein-Analyse wurden die Lipid-Peroxidations-Produkte als Hydroperoxide und Thiobarbituric acid reactive substances (TBARS gemessen. Die konjugierten Diene wurden nur bei den Patienten bestimmt. Da alpha-Tocopherol eines der wichtigsten Antioxidantien ist, wurde es ebenfalls quantifiziert. Wie erwartet hatten die Patienten wesentlich höhere Cholesterin-, Triglyzerid-, LDL-C- und Lp(a-Spiegel und niedrigere HDL-C-Spiegel als die Kontrollgruppe. Als die Patienten in Gruppen mit stabiler und instabiler Angina pectoris geteilt wurden, waren Peroxide und TBARS in der letzteren Gruppe wesentlich höher als bei den anderen Patienten und der Kontrollgruppe. Auch konjugierte Diene waren eindeutig höher bei den Patienten mit instabiler Angina pectoris. Der alpha-Tocopherol-Gesamtspiegel war in allen 3 Gruppen vergleichbar, aber der alpha-Tocopherol-Gehalt pro LDL-Partikel war bei den Patienten mit IAP am niedrigsten, gefolgt von denen mit SAP und der Kontrollgruppe. Wir schließen daraus, daß die Lipid-Peroxidations-Parameter bei Patienten mit IAP erhöht sind und SAP-Patienten von IAP-Patienten unterscheiden.

  1. Effect of glucose on Listeria monocytogenes biofilm formation, and assessment of the biofilm's sanitation tolerance.

    Science.gov (United States)

    Kyoui, Daisuke; Hirokawa, Eri; Takahashi, Hajime; Kuda, Takashi; Kimura, Bon

    2016-08-01

    Listeria monocytogenes is an important cause of human foodborne infections and its ability to form biofilms is a serious concern to the food industry. To reveal the effect of glucose conditions on biofilm formation of L. monocytogenes, 20 strains were investigated under three glucose conditions (0.1, 1.0, and 2.0% w v(-1)) by quantifying the number of cells in the biofilm and observing the biofilm structure after incubation for 24, 72, and 168 h. In addition, the biofilms were examined for their sensitivity to sodium hypochlorite. It was found that high concentrations of glucose reduced the number of viable cells in the biofilms and increased extracellular polymeric substance production. Moreover, biofilms formed at a glucose concentration of 1.0 or 2.0% were more resistant to sodium hypochlorite than those formed at a glucose concentration of 0.1%. This knowledge can be used to help design the most appropriate sanitation strategy. PMID:27353113

  2. Chlorine dioxide disinfection of single and dual species biofilms, detached biofilm and planktonic cells.

    Science.gov (United States)

    Behnke, Sabrina; Camper, Anne K

    2012-01-01

    Disinfection efficacy testing is usually done with planktonic cells or more recently, biofilms. While disinfectants are much less effective against biofilms compared to planktonic cells, questions regarding the disinfection tolerance of detached biofilm clusters remain largely unanswered. Burkholderia cepacia and Pseudomonas aeruginosa were grown in chemostats and biofilm tubing reactors, with the tubing reactor serving as a source of detached biofilm clusters. Chlorine dioxide susceptibility was assessed for B. cepacia and P. aeruginosa in these three sample types as monocultures and binary cultures. Similar doses of chlorine dioxide inactivated samples of chemostat and tubing reactor effluent and no statistically significant difference between the log(10) reductions was found. This contrasts with chlorine, shown previously to be generally less effective against detached biofilm particles. Biofilms were more tolerant and required chlorine dioxide doses ten times higher than chemostat and tubing reactor effluent samples. A second species was advantageous in all sample types and resulted in lower log(10) reductions when compared to the single species cultures, suggesting a beneficial interaction of the species.

  3. Patterned biofilm formation reveals a mechanism for structural heterogeneity in bacterial biofilms.

    Science.gov (United States)

    Gu, Huan; Hou, Shuyu; Yongyat, Chanokpon; De Tore, Suzanne; Ren, Dacheng

    2013-09-01

    Bacterial biofilms are ubiquitous and are the major cause of chronic infections in humans and persistent biofouling in industry. Despite the significance of bacterial biofilms, the mechanism of biofilm formation and associated drug tolerance is still not fully understood. A major challenge in biofilm research is the intrinsic heterogeneity in the biofilm structure, which leads to temporal and spatial variation in cell density and gene expression. To understand and control such structural heterogeneity, surfaces with patterned functional alkanthiols were used in this study to obtain Escherichia coli cell clusters with systematically varied cluster size and distance between clusters. The results from quantitative imaging analysis revealed an interesting phenomenon in which multicellular connections can be formed between cell clusters depending on the size of interacting clusters and the distance between them. In addition, significant differences in patterned biofilm formation were observed between wild-type E. coli RP437 and some of its isogenic mutants, indicating that certain cellular and genetic factors are involved in interactions among cell clusters. In particular, autoinducer-2-mediated quorum sensing was found to be important. Collectively, these results provide missing information that links cell-to-cell signaling and interaction among cell clusters to the structural organization of bacterial biofilms.

  4. Characterization of Pleurotus ostreatus biofilms by using the calgary biofilm device.

    Science.gov (United States)

    Pesciaroli, Lorena; Petruccioli, Maurizio; Fedi, Stefano; Firrincieli, Andrea; Federici, Federico; D'Annibale, Alessandro

    2013-10-01

    The adequacy of the Calgary biofilm device, often referred to as the MBEC system, as a high-throughput approach to the production and subsequent characterization of Pleurotus ostreatus biofilms was assessed. The hydroxyapatite-coating of pegs was necessary to enable biofilm attachment, and the standardization of vegetative inocula ensured a uniform distribution of P. ostreatus biofilms, which is necessary for high-throughput evaluations of several antimicrobials and exposure conditions. Scanning electron microscopy showed surface-associated growth, the occurrence of a complex aggregated growth organized in multilayers or hyphal bundles, and the encasement of hyphae within an extracellular matrix (ECM), the extent of which increased with time. Chemical analyses showed that biofilms differed from free-floating cultures for their higher contents of total sugars (TS) and ECM, with the latter being mainly composed of TS and, to a lesser extent, protein. Confocal laser scanning microscopy analysis of 4-day-old biofilms showed the presence of interspersed interstitial voids and water channels in the mycelial network, the density and compactness of which increased after a 7-day incubation, with the novel occurrence of ECM aggregates with an α-glucan moiety. In 4- and 7-day-old biofilms, tolerance to cadmium was increased by factors of 3.2 and 11.1, respectively, compared to coeval free-floating counterparts.

  5. Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci.

    Science.gov (United States)

    Stepanović, Srdjan; Vuković, Dragana; Hola, Veronika; Di Bonaventura, Giovanni; Djukić, Slobodanka; Cirković, Ivana; Ruzicka, Filip

    2007-08-01

    The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories.

  6. Anti-Biofilm and Immunomodulatory Activities of Peptides That Inhibit Biofilms Formed by Pathogens Isolated from Cystic Fibrosis Patients

    OpenAIRE

    César de la Fuente-Núñez; Sarah C. Mansour; Zhejun Wang; Lucy Jiang; Breidenstein, Elena B. M.; Melissa Elliott; Fany Reffuveille; Speert, David P.; Reckseidler-Zenteno, Shauna L.; Ya Shen; Markus Haapasalo; Robert E W Hancock

    2014-01-01

    Cystic fibrosis (CF) patients often acquire chronic respiratory tract infections due to Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) species. In the CF lung, these bacteria grow as multicellular aggregates termed biofilms. Biofilms demonstrate increased (adaptive) resistance to conventional antibiotics, and there are currently no available biofilm-specific therapies. Using plastic adherent, hydroxyapatite and flow cell biofilm models coupled with confocal and scanning electro...

  7. Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci.

    Science.gov (United States)

    Stepanović, Srdjan; Vuković, Dragana; Hola, Veronika; Di Bonaventura, Giovanni; Djukić, Slobodanka; Cirković, Ivana; Ruzicka, Filip

    2007-08-01

    The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories. PMID:17696944

  8. Star in Deep Freeze Chills Theory, MIT Researchers Report

    Science.gov (United States)

    2001-09-01

    CAMBRIDGE, Mass. -- Like a frozen turkey that just won't thaw, a strange star near the center of the Milky Way is surprising MIT experts and colleagues with its remarkably low temperature. The odd behavior is chilling current theories of stellar physics. A famously battered neutron star named KS 1731-260 appears no hotter than some of its tranquil brethren, despite enduring the heat of constant thermonuclear explosions with the force of billions of hydrogen bombs every second across a region only a few miles wide for the past 12 years. Dr. Rudi Wijnands, an astrophysicist at MIT's Center for Space Research, used the Chandra X-ray Observatory to measure the temperature of the neutron star at a very opportune moment, only months after the nuclear war apparently ended and the smoke cleared. He presented his team's findings September 5 in Washington, D.C. at a scientific conference entitled "Two Years of Science with Chandra." "Twelve years of constant thermonuclear explosions: One would think that would heat things up," said Wijnands. "This leaves us wondering whether some neutron stars are in the freezer for a much longer time than previously thought and consequently take a long time to heat up, or whether they cool down incredibly fast. Either explanation has profound implications for our field." Neutron stars are the dense, core remains of stars once many times more massive than our Sun. They are created in dazzling supernovas, in which the outer shell of the star explodes into space, and the core, containing about as much mass as the Sun, implodes and collapses into a sphere no wider than Cambridge, Massachusetts. Despite their tiny size, neutron stars are visible in several ways. One is through accretion. Neutron stars are a strong source of gravity. When they exist in binary star systems, such as KS 1731-260, they can attract the gas from what is often a "healthy" hydrogen-burning companion star (although the nature of KS 1731-260's companion is not clear.) Gas

  9. A novel approach for harnessing biofilm communities in moving bed biofilm reactors for industrial wastewater treatment

    Directory of Open Access Journals (Sweden)

    Joe A. Lemire

    2015-10-01

    Full Text Available Moving bed biofilm reactors (MBBRs are an effective biotechnology for treating industrial wastewater. Biomass retention on moving bed biofilm reactor (MBBR carriers (biofilm support materials, allows for the ease-of-operation and high treatment capacity of MBBR systems. Optimization of MBBR systems has largely focused on aspects of carrier design, while little attention has been paid to enhancing strategies for harnessing microbial biomass. Previously, our research group demonstrated that mixed-species biofilms can be harvested from an industrial wastewater inoculum [oil sands process water (OSPW] using the Calgary Biofilm Device (CBD. Moreover, the resultant biofilm communities had the capacity to degrade organic toxins (naphthenic acids—NAs that are found in OSPW. Therefore, we hypothesized that harnessing microbial communities from industrial wastewater, as biofilms, on MBBR carriers may be an effective method to bioremediate industrial wastewater.Here, we detail our methodology adapting the workflow employed for using the CBD, to generate inoculant carriers to seed an MBBR.In this study, OSPW-derived biofilm communities were successfully grown, and their efficacy evaluated, on commercially available MBBR carriers affixed within a modified CBD system. The resultant biofilms demonstrated the capacity to transfer biomass to recipient carriers within a scaled MBBR. Moreover, MBBR systems inoculated in this manner were fully active 2 days post-inoculation, and readily degraded a select population of NAs. Together, these findings suggest that harnessing microbial communities on carriers affixed within a modified CBD system may represent a facile and rapid method for obtaining functional inoculants for use in wastewater MBBR treatment systems.

  10. Entwicklung und Charakterisierung eines Prozesses zur thermischen Atomlagenabscheidung von Ruthenium mit in-situ Messtechnik

    OpenAIRE

    Junige, Marcel

    2011-01-01

    Ruthenium und sein elektrisch leitfähiges Rutheniumdioxid sind viel versprechende Kandidaten als Elektrodenmaterial in MIM (Metall-Isolator-Metall-)Kondensatoren mit Dielektrika hoher Permittivität der nächsten Generation von DRAM-Speichern, als Metall-Gate-Elektroden in p-Kanal-MOS-Transistoren mit Dielektrika hoher Permittivität, oder als Keimschicht für das direkte elektrochemische Abscheiden von Kupfer-Verbindungsleitungen. Die ALD (Atomic Layer Deposition) wächst Materiallagen mit wen...

  11. Role of Biofilm Roughness and Hydrodynamic Conditions in Legionella pneumophila Adhesion to and Detachment from Simulated Drinking Water Biofilms

    OpenAIRE

    Shen, Yun; Monroy, Guillermo L.; Derlon, Nicolas; Janjaroen, Dao; Huang, Conghui; Morgenroth, Eberhard; Boppart, Stephen A.; Ashbolt, Nicholas J.; Liu, Wen-Tso; Nguyen, Thanh H.

    2015-01-01

    Biofilms in drinking water distribution systems (DWDS) could exacerbate the persistence and associated risks of pathogenic Legionella pneumophila (L. pneumophila), thus raising human health concerns. However, mechanisms controlling adhesion and subsequent detachment of L. pneumophila associated with biofilms remain unclear. We determined the connection between L. pneumophila adhesion and subsequent detachment with biofilm physical structure characterization using optical coherence tomography ...

  12. pH, redox potential and local biofilm potential microenvironments within Geobacter sulfurreducens biofilms and their roles in electron transfer.

    Science.gov (United States)

    Babauta, Jerome T; Nguyen, Hung Duc; Harrington, Timothy D; Renslow, Ryan; Beyenal, Haluk

    2012-10-01

    The limitation of pH inside electrode-respiring biofilms is a well-known concept. However, little is known about how pH and redox potential are affected by increasing current inside biofilms respiring on electrodes. Quantifying the variations in pH and redox potential with increasing current is needed to determine how electron transfer is tied to proton transfer within the biofilm. In this research, we quantified pH and redox potential variations in electrode-respiring Geobacter sulfurreducens biofilms as a function of respiration rates, measured as current. We also characterized pH and redox potential at the counter electrode. We concluded that (1) pH continued to decrease in the biofilm through different growth phases, showing that the pH is not always a limiting factor in a biofilm and (2) decreasing pH and increasing redox potential at the biofilm electrode were associated only with the biofilm, demonstrating that G. sulfurreducens biofilms respire in a unique internal environment. Redox potential inside the biofilm was also compared to the local biofilm potential measured by a graphite microelectrode, where the tip of the microelectrode was allowed to acclimatize inside the biofilm.

  13. Anti-Biofilm and Immunomodulatory Activities of Peptides That Inhibit Biofilms Formed by Pathogens Isolated from Cystic Fibrosis Patients.

    Science.gov (United States)

    de la Fuente-Núñez, César; Mansour, Sarah C; Wang, Zhejun; Jiang, Lucy; Breidenstein, Elena B M; Elliott, Melissa; Reffuveille, Fany; Speert, David P; Reckseidler-Zenteno, Shauna L; Shen, Ya; Haapasalo, Markus; Hancock, Robert E W

    2014-01-01

    Cystic fibrosis (CF) patients often acquire chronic respiratory tract infections due to Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) species. In the CF lung, these bacteria grow as multicellular aggregates termed biofilms. Biofilms demonstrate increased (adaptive) resistance to conventional antibiotics, and there are currently no available biofilm-specific therapies. Using plastic adherent, hydroxyapatite and flow cell biofilm models coupled with confocal and scanning electron microscopy, it was demonstrated that an anti-biofilm peptide 1018 prevented biofilm formation, eradicated mature biofilms and killed biofilms formed by a wide range of P. aeruginosa and B. cenocepacia clinical isolates. New peptide derivatives were designed that, compared to their parent peptide 1018, showed similar or decreased anti-biofilm activity against P. aeruginosa biofilms, but increased activity against biofilms formed by the Gram-positive bacterium methicillin resistant Staphylococcus aureus. In addition, some of these new peptide derivatives retained the immunomodulatory activity of 1018 since they induced the production of the chemokine monocyte chemotactic protein-1 (MCP-1) and suppressed lipopolysaccharide-mediated tumor necrosis factor-α (TNF-α) production by human peripheral blood mononuclear cells (PBMC) and were non-toxic towards these cells. Peptide 1018 and its derivatives provide promising leads for the treatment of chronic biofilm infections and hyperinflammatory lung disease in CF patients.

  14. Anti-Biofilm and Immunomodulatory Activities of Peptides That Inhibit Biofilms Formed by Pathogens Isolated from Cystic Fibrosis Patients

    Directory of Open Access Journals (Sweden)

    César de la Fuente-Núñez

    2014-10-01

    Full Text Available Cystic fibrosis (CF patients often acquire chronic respiratory tract infections due to Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc species. In the CF lung, these bacteria grow as multicellular aggregates termed biofilms. Biofilms demonstrate increased (adaptive resistance to conventional antibiotics, and there are currently no available biofilm-specific therapies. Using plastic adherent, hydroxyapatite and flow cell biofilm models coupled with confocal and scanning electron microscopy, it was demonstrated that an anti-biofilm peptide 1018 prevented biofilm formation, eradicated mature biofilms and killed biofilms formed by a wide range of P. aeruginosa and B. cenocepacia clinical isolates. New peptide derivatives were designed that, compared to their parent peptide 1018, showed similar or decreased anti-biofilm activity against P. aeruginosa biofilms, but increased activity against biofilms formed by the Gram-positive bacterium methicillin resistant Staphylococcus aureus. In addition, some of these new peptide derivatives retained the immunomodulatory activity of 1018 since they induced the production of the chemokine monocyte chemotactic protein-1 (MCP-1 and suppressed lipopolysaccharide-mediated tumor necrosis factor-α (TNF-α production by human peripheral blood mononuclear cells (PBMC and were non-toxic towards these cells. Peptide 1018 and its derivatives provide promising leads for the treatment of chronic biofilm infections and hyperinflammatory lung disease in CF patients.

  15. Complement activation by Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Jensen, E T; Kharazmi, A; Garred, P;

    1993-01-01

    In chronic infections, such as the bronchopulmonary Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients, bacteria persist despite an intact host immune defense and frequent antibiotic treatment. An important reason for the persistence of the bacteria is their capacity for the biofilm...... mode of growth. In this study we investigated the role of biofilms in activation of complement, a major contributor to the inflammatory process. Complement activation by P. aeruginosa was examined in a complement consumption assay, production of C3 and factor B conversion products assessed by crossed...... immuno-electrophoresis, C5a generation tested by a PMN chemotactic assay, and terminal complement complex formation measured by ELISA. Two of the four assays showed that P. aeruginosa grown in biofilm activated complement less than planktonic bacteria, and all assays showed that activation by intact...

  16. Biofilms and their effect on local chemistry

    International Nuclear Information System (INIS)

    Fouling and corrosion are frequently mediated by microorganisms attached to the metal surface and/or embedded in a gelatinous organic matrix termed a biofilm. Biofilms substantially change the local chemistry of the adjacent metal and, thereby, influence corrosion processes. The extent of changes in local chemistry is influenced by the microenvironmental conditions at the metal surface including the number and types of microorganisms present, the dissolved oxygen concentration, the flow velocity, the buffering capacity of the bulk water, and many other factors. Since microbial-influenced corrosion is generally localized, the spatial distribution or patchiness of the microbial activity also affects the corrosion processes. A unified approach to understanding and controlling biofilms and the related corrosion is presented in the context of a case study recently conducted by CCE, Inc. at a nuclear power plant site

  17. Strategy of control for bacterial biofilm processes

    Directory of Open Access Journals (Sweden)

    A. N. Mayansky

    2012-01-01

    Full Text Available Main directions of the modern search of the antibiofilm preparations aimed at adhesive bacterial reactions, control of QS-systems, influence over bis-(3’-5’-cyclic dimeric guanosine monophosphate (cdi-GMP, and secretory bacterial processes are analysed. Approaches for biofilm dispersal and increasing the sensitivity of biofilm bacteria to antimicrobial drugs are discussed. It is underlined that the majority of inhibitor molecules were studied in vitro or in infected mice experiments. It is prognosed that in future there will appear medical preparations which will help for fighting bacterial biofilms preventing their development and spreading in the host organism.

  18. Actinomyces naeslundii in intial dental biofilm formation

    DEFF Research Database (Denmark)

    Dige, Irene; Raarup, Merete Krog; Nyengaard, Jens Randel;

    2009-01-01

    Combined use of Confocal Laser Scanning Microscopy (CLSM) and Fluorescent in situ Hybridization (FISH) offers new opportunities for analysing the spatial relationships and temporal changes of specific members of microbial populations in intact dental biofilms. AIMS: The purpose of this study....... RESULTS: This study confirmed previous work that streptococci are the predominant colonizers of early dental biofilm along with A. naeslundii. There was a notable increase in the total number of bacteria, Streptococcus spp., and A. naeslundii over time with a tendency towards a slower growth rate for A......-layer dental biofilms up to 48 h definitively demonstrated that A. naeslundii preferentially occupied the inner layers. Some A. naeslundii microcolonies extended perpendicularly from the supporting surface surrounded by other bacteria forming chimneys of complex multilayered micro-colonies. CONCLUSIONS...

  19. Anwendungsbeobachtungen mit Zolmitriptan-Rapilmet in der Praxis

    Directory of Open Access Journals (Sweden)

    Wessely P

    2004-01-01

    Full Text Available Nach Darstellungen der Prinzipien der evidenzbasierten Therapie (EBM der Migräneattacken wird die besondere Bedeutung der Triptane hervorgehoben. Die Entscheidung, Triptane einzusetzen, wird nicht unter Anwendung einer starren stufenweisen Verordnung, sondern flexibel anhand von Entscheidungshilfen für eine stratifizierte Therapieplanung getroffen. Eine solche Hilfe ist z. B. der in den USA entwickelte MIDAS-Fragebogen, der übersichtlich und einfach den Gesamtkomplex der Migräne erfaßt und nicht nur den Kopfschmerz, sondern auch die begleitenden autonomen Phänomene und vor allem auch die Beeinträchtigungen im sozio-ökonomischen Formenkreis bewertet. Dadurch kann die individuell erforderliche Therapieintensität, also z. B. der Einsatz von Triptanen, einfacher abgeschätzt werden. Die vorliegende Studie ist eine offene Anwendungsbeobachtung von Zolmitriptan-Rapimelt bei 349 Migränepatienten unter Verwendung des MIDAS-Fragebogens. Nach dreimonatiger Therapie konnte eine globale Besserung im Bereich der MIDAS-Scores nachgewiesen werden, wobei der Schweregrad IV von 42,7 % auf 14,6 % abgenommen hat (insgesamt signifikant für die Verbesserung jeweils um einen MIDAS-Grad. Die Kopfschmerzfrequenz hat sich ebenfalls von 14,6 Kopfschmerztage auf 8,7 reduziert, ebenso die Intensität – gemessen auf einer VAS-Skala – von 7,3 auf 5,3. Die Nebenwirkungsrate lag unter 2 %, die subjektive Zufriedenheit mit der Gesamtwirksamkeit von Zolmitriptan-Lyotabletten wurde in der Beurteilung durch die Probanden von 49,9 % mit sehr gut und von 35,8 % als gut bewertet, lediglich 4,3 % befanden die Medikation als unzureichend. In der Behandlung von Migräneattacken läßt sich für Zolmitriptan-RM eine hohe Patientenakzeptanz und auch ein hohes Maß an Effektivität und Wirkkonsistenz nicht nur unter den strengen Kriterien einer klinischen Prüfung, sondern auch unter den Bedingungen der Alltagspraxis nachweisen.

  20. Biofilm transplantation in the deep sea.

    Science.gov (United States)

    Wagner-Döbler, Irene

    2016-05-01

    A gold rush is currently going on in microbial ecology, which is powered by the possibility to determine the full complexity of microbial communities through next-generation sequencing. Accordingly, enormous efforts are underway to describe microbiomes worldwide, in humans, animals, plants, soil, air and the ocean. While much can be learned from these studies, only experiments will finally unravel mechanisms. One of the key questions is how a microbial community is assembled from a pool of bacteria in the environment, and how it responds to change - be it the increase in CO2 concentration in the ocean, or antibiotic treatment of the gut microbiome. The study by Zhang et al. () in this issue is one of the very few that approaches this problem experimentally in the natural environment. The authors selected a habitat which is both extremely interesting and difficult to access. They studied the Thuwal Seep in the Red Sea at 850 m depth and used a remotely operated vehicle (ROV) to place a steel frame carrying substrata for biofilm growth into the brine pool and into the adjacent normal bottom water (NBW). Biofilms were allowed to develop for 3 days, and then those that had been growing in the brine pool were transported to normal bottom water and stayed there for another 3 days, and vice versa. The 'switched' biofilms were then compared with their source communities by metagenome sequencing. Strikingly, both 'switched' biofilms were now dominated by the same two species. These species were able to cope with conditions in both source ecosystems, as shown by assembly of their genomes and detection of expression of key genes. The biofilms had adapted to environmental change, rather than to brine pools or NBW. The study shows both the resilience and adaptability of biofilm communities and has implications for microbial ecology in general and even for therapeutic approaches such as transplantation of faecal microbiomes.

  1. Clay-Bacteria Systems and Biofilm Production

    Science.gov (United States)

    Steiner, J.; Alimova, A.; Katz, A.; Steiner, N.; Rudolph, E.; Gottlieb, P.

    2007-12-01

    Soil clots and the aerosol transport of bacteria and spores are promoted by the formation of biofilms (bacteria cells in an extracellular polymeric matrix). Biofilms protect microorganisms by promoting adhesion to both organic and inorganic surfaces. Time series experiments on bacteria-clay suspensions demonstrate that biofilm growth is catalyzed by the presence of hectorite in minimal growth media for the studied species: Gram negatives (Pseudomonas syringae and Escherichia coli,) and Gram positives (Staphylococcus aureus and Bacillus subtilis). Soil organisms (P. syringae, B. subtilis) and organisms found in the human population (E. coli, S. aureus) are both used to demonstrate the general applicability of clay involvement. Fluorescent images of the biofilms are acquired by staining with propidium iodide, a component of the BacLightTM Live/Dead bacterial viability staining kit (Molecular Probes, Eugene, OR). The evolving polysaccharide-rich biofilm reacts with the clay interlayer site causing a complex substitution of the two-water hectorite interlayer with polysaccharide. The result is often a three-peak composite of the (001) x-ray diffraction maxima resulting from polysaccharide-expanded clays and an organic-driven contraction of a subset of the clays in the reaction medium. X-ray diffractograms reveal that the expanded set creates a broad maximum with clay subsets at 1.84 nm and 1.41 nm interlayer spacings as approximated by a least squares double Lorentzian fit, and a smaller shoulder at larger 2q, deriving from a contraction of the interlayer spacing. Washing with chlorox removes organic material from the contracted clay and creates a 1-water hectorite single peak in place of the double peak. The clay response can be used as an indirect indicator of biofilm in an environmental system.

  2. Investigate Nasal Colonize Staphylococcus Species Biofilm Produced

    Directory of Open Access Journals (Sweden)

    Cemil Demir

    2014-03-01

    Full Text Available Aim: 127 S.aureus and 65 CoNS strains were isolated from patients noses%u2019. To produce a biofilm ability was investigated using three different methods. Slime-positive and negative staphylococcies%u2019 resistance were evaluated against different antibiotics. Material and Method: Swap samples puted 7% blood agar. Staphylococcus aureus and coagulase-negative staphylococci (CoNS isolates biofilm produced ability were investigated using Congo Red Agar (CRA, microplates (MP and Standard Tube (ST methods. In addition to that, presence of antibiotic resistance of the staphylococcal isolates are determined agar disc diffusion method. Results: The rate of biofilm producing Staphylococcus spp strains was found to be 72.4%, 67.7%, and 62.9%, respectively with CRA, MP, and ST tests. There was no significant relationship among the tests (p>0.05. In addition, antibiotic resistance of Staphylococcus spp. against various antibiotics was also determined by the agar disk diffusion method. Resistance rates of biofilm positive (BP Staphylococcus spp for penicilin G, ampicilin, amocycilin/clavulanic acid, tetracyclin, eritromycin, gentamycin, and enrofloxacin 71.7%, 69.7%, 6.2%, 20.7%, 21.4%, 1.4%, and 0.7%, respectively. Resistance rates of biofilm negative (BN spp for 42.6%, 23.4%, 4.3%, 14.9%, 19.1%, 0.0%, 0.0% respectively. All Staphylococcus isolates were found to be susceptible to vancomycin and teicaplonin. Although BP strains antibiotic resistance rates were observed higher than BN strains. But resistance rates were not found statistically significant (p>0.05. Discussion: CRA is the reliablity and specifity method to determine Staphylococcus spp. biofilm produce ability.

  3. Confocal Raman microscopy for identification of bacterial species in biofilms

    Science.gov (United States)

    Beier, Brooke D.; Quivey, Robert G.; Berger, Andrew J.

    2011-03-01

    Implemented through a confocal microscope, Raman spectroscopy has been used to distinguish between biofilm samples of two common oral bacteria species, Streptococcus sanguinis and mutans, which are associated with healthy and cariogenic plaque, respectively. Biofilms of these species are studied as a model of dental plaque. A prediction model has been calibrated and validated using pure biofilms. This model has been used to identify the species of transferred and dehydrated samples (much like a plaque scraping) as well as hydrated biofilms in situ. Preliminary results of confocal Raman mapping of species in an intact two-species biofilm will be shown.

  4. Microbial Biofilm as a Smart Material

    DEFF Research Database (Denmark)

    Garde, Christian; Welch, Martin; Ferkinghoff-Borg, Jesper;

    2015-01-01

    Microbial biofilm colonies will in many cases form a smart material capable of responding to external threats dependent on their size and internal state. The microbial community accordingly switches between passive, protective, or attack modes of action. In order to decide which strategy to employ......, it is essential for the biofilm community to be able to sense its own size. The sensor designed to perform this task is termed a quorum sensor, since it only permits collective behaviour once a sufficiently large assembly of microbes have been established. The generic quorum sensor construct involves two genes...

  5. Effects of probiotics and antibiotics on biofilms

    OpenAIRE

    Pradeep, B.; Pandey, P K; S. Ayyappan

    2003-01-01

    Experiments were conducted to study the effects of probiotics and antibiotics on 3-months old biofilms formed on three different substrates, namely glass, granite and fiberglass reinforced plastic. The variations in heterotrophic bacterial populations associated with biofilms were monitored for a period of one month after one-time application of the probiotic Biogreen (Gee Key Marine Pvt. Ltd, Chennai) at 0.2 mg lˉ¹ and the antibiotic tetracycline at 1.0 mg lˉ¹. The variations in heterotrophi...

  6. Type IV pili promote early biofilm formation by Clostridium difficile.

    Science.gov (United States)

    Maldarelli, Grace A; Piepenbrink, Kurt H; Scott, Alison J; Freiberg, Jeffrey A; Song, Yang; Achermann, Yvonne; Ernst, Robert K; Shirtliff, Mark E; Sundberg, Eric J; Donnenberg, Michael S; von Rosenvinge, Erik C

    2016-08-01

    Increasing morbidity and mortality from Clostridium difficile infection (CDI) present an enormous challenge to healthcare systems. Clostridium difficile express type IV pili (T4P), but their function remains unclear. Many chronic and recurrent bacterial infections result from biofilms, surface-associated bacterial communities embedded in an extracellular matrix. CDI may be biofilm mediated; T4P are important for biofilm formation in a number of organisms. We evaluate the role of T4P in C. difficile biofilm formation using RNA sequencing, mutagenesis and complementation of the gene encoding the major pilin pilA1, and microscopy. RNA sequencing demonstrates that, in comparison to other growth phenotypes, C. difficile growing in a biofilm has a distinct RNA expression profile, with significant differences in T4P gene expression. Microscopy of T4P-expressing and T4P-deficient strains suggests that T4P play an important role in early biofilm formation. A non-piliated pilA1 mutant forms an initial biofilm of significantly reduced mass and thickness in comparison to the wild type. Complementation of the pilA1 mutant strain leads to formation of a biofilm which resembles the wild-type biofilm. These findings suggest that T4P play an important role in early biofilm formation. Novel strategies for confronting biofilm infections are emerging; our data suggest that similar strategies should be investigated in CDI. PMID:27369898

  7. Characterization of Mannheimia haemolytica biofilm formation in vitro.

    Science.gov (United States)

    Boukahil, Ismail; Czuprynski, Charles J

    2015-01-30

    Mannheimia haemolytica is the primary bacterial agent in the bovine respiratory disease complex. It is thought that M. haemolytica colonizes the tonsillar crypts of cattle as a commensal and subsequently descends into the lungs to cause disease. Many bacterial species persist in the host as biofilms. There is limited information about the ability of M. haemolytica to form biofilms. The aim of this study was to develop an in vitro model for M. haemolytica biofilm formation. We found that M. haemolytica required at least 36 h to form robust biofilms on plastic in vitro when incubated in RPMI-1640 tissue culture medium at 37 °C, with maximal biofilm formation being evident at 48 h. Biofilm formation was inhibited by adding the monosaccharides d(+) galactose and d(+) mannose to the growth medium. Addition of antibodies to the M. haemolytica surface protein OmpA also reduced biofilm formation. Upon evaluating the macromolecules within the biofilm extracellular polymeric substance we found it contained 9.7 μg/cm(2) of protein, 0.81 μg/cm(2) of total carbohydrate, and 0.47 μg/cm(2) of extracellular DNA. Furthermore, proteinase K treatment significantly decreased biofilms (Pbiofilms to a lesser extent. M. haemolytica biofilm cells were more resistant than planktonic cells to the antibiotics florfenicol, gentamicin, and tulathromycin. These results provide evidence that M. haemolytica can form biofilms, which could contribute to its ability to persist as a commensal in the bovine upper respiratory tract.

  8. Ginger extract inhibits biofilm formation by Pseudomonas aeruginosa PA14.

    Science.gov (United States)

    Kim, Han-Shin; Park, Hee-Deung

    2013-01-01

    Bacterial biofilm formation can cause serious problems in clinical and industrial settings, which drives the development or screening of biofilm inhibitors. Some biofilm inhibitors have been screened from natural products or modified from natural compounds. Ginger has been used as a medicinal herb to treat infectious diseases for thousands of years, which leads to the hypothesis that it may contain chemicals inhibiting biofilm formation. To test this hypothesis, we evaluated ginger's ability to inhibit Pseudomonas aeruginosa PA14 biofilm formation. A static biofilm assay demonstrated that biofilm development was reduced by 39-56% when ginger extract was added to the culture. In addition, various phenotypes were altered after ginger addition of PA14. Ginger extract decreased production of extracellular polymeric substances. This finding was confirmed by chemical analysis and confocal laser scanning microscopy. Furthermore, ginger extract formed noticeably less rugose colonies on agar plates containing Congo red and facilitated swarming motility on soft agar plates. The inhibition of biofilm formation and the altered phenotypes appear to be linked to a reduced level of a second messenger, bis-(3'-5')-cyclic dimeric guanosine monophosphate. Importantly, ginger extract inhibited biofilm formation in both Gram-positive and Gram-negative bacteria. Also, surface biofilm cells formed with ginger extract detached more easily with surfactant than did those without ginger extract. Taken together, these findings provide a foundation for the possible discovery of a broad spectrum biofilm inhibitor. PMID:24086697

  9. Ginger extract inhibits biofilm formation by Pseudomonas aeruginosa PA14.

    Directory of Open Access Journals (Sweden)

    Han-Shin Kim

    Full Text Available Bacterial biofilm formation can cause serious problems in clinical and industrial settings, which drives the development or screening of biofilm inhibitors. Some biofilm inhibitors have been screened from natural products or modified from natural compounds. Ginger has been used as a medicinal herb to treat infectious diseases for thousands of years, which leads to the hypothesis that it may contain chemicals inhibiting biofilm formation. To test this hypothesis, we evaluated ginger's ability to inhibit Pseudomonas aeruginosa PA14 biofilm formation. A static biofilm assay demonstrated that biofilm development was reduced by 39-56% when ginger extract was added to the culture. In addition, various phenotypes were altered after ginger addition of PA14. Ginger extract decreased production of extracellular polymeric substances. This finding was confirmed by chemical analysis and confocal laser scanning microscopy. Furthermore, ginger extract formed noticeably less rugose colonies on agar plates containing Congo red and facilitated swarming motility on soft agar plates. The inhibition of biofilm formation and the altered phenotypes appear to be linked to a reduced level of a second messenger, bis-(3'-5'-cyclic dimeric guanosine monophosphate. Importantly, ginger extract inhibited biofilm formation in both Gram-positive and Gram-negative bacteria. Also, surface biofilm cells formed with ginger extract detached more easily with surfactant than did those without ginger extract. Taken together, these findings provide a foundation for the possible discovery of a broad spectrum biofilm inhibitor.

  10. Removal of Dental Biofilms with an Ultrasonically Activated Water Stream.

    Science.gov (United States)

    Howlin, R P; Fabbri, S; Offin, D G; Symonds, N; Kiang, K S; Knee, R J; Yoganantham, D C; Webb, J S; Birkin, P R; Leighton, T G; Stoodley, P

    2015-09-01

    Acidogenic bacteria within dental plaque biofilms are the causative agents of caries. Consequently, maintenance of a healthy oral environment with efficient biofilm removal strategies is important to limit caries, as well as halt progression to gingivitis and periodontitis. Recently, a novel cleaning device has been described using an ultrasonically activated stream (UAS) to generate a cavitation cloud of bubbles in a freely flowing water stream that has demonstrated the capacity to be effective at biofilm removal. In this study, UAS was evaluated for its ability to remove biofilms of the cariogenic pathogen Streptococcus mutans UA159, as well as Actinomyces naeslundii ATCC 12104 and Streptococcus oralis ATCC 9811, grown on machine-etched glass slides to generate a reproducible complex surface and artificial teeth from a typodont training model. Biofilm removal was assessed both visually and microscopically using high-speed videography, confocal scanning laser microscopy (CSLM), and scanning electron microscopy (SEM). Analysis by CSLM demonstrated a statistically significant 99.9% removal of S. mutans biofilms exposed to the UAS for 10 s, relative to both untreated control biofilms and biofilms exposed to the water stream alone without ultrasonic activation (P biofilm removal. The UAS was also highly effective at S. mutans, A. naeslundii, and S. oralis biofilm removal from machine-etched glass and S. mutans from typodont surfaces with complex topography. Consequently, UAS technology represents a potentially effective method for biofilm removal and improved oral hygiene.

  11. Biofilm formation on dental restorative and implant materials.

    Science.gov (United States)

    Busscher, H J; Rinastiti, M; Siswomihardjo, W; van der Mei, H C

    2010-07-01

    Biomaterials for the restoration of oral function are prone to biofilm formation, affecting oral health. Oral bacteria adhere to hydrophobic and hydrophilic surfaces, but due to fluctuating shear, little biofilm accumulates on hydrophobic surfaces in vivo. More biofilm accumulates on rough than on smooth surfaces. Oral biofilms mostly consist of multiple bacterial strains, but Candida species are found on acrylic dentures. Biofilms on gold and amalgam in vivo are thick and fully covering, but barely viable. Biofilms on ceramics are thin and highly viable. Biofilms on composites and glass-ionomer cements cause surface deterioration, which enhances biofilm formation again. Residual monomer release from composites influences biofilm growth in vitro, but effects in vivo are less pronounced, probably due to the large volume of saliva into which compounds are released and its continuous refreshment. Similarly, conflicting results have been reported on effects of fluoride release from glass-ionomer cements. Finally, biomaterial-associated infection of implants and devices elsewhere in the body is compared with oral biofilm formation. Biomaterial modifications to discourage biofilm formation on implants and devices are critically discussed for possible applications in dentistry. It is concluded that, for dental applications, antimicrobial coatings killing bacteria upon contact are more promising than antimicrobial-releasing coatings.

  12. Molecular mechanisms of compounds affecting bacterial biofilm formation and dispersal.

    Science.gov (United States)

    Landini, Paolo; Antoniani, Davide; Burgess, J Grant; Nijland, Reindert

    2010-04-01

    Bacteria can switch between planktonic forms (single cells) and biofilms, i.e., bacterial communities growing on solid surfaces and embedded in a matrix of extracellular polymeric substance. Biofilm formation by pathogenic bacteria often results in lower susceptibility to antibiotic treatments and in the development of chronic infections; thus, biofilm formation can be considered an important virulence factor. In recent years, much attention has been directed towards understanding the biology of biofilms and towards searching for inhibitors of biofilm development and of biofilm-related cellular processes. In this report, we review selected examples of target-based screening for anti-biofilm agents: We focus on inhibitors of quorum sensing, possibly the most characterized target for molecules with anti-biofilm activity, and on compounds interfering with the metabolism of the signal molecule cyclic di-GMP metabolism and on inhibitors of DNA and nucleotide biosynthesis, which represent a novel and promising class of biofilm inhibitors. Finally, we discuss the activation of biofilm dispersal as a novel mode of action for anti-biofilm compounds. PMID:20165945

  13. DETECTION OF BIOFILM PRODUCTION IN BLOOD CULTURE ISOLATES OF STAPHYLOCOCCI

    Directory of Open Access Journals (Sweden)

    Gupta Puja, Gupta Pratima, Mittal Garima, Agarwal RK, Goyal Rohit

    2015-01-01

    Full Text Available Background: Biofilm producing bacteria which are inherently resistant to antibiotics and disinfectants are widely associated with implant associated infections. Staphylococcus is the most commonly associated pathogens with bloodstream infection. Aims: The current study was conducted to detect biofilm production in Staphylococci isolated from blood culture specimens. Materials and Methods: 70 clinically significant staphylococcal isolates from blood culture were screened for biofilm production by Tissue culture plate (TCP method, Tube method (TM and Congo red agar (CRA method and their antibiotic susceptibility profile was studied. Results: 59 out of 70 staphylococcal isolates were positive by TCP, out of these 21.4% staphylococci were high biofilm producers, 62.8% staphylococci were moderate biofilm producers and 15.8% were non-biofilm producers. Maximum resistance was observed in biofilm producers to cotrimoxazole (74.5% and erythromycin (62.7% and none were resistant to vancomycin and linezolid. Out of total 59 biofilm producers, 20.3 % (12 were methicillin resistant and all these were S. aureus isolates. 19% (1 out of total 11 biofilm non-producers were methicillin resistant. Conclusion: Biofilm production was seen to be a major virulence factor in most of the staphylococcal isolates obtained from patients with signs and symptoms of septicaemia. S. aureus was found to be the major pathogen and timely detection of biofilm producing phenotype should be carried out using a simple and reproducible method, TCP which is both qualitative and quantitative.

  14. Dexamethason-21-isonicotinat als Begleittherapie bei Kühen mit Systemic Inflammatory Response Syndrome

    OpenAIRE

    Pevec, Till

    2007-01-01

    Dexamethason-21-isonicotinat als Begleittherapie bei Kühen mit Systemic Inflammatory Response Syndrome Schlüsselwörter: Dexamethason, SIRS, Phagozytoseaktivität/Burstaktivität von Monozyten und neutrophilen Granulozyten, Tumornekrose Faktor alpha

  15. Bacteriophages as Weapons Against Bacterial Biofilms in the Food Industry.

    Science.gov (United States)

    Gutiérrez, Diana; Rodríguez-Rubio, Lorena; Martínez, Beatriz; Rodríguez, Ana; García, Pilar

    2016-01-01

    Microbiological contamination in the food industry is often attributed to the presence of biofilms in processing plants. Bacterial biofilms are complex communities of bacteria attached to a surface and surrounded by an extracellular polymeric material. Their extreme resistance to cleaning and disinfecting processes is related to a unique organization, which implies a differential bacterial growth and gene expression inside the biofilm. The impact of biofilms on health, and the economic consequences, has promoted the development of different approaches to control or remove biofilm formation. Recently, successful results in phage therapy have boosted new research in bacteriophages and phage lytic proteins for biofilm eradication. In this regard, this review examines the environmental factors that determine biofilm development in food-processing equipment. In addition, future perspectives for the use of bacteriophage-derived tools as disinfectants are discussed. PMID:27375566

  16. [On Biofilms of Streptomycetes. II. Use in Biotechnology].

    Science.gov (United States)

    Vinogradoya, A; Bulgakova, V G; Polin, A N; Kozhevin, P A

    2015-01-01

    Streptomycetes or mycelial microorganisms are able to form biofilms under the natural, industrial and clinical conditions. The controlled use of biofilms in various industrial processes is much more efficient vs. the cultivation of plankton suspended cells. Optimization of biotechnological processes with the use of streptomycete biofilms is advisable in production of lactic acid and detoxication of the liquor in pyrolysis of plant biomass. Streptomycete biofilms are used in water purification systems. It is recommended to use biofilms for detoxication of wastes and bioremediation of soils contaminated with hard metals. The use of biofilms of streptomycetes producing biologically active substances is of special interest. High yields of.antibiotics and actinomycin D in particular was observed with. cultivation of antibioc-producing streptomycetes as biofilms in bioreactors of unique design.

  17. Bacteriophages as Weapons Against Bacterial Biofilms in the Food Industry.

    Science.gov (United States)

    Gutiérrez, Diana; Rodríguez-Rubio, Lorena; Martínez, Beatriz; Rodríguez, Ana; García, Pilar

    2016-01-01

    Microbiological contamination in the food industry is often attributed to the presence of biofilms in processing plants. Bacterial biofilms are complex communities of bacteria attached to a surface and surrounded by an extracellular polymeric material. Their extreme resistance to cleaning and disinfecting processes is related to a unique organization, which implies a differential bacterial growth and gene expression inside the biofilm. The impact of biofilms on health, and the economic consequences, has promoted the development of different approaches to control or remove biofilm formation. Recently, successful results in phage therapy have boosted new research in bacteriophages and phage lytic proteins for biofilm eradication. In this regard, this review examines the environmental factors that determine biofilm development in food-processing equipment. In addition, future perspectives for the use of bacteriophage-derived tools as disinfectants are discussed.

  18. A limited legacy effect of copper in marine biofilms.

    Science.gov (United States)

    McElroy, David J; Doblin, Martina A; Murphy, Richard J; Hochuli, Dieter F; Coleman, Ross A

    2016-08-15

    The effects of confounding by temporal factors remains understudied in pollution ecology. For example, there is little understanding of how disturbance history affects the development of assemblages. To begin addressing this gap in knowledge, marine biofilms were subjected to temporally-variable regimes of copper exposure and depuration. It was expected that the physical and biological structure of the biofilms would vary in response to copper regime. Biofilms were examined by inductively coupled plasma optical emission spectrometry, chlorophyll-a fluorescence and field spectrometry and it was found that (1) concentrations of copper were higher in those biofilms exposed to copper, (2) concentrations of copper remain high in biofilms after the source of copper is removed, and (3) exposure to and depuration from copper might have comparable effects on the photosynthetic microbial assemblages in biofilms. The persistence of copper in biofilms after depuration reinforces the need for consideration of temporal factors in ecology.

  19. Coexistence facilitates interspecific biofilm formation in complex microbial communities

    DEFF Research Database (Denmark)

    Madsen, Jonas Stenløkke; Røder, Henriette Lyng; Russel, Jakob;

    2016-01-01

    , the underlying role of fundamental ecological factors, specifically coexistence and phylogenetic history, in biofilm formation remains unclear. This study examines how social interactions affect biofilm formation in multi-species co-cultures from five diverse environments. We found prevalence of increased...... biofilm formation among co-cultured bacteria that have coexisted in their original environment. Conversely, when randomly co-culturing bacteria across these five consortia, we found less biofilm induction and a prevalence of biofilm reduction. Reduction in biofilm formation was even more predominant when...... correlated with an increase in planktonic cell numbers, thus implying a behavioral response rather than mere growth competition. Our findings suggest that an increase in biofilm formation is a common adaptive response to long-term coexistence....

  20. Chemoinformatics-assisted development of new anti-biofilm compounds

    DEFF Research Database (Denmark)

    Dürig, Anna; Kouskoumvekaki, Irene; Vejborg, Rebecca Munk;

    2010-01-01

    to identify new and efficient anti-biofilm drugs. We found that ellagic acid (present in green tea) significantly inhibited biofilm formation of Streptococcus dysgalactiae. Based on ellagic acid, we performed in silico screening of the Chinese Natural Product Database to predict a 2nd-generation list...... of compounds with similar characteristics. One of these, esculetin, proved to be more efficient in preventing biofilm formation by Staphylococcus aureus. From esculetin a 3rd-generation list of compounds was predicted. One of them, fisetin, was even better to abolish biofilm formation than the two parent...... compounds. Fisetin dramatically inhibited biofilm formation of both S. aureus and S. dysgalactiae. The compounds did not affect planktonic growth in concentrations where they affected biofilm formation and appeared to be specific antagonists of biofilms. Arguably, since all three compounds are natural...

  1. A limited legacy effect of copper in marine biofilms.

    Science.gov (United States)

    McElroy, David J; Doblin, Martina A; Murphy, Richard J; Hochuli, Dieter F; Coleman, Ross A

    2016-08-15

    The effects of confounding by temporal factors remains understudied in pollution ecology. For example, there is little understanding of how disturbance history affects the development of assemblages. To begin addressing this gap in knowledge, marine biofilms were subjected to temporally-variable regimes of copper exposure and depuration. It was expected that the physical and biological structure of the biofilms would vary in response to copper regime. Biofilms were examined by inductively coupled plasma optical emission spectrometry, chlorophyll-a fluorescence and field spectrometry and it was found that (1) concentrations of copper were higher in those biofilms exposed to copper, (2) concentrations of copper remain high in biofilms after the source of copper is removed, and (3) exposure to and depuration from copper might have comparable effects on the photosynthetic microbial assemblages in biofilms. The persistence of copper in biofilms after depuration reinforces the need for consideration of temporal factors in ecology. PMID:27297593

  2. Effect of Biosynthesized Silver Nanoparticles on Staphylococcus aureus Biofilm Quenching and Prevention of Biofilm Formation

    Institute of Scientific and Technical Information of China (English)

    Pratik R. Chaudhari∗; Shalaka A. Masurkar; Vrishali B. Shidore; Suresh P. Kamble

    2012-01-01

    The development of green experimental processes for the synthesis of nanoparticles is a need in the field of nanotechnology. The synthesis of silver nanoparticles was achieved using Bacillus cereus supernatant and 1 mM silver nitrate. 100 mM glucose was found to quicken the rate of reaction of silver nanoparticles synthesis. UV-visible spectrophotometric analysis was carried out to assess the synthesis of silver nanoparticles. The synthesized silver nanoparticles were further characterized by using Nanoparticle Tracking Analyzer (NTA), Transmission Electron Microscope and Energy Dispersive X-ray spectra. These silver nanoparticles showed enhanced quorum quenching activity against Staphylococcus aureus biofilm and prevention of biofilm formation which can be seen under inverted microscope (40 X). The synergistic effect of silver nanoparticles along with antibiotics in biofilm quenching was found to be effective. In the near future, silver nanoparticles could be used in the treatment of infections caused by highly antibiotic resistant biofilm.

  3. Gene transfer occurs with enhanced efficiency in biofilms and induces enhanced stabilisation of the biofilm structure

    DEFF Research Database (Denmark)

    Molin, Søren; Tolker-Nielsen, Tim

    2003-01-01

    There has been much interest in bioremediation based on the introduction of bacteria able to catabolise recalcitrant compounds deposited in the environment. In particular, the delivery of catabolic information in the form of conjugative plasmids to bacterial populations in situ has great potentia...... cycle and released DNA stabilises the biofilm structure. Both of these gene-transfer mechanisms may be autocatalytically promoted in biofilms, presenting new possibilities for efficient bio-enhancement strategies........ As most bacteria in the environment live in surface-associated communities (biofilms), the gene transfer systems within these communities need to be better characterised for bio-enhancement strategies to be developed. Recent findings suggest that gene transfer does take place within biofilms, but studies...

  4. Modelling of toluene biodegradation and biofilm growth in a fixed biofilm reactor

    DEFF Research Database (Denmark)

    Arcangeli, Jean-Pierre; Arvin, Erik

    1992-01-01

    The modelling of aerobic biodegradation of toluene and the associated biofilm growth in a fixed biofilm system is presented. The model includes four biomass fractions, three dissolved components, and seven processes. It is assumed that part of the active biomass is composed of filamentous bacteria...... which grow relatively fast and detach easily, leading to a biomass growth delayed with respect to substrate degradation. The non-filamentous bacteria inside the biofilm also degrade toluene but with a slower rate compared to the filamentous bacteria. Because the nonfilamentous bacteria do not detach......, they are primarily responsible for the biofilm growth. The active biomass decays into biodegradable and ``inert'' dead biomass which is hydrolyzed into soluble products at two different rates. These products are partly degradable by the biomass and constitute the endogenous respiration. The dynamic growth phase...

  5. A personal history of research on microbial biofilms and biofilm infections

    DEFF Research Database (Denmark)

    Høiby, Niels

    2014-01-01

    80-90 years ago to be important for biofouling on submerged surfaces, e.g. ships. The concept of biofilm infections and their importance in medicine is, however, dental pellicles and my own observations of heaps of Pseudomonas......The observation of aggregated microorganisms surrounded by a self-produced matrix adhering to surfaces or located in tissues or secretions is as old as microbiology, with both Leeuwenhoek and Pasteur describing the phenomenon. In environmental and technical microbiology, biofilms were already shown...... aeruginosa cells in sputum and lung tissue from chronically infected cystic fibrosis patients. The term biofilm was introduced into medicine in 1985 by Costerton. In the following decades, it became obvious that biofilm infections are widespread in medicine, and their importance is now generally accepted....

  6. Microbial biofilms in water-mixed metalworking fluids; Mikrobielle Biofilme in wassergemischten Kuehlschmierstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Thomas [Wisura GmbH, Bremen (Germany)

    2013-05-15

    The microbial load of water-miscible metalworking fluids (MWF) as well as the hygienic aspects and the cost-related impact on the production process due to the activity of microbes is in the focus of many scientific investigations and documented in the related publications. The majority of this research work is focused on the microbiology of the water body, i.e. with the microbial life in the liquid coolant. The habitat biofilm, i.e. the three-dimensional growth of bacteria and fungi on surfaces of the coolant systems has been scarcely considered. Based on the scientific findings made in the recent years studying biofilms it can be concluded, that the relevant microbial processes for the depletion of the MWF and its recontamination takes predominantly places in biofilms. This paper gives an overview of the structure, the formation and the life in biofilms and represents their relevance in MWF systems. (orig.)

  7. Lessons learned from the MIT Tara control and data system

    International Nuclear Information System (INIS)

    The control and data system of the MIT Tara Tandem Mirror has worked successfully throughout the lifetime of the experiment (1983 through 1987). As the Tara project winds down, it is appropriate to summarize the lessons learned from the implementation and operation of the control and data system over the years and in its final form. The control system handled ∼2400 I/0 points in real time throughout the 5 to 10 minute shot cycle while the data system, in near real time, handled ∼1000 signals with a total of 5 to 7 Mbytes of data each shot. The implementation depended upon a consistent approach based on separating physics and engineering functions and on detailed functional diagrams with narrowly defined cross communication. This paper is a comprehensive treatment of the principal successes, residual problems, and dilemmas that arose from the beginning until the final hardware and software implementation. Suggestions for future systems of either similar size or of larger scale such as CIT are made in the conclusion. 11 refs., 1 fig

  8. Diagnostische und therapeutische Optionen bei Patientinnen mit Myomen: Myomembolisation

    Directory of Open Access Journals (Sweden)

    Bohlmann MK

    2014-01-01

    Full Text Available iHintergrund:/i Symptomatische Uterusmyome stellen einen häufigen und bedeutsamen Morbiditätsgrund für Frauen in der reproduktiven Lebensphase dar. Aufgrund bis dato eingeschränkter konservativer Therapieoptionen erfolgten zur Symptomkontrolle operative Interventionen, wobei in einem hohen Prozentsatz Hysterektomien erfolgten. Mit der Methode der kathetergestützten Myomembolisation steht seit einiger Zeit eine nicht-invasive Alternative zur Myombehandlung zur Verfügung. iMethoden:/i Im Rahmen dieser Übersicht werden Indikationen, Voraussetzungen, Durchführung, Nebenwirkungen und Outcome einer Embolisationsbehandlung dargestellt, wobei insbesondere auf fertilitätsrelevante Aspekte eingegangen wird. iErgebnis:/i Die Therapieform der Embolisation weist gute Erfolgsraten in Bezug auf eine Verbesserung der Hypermenorrhoe (etwa 85 % der Versuche auf, wohingegen myombedingte Verdrängungs- und Druckbeschwerden zu 30–60 % erfolgreich behandelt werden. Die ischämiebedingten Beschwerden im Rahmen einer Intervention bedürfen einer adäquaten Analgesie. iSchlussfolgerung:/i Die Behandlung mittels Embolisation kann in ausgewählten Fällen eine effektive und nicht-invasive Therapieoption bei symptomatischem Uterus myomatosus darstellen.

  9. Echtzeit-Ultraschallsimulation auf Grafik-Prozessoren mit CUDA

    Science.gov (United States)

    Reichl, Tobias; Passenger, Josh; Acosta, Oscar; Salvado, Olivier

    Trotz der zunehmenden Verbreitung jüngerer bildgebender Verfahren bleibt medizinischer Ultraschall (US) weiterhin ein wichtiges Hilfsmittel bei chirurgischen Eingriffen und der klinischen Diagnose. Viele US-gestützte medizinische Prozeduren erfordern allerdings ausgiebiges Training, so dass es wünschenswert ist, eine realistische Simulation von US-Bildern zur Verfügung zu stellen. Im Gegensatz zu früheren Ansätzen simulieren wir solche Bilder auf der "Graphics Processing Unit“. Wir erweitern hierzu eine Methode, die von Wein et al. für die Abschätzung von US-Reflexionen aus Daten der Computertomographie (CT) vorgeschlagen wurde, zu einer leichter zu berechnenden Form. Zusätzlich schätzen wir die US-Absorption aus den CT-Daten ab. Mit Hilfe von NVIDIAs "Compute Unified Device Architecture“ (CUDA) simulieren wir Reflexion, Verschattung, Rauschen und radiale Unschärfe, ausgehend von unbearbeiteten CT-Daten in Echtzeit und ohne Vorausberechnung.

  10. Quellverhalten teilgesättigter bindiger Böden mit mittlerem Quellpotential

    OpenAIRE

    Dobrowolsky, Markus

    2008-01-01

    Die Arbeit beschäftigt sich mit der Bestimmung der Zwangsbeanspruchungen und mit den daraus resultierenden Verformungen auf geotechnische Bauwerke infolge Quellen von teilgesättigten, bindigen Böden. Zur Ermittlung eines Quellgesetzes zur Beschreibung dieses Volumenänderungsverhaltens wurden zwei spezielle Oedometergeräte entwickelt. Mittels eines modifizierten Oedometers können radiale und axiale Quelldrücke getrennt voneinander gemessen sowie axiale Dehnungen zugelassen werden. Die axialen ...

  11. Spätfolgen nach Stimmlippenaugmentation mit Teflon: Klinisches Bild und Rehabilitation

    OpenAIRE

    Reiter, R.; J. Veit; Brosch, S

    2012-01-01

    Hintergrund: Teflon wurde vor allem bis etwa 1990 zur Stimmlippenaugmentation bei einer einseitigen Stimmlippenparese eingesetzt. Aufgrund mehrerer Beobachtungen von Teflongranulomen bzw. Dislokation in Zusammenhang mit der Applikation im Larynx gilt die Substanz inzwischen als obsolet.Material und Methoden: Wir beschreiben mögliche Komplikationen, deren Diagnostik und Therapie bei 2 Patienten mit vorangegangener permanenter Stimmlippenaugmentation mittels Teflon.Ergebnisse: Ein 61-jährige...

  12. Interaktion von Betonstahl und textiler Bewehrung bei der Biegeverstärkung mit textilbewehrtem Beton

    OpenAIRE

    Weiland, Silvio

    2010-01-01

    Textilbewehrter Beton zur Verstärkung von Stahlbetonbauteilen ist neben den klassischen und etablierten Verfahren eine äußerst interessante Alternative, die die Vorteile der leichten Kohlenstofffaserklebeverstärkungen mit denen von Spritzbeton mit Bewehrung verbindet. Aus den theoretischen und experimentellen Untersuchungen in dieser Arbeit können wichtige Erkenntnisse zum gemeinsamen Tragverhalten von Betonstahl und textiler Bewehrung sowie zu den Auswirkungen der verbundbedingten Unterschie...

  13. Untersuchungen zum Zugtragverhalten hochduktiler Faserbetone mit zusätzlicher Textilbewehrung

    OpenAIRE

    Korb, Simone

    2010-01-01

    Hochduktiler Faserbeton zeigt ein dehnungsverfestigendes Zugtragverhalten mit ausgeprägter Vielfachrissbildung und einer Bruchdehnung von bis zu 5 %. Aufgrund der sehr kleinen Rissbreiten im Gebrauchszustand von weniger als 0,1 mm können hochduktile Faserbetone als quasi-wasserundurchlässig angesehen werden. Ausgehend von diesen Materialeigenschaften entstand die Überlegung, Fugen, z.B. zwischen Betonfertigteilen im Hochbau, mit einer Abdeckung aus hochduktilem Faserbeton zu überbrücken. Hier...

  14. Asymptotische Nahfeldanalysen ebener Multi-Materialverbindungsstellen mit der Methode komplexer Potentiale

    OpenAIRE

    Sator, Christian

    2010-01-01

    In der vorliegenden Arbeit werden die Nahfelder an ebenen Multi-Materialverbindungsstellen betrachtet, die aus Fügungen isotroper Sektoren bestehen und ausschließlich in ihrer Ebene belastet sind. Die asymptotischen Nahfeldanalysen erfolgen mit der Methode komplexer Potentiale mit einer geeigneten Kombination von Potenzfunktionen. Bei den Analysen steht insbesondere die Ermittlung der Singularitätsexponenten im Vordergrund. Die Arbeit leistet einige neue theoretische Beiträge: So wird ein Nac...

  15. Untersuchung innermotorischer Einflussgrößen auf die Partikelemission eines Ottomotors mit Direkteinspritzung

    OpenAIRE

    Dageförde, Helge

    2015-01-01

    Die Arbeit befasst sich mit der Ermittlung der Ursachen von Partikelemissionen und der Ableitung von Maßnahmen zu ihrer Reduktion. Dabei spielt die Betrachtung der Gemischbildung eine wesentliche Rolle. Es werden innermotorische optische Untersuchungen an einem Einhubtriebwerk sowie einem Einzylindermotor durchgeführt und mehrere Faktoren auf ihren Einfluss auf die Partikelbildung und -oxidation diskutiert. Die motorischen Untersuchungen werden mit Partikelmessungen im Abgas begleitet.

  16. Nichtinvasive Messung von Blutparameter mit Infrarot-Quantenkaskadenlaser und photoakustischer Detektion

    OpenAIRE

    Xhelaj, Arjan

    2009-01-01

    Diese Arbeit beschreibt wie mit physikalischen Methoden die Glukosekonzentration gemessen werden kann. Die Infrarot-Spektroskopie bietet eine Möglichkeit da die Energie der meisten Molekülschwingungen Photonenenergien im infraroten Spektralbereich entspricht. Hier zeigen Glukosemoleküle charakteristische Absorptionsspektren, die mit spektroskopischen Methoden gemessen werden. Um nicht invasiv zu messen, wurde eine photoakustische Messmethode gewählt. Die Grundidee ist, dass die durch Licht an...

  17. Untersuchung einer Axialgitterschaufel mit Höchstumlenkung durch Struktur- und niederfrequente Wölbungsvariation

    OpenAIRE

    Jarius, Marc

    2000-01-01

    In hydraulischen und thermischen Strömungsmaschinen werden zur Erzeugung eines Vordralls Vorleiträder mit Schaufeln variabler Staffelung eingesetzt. Diese Vorleiträder besitzen nur bei relativ kleinen Umlenkwinkeln relativ kleine Verluste und finden ihre Anwendung hauptsächlich in großen Kraftwerks-Kühl- wasserpumpen. Dieses Regelverfahren wird sowohl bei halbaxialen als auch bei axialen Kreiselpumpen eingesetzt. In diesem Projekt soll die Umströmung einer einzelnen Vorleitradschaufel mit var...

  18. Die "wîlsælde"-Disputation : zur Auseinandersetzung mit der Astrologie in der "Kaiserchronik"

    OpenAIRE

    Dunphy, Graeme

    2011-01-01

    Als Einschub in der mittelhochdeutschen "Kaiserchronik" bieten die drei Disputationen weitaus tiefer greifende philosophisch-theologische Betrachtungen als der übrige Erzähltext. Die "wîlsælde"-Disputation greift die Auseinandersetzung mit der Astrologie auf. Der vorliegende Aufsatz vergleicht dieses Streitgespräch mit seiner patristischen Vorlage, den pseudoklementinischen "Recognitiones", und erkäirt die Umgestaltung des Stoffes in der "Kaiserchronik" im Hinblick auf Unterschiede in den ast...

  19. Vorkommen von Bakterien im unteren Respirationstrakt und deren Antibiotikaresistenz bei Hunden mit respiratorischen Symptomen

    OpenAIRE

    Rheinwald, Markus

    2015-01-01

    Im Rahmen der vorliegenden Arbeit wurde das Vorkommen von Bakterien im unteren Respirationstrakt von Hunden mit Atemwegserkrankungen und deren Resistenzverhalten gegenüber klinisch relevanten Antibiotika untersucht. Hierfür wurden die Ergebnisse der bakteriologischen Untersuchungen und Resistenztests von 502 Proben von 493 Hunden retrospektiv ausgewertet, die im Zeitraum von 1989 bis 2011 an der Medizinischen Kleintierklinik der Ludwig-Maximilians-Universität München mit respiratorischen Symp...

  20. Amifostin in subkutaner Anwendung bei Patienten mit Kopf-Hals-Tumoren

    OpenAIRE

    Wilder, Daniel

    2006-01-01

    Hintergrund: Amifostin (Ethyol®), ein phosphorylierter Aminothioalkohol mit der chemischen Bezeichnung S-2[3-aminopropylamino]-ethyl-thiophosphorsäure, ist eine Substanz mit einem breiten zytoprotektiven Spektrum für die radio- und chemotherapeutisch induzierten Nebenwirkungen. Die Substanz fungiert dabei im Sinne einer Prodrug. Daraus wird, in Abhängigkeit von der alkalischen Phosphatase, der dephosphorylierte aktive Metaboliten WR-1065 gebildet. Dieser ist für die protektiven Wirkungen ...

  1. Entwicklung und Evaluation eines psychoedukativen Elterngruppen-Trainingsprogramms für Familien mit autistischen Kindern

    OpenAIRE

    Probst, Paul

    2003-01-01

    In der Einleitung wird das Konzept des "Psychoedukativen Elterntrainings" erläutert und ein Überblick über den Forschungsstand zum Thema "Elterntraining in Familien mit autistischen Kindern" gegeben. Ausgehend von dieser Analyse wurde ein psychoedukatives Eltern-Gruppentraining für Familien mit autistischen Kindern entwickelt und im Rahmen eines 3-Monate-Follow-up-Versuchsplans evaluiert. Die beiden Hauptziele des Trainingcurriculums waren "Vermittlung eines Konzepts über Wesen, Ursach...

  2. Entwicklung und Evaluation eines psychoedukativen Elterngruppen-Trainingsprogramms für Familien mit autistischen Kindern

    OpenAIRE

    Probst, Paul

    2003-01-01

    In der Einleitung wird das Konzept des „Psychoedukativen Elterntrainings“ erläutert und ein Überblick über den Forschungsstand zum Thema „Elterntraining in Familien mit autistischen Kindern“ gegeben. Ausgehend von dieser Analyse wurde ein psychoedukatives Eltern-Gruppentraining für Familien mit autistischen Kindern entwickelt und im Rahmen eines 3-Monate-Follow-up-Versuchsplans evaluiert. Die beiden Hauptziele des Trainingcurriculums waren „Vermittlung eines Konzepts über Wesen, Ursachen, Beh...

  3. Dieselmotorische Kraftstoffzerstäubung und Gemischbildung mit Common-Rail Einspritzsystemen

    OpenAIRE

    Ofner, Bernd

    2014-01-01

    Mit der PDA-Messtechnik sowie mit dem Mie-Streulicht- und dem Schlieren-/Schattenverfahren wurden die dieselmotorische Kraftstoffzerstäubung und Gemischbildung in Druckkammern und in einer schnellen Kompressionsmaschine untersucht. Die Arbeiten konzentrierten sich auf die zeitliche Strahlausbreitung, den Kegelwinkel, das Tropfenspektrum und die Sprayverdampfung, abhängig von Gasdichte, Einspritzdruck und Gastemperatur. Drosseleffekte am Nadelsitz können die Spraybildung stark beeinflussen, wo...

  4. Analyse und Bewertung von Parametern der Produktionsumwelt bei der Milchgewinnung mit automatischen Melksystemen (AMS)

    OpenAIRE

    Unrath, Jens

    2005-01-01

    Automatische Melksysteme (AMS) gelten als jüngste Innovation auf dem Gebiet der Melktechnik und weisen im Vergleich mit konventionellen Melkständen eine Reihe von Besonderheiten auf. Um die Kühe zum freiwilligen und regelmäßigen Besuch des Melksystems anzuhalten, sind optimale mikroklimatische Bedingungen in der Melkbox notwendig. Die Analyse der mikroklimatischen Bedingungen in AMS erfolgte in einem Betrieb mit zwei parallel arbeitenden AMS und 110 melkenden Kühen. Dabei wurden die Parameter...

  5. Sandwichelemente mit Deckschichten aus Hochleistungsbeton und einem Kern aus extrudiertem Polystyrol

    OpenAIRE

    Müller, Frank

    2015-01-01

    Sandwichelemente vereinen aufgrund des gezielten Einsatzes verschiedener Materialien und deren schichtartigen Aufbaus sehr gute Dämmeigenschaften und ein geringes Eigengewicht mit hoher Tragfähigkeit und Biegesteifigkeit. Sie werden daher seit Beginn der 1960er-Jahre sowohl im Metallleichtbau als auch im Stahlbetonmassivbau vielfältig eingesetzt. Im Rahmen der vorliegenden Arbeit wurden Sandwichelemente mit Deckschichten aus einem mikro- oder auch textilbewehrtem Hochleistungsbeton und einem ...

  6. Kognitive Dysphasie und Angst : linguistische Untersuchungen bei Patienten mit Epilepsie und Angsterkrankung

    OpenAIRE

    Schneider, Barbara

    2007-01-01

    In der vorliegenden Arbeit wird der Frage nachgegangen, wie sich hirnorganische Erkrankungen, die nicht die klassischen perisylvischen Sprachareale betreffen, auf sprachliche und sprachorganisierende Funktionen auswirken. Dazu wurde eine Gruppe von Patienten mit fokaler Epilepsie und Angstaura (n = 8) sowie eine Gruppe von Patienten mit Angsterkrankung (n = 8) linguistisch untersucht. Ziel war es zum einen, Kognitive Dysphasien als sekundäre Sprach- bzw. Kommunikationsstörungen infolge kognit...

  7. Bestimmung der Ionisationsenergie von Actinium und Ultraspurenanalyse von Plutonium mit resonanter Ionisationsmassenspektrometrie (RIMS)

    OpenAIRE

    Waldek, Achim Marcus

    2001-01-01

    ZusammenfassungDie Resonanzionisationsmassenspektrometrie (RIMS) verbindet hohe Elementselektivität mit guter Nachweiseffizienz. Aufgrund dieser Eigenschaften ist die Methode für Ultraspurenanalyse und Untersuchungen an seltenen oder schwer handhabbaren Elementen gut geeignet. Für RIMS werden neutrale Atome mit monochromatischem Laserlicht ein- oder mehrfach resonant auf energetisch hoch liegende Niveaus angeregt und anschließend durch einen weiteren Laserstrahl oder durch ein elektrisches Fe...

  8. Ziehen von Rohren aus Aluminiumlegierungen über einem Pendelziehdorn mit Ultraschall

    OpenAIRE

    Klubovic, Vladimir V.; Komlik, L. K.; Chrenov, O. V.

    1994-01-01

    Unter Einkopplung von longitudinalen Ultraschallschwingungen kann man beim Rohrziehen aus Aluminiumlegierungen über einem Pendelziehdorn die Ziehkraft um 25 - 32 % senken und gleichzeitig die logarithmische Formänderung beim Ziehen pro Durchgang steigern. Das Rohrziehen mit Ultraschall über einem fliegenden Dorn ist effektiver als das Vollprofilziehen. Die Anwendung von Ultraschallschwingungen mit großer Intensität ist eine notwendige Bedingung für eine effektive Senkung der Ziehkraft, besond...

  9. Abbildungsmethoden für die Brust mit einem 3D-Ultraschall-Computertomographen

    OpenAIRE

    Dapp, Robin

    2013-01-01

    In dieser Arbeit wird die Theorie, Implementierung und Evaluierung von Algorithmen der Ultraschall-Transmissionstomographie für den am KIT entwickelten Prototypen 3D-USCT II behandelt. Bisherige Arbeiten gehen von idealen Voraussetzungen aus, diese Arbeit befasst sich hingegen mit der Bildrekonstruktion rauschbehafteter Echtdaten, die in einer klinischen Pilotstudie aufgenommen wurden. Von drei Krebsfällen konnten mit den Methoden dieser Arbeit zwei eindeutig identifiziert werden.

  10. Einfluss von Nickel auf Herstellung und Eigenschaften von bainitischem Gusseisen mit Kugelgraphit

    OpenAIRE

    Moualla, Hadi

    2009-01-01

    Gerade in Hinblick auf die Kombination aus hervorragender Festigkeit, relativ guter Zähigkeit und Dauerfestigkeit sowie beachtlicher Verschleißbeständigkeit macht bainitisches Gusseisen mit Kugelgrafit und dabei besonders das ADI (Austempered Duktile Iron) durch sein ausferritisches Gefüge seine Vorteile gegenüber Gusseisenwerkstoffen insbesondere Gusseisen mit Kugelgraphit und auch Stahlguss deutlich. Die konventionelle Herstellung von ADI erfolgt über ein Austenitisieren und ein anschließen...

  11. Höchstfeste nichtrostende austenitische CrMn-Stähle mit (C+N)

    OpenAIRE

    Riedner, Sascha

    2010-01-01

    Nichtrostende austenitische Stähle erzielen in der Regel nur geringe Festigkeiten. Die effektivste Methode zur Festigkeitssteigerung bietet das Legieren mit interstitiellen Atomen. Das gemeinsame Legieren mit (C+N) resultiert in offen erschmelzbaren, hochfesten nichtrostenden Austentiten. Die neuentwickelten Stähle weisen eine sehr hohe Austenitstabilität, Festigkeit, Kaltverfestigung, Zähigkeit und Duktilität auf. Auch unter zyklischer Beanspruchung kann die hohe Festigkeit genut...

  12. Untersuchungen an neutronenbestrahlten Reaktordruckbehälterstählen mit Neutronen-Kleinwinkelstreuung

    OpenAIRE

    Ulbricht, Andreas

    2010-01-01

    In dieser Arbeit wurde die durch Bestrahlung mit schnellen Neutronen bedingte Materialalterung von Reaktordruckbehälterstählen untersucht. Das Probenmaterial umfasste unbestrahlte, bestrahlte und ausgeheilte RDB-Stähle russischer und westlicher Reaktoren sowie Eisenbasis-Modelllegierungen. Mittels Neutronen-Kleinwinkelstreuung ließen sich bestrahlungsinduzierte Leerstellen/Fremdatom-Cluster unterschiedlicher Zusammensetzung mit mittlerem Radius um 1.0 nm nachweisen. Ihr Volumenanteil steigt m...

  13. Vorblütebehandlungen mit Kaolin gegen den Gemeinen Birnenblattsauger (Cacopsylla pyri)

    OpenAIRE

    Daniel, Claudia; Wyss, Eric

    2008-01-01

    Der Gemeine Birnenblattsauger, Cacopsylla pyri (L.) (Homoptera: Psyllidae), ist ein wichtiger Schädling in der Birnenproduktion. Ende Februar beginnen die überwinternden Adulten mit der Eiablage. Zu Schäden, wie Ertragsverlusten und Fruchtverschmutzungen durch Honigtau, kommt es jedoch erst durch die zahlreichen Nymphen der dritten Generation. Die Bekämpfung erfolgt meist mit Insektizidbehandlungen gegen die Nymphen der ersten drei Generationen (BOVEY et al. 1979). Im ökologischen Anbau wird ...

  14. Laccase-katalysierte Dominoreaktionen von Brenzcatechinen und Hydrochinonen mit 1,3-Dicarbonylverbindungen

    OpenAIRE

    Hajdok, Szilvia

    2012-01-01

    In der vorliegenden Arbeit wurden neuartige Dominoreaktionen beschrieben, die auf Laccase-katalysierten Oxidation von Brenzcatechinen und Hydrochinonen zu den entsprechenden o- und p-Chinonen und sich daran anschließenden Umsetzungen mit 1,3-Dicarbonylen beruhen. Im ersten Teil dieser Dissertation wurde ein effizienter Zugang zu 3,4-Dihydro-7,8-dihydroxy-2H-dibenzofuran-1-onen entwickelt, der sich die Laccase-initiierte Dominoreaktion zwischen Cyclohexan-1,3-dionen und Brenzcatechinen mit...

  15. eine randomisierte Studie an 200 Patienten mit Prostatae kleiner 100 g und urodynamisch nachgewiesener Obstruktion

    OpenAIRE

    Ahyai, Sascha A.

    2006-01-01

    Ziele: Trotz ihrer signifikanten Morbidität stellt die transurethrale Resektion der Prostata (TURP) den gold standard dar für die instrumentelle Therapie der durch die benigne Prostatahyperplasie (BPH) bedingten Blasenauslassobstruktion. Mit dem Hochleistungs-Holmium: YAG Laser kann endoskopisch, in einer relativ blutungsarmen Weise, Prostatagewebe enukleiert werden. Wir verglichen die Technik der transurethralen Holmium-Laser-Enukleation der Prostata (HoLEP) mit der Standard-TURP bei der ope...

  16. Serologischer Verlauf bei einer Infektion mit T. pallidum innerhalb einer Hochrisikopopulation in Tansania, Ostafrika

    OpenAIRE

    Dechamps, Britta

    2005-01-01

    Diese Doktorarbeit entstand im Rahmen eines HIV-Projekt des Tropeninstitutes München in Tansania. Dabei wurden die serologischen Daten bei einer Infektion mit Syphilis innerhalb einer Gruppe von 600 Prostituierten ausgewertet. Das Problem des serologischen Nachweises von Syphilis ist, dass die verschiedenen Testverfahren nur jeweilig begrenzte Aussagekraft bezüglich Stadium und Aktivität der Krankheit haben. Das Ziel meiner Arbeit war daher, herauszufinden, ob mit den Informationen von Ig...

  17. Biomechanische Untersuchungsergebnisse über die verbesserte Verankerung von Pedikelschrauben mit resorbierbarem

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Die Prim?rstabilit?t von Pedikelschrauben im Knochen h?ngt in hohem Masse von der Knochendichte ab. Die Augmentation mit Zement ist ein klinisch einsetzbares Verfahren, um die Schrauben-Verankerung im osteoporotischen Knochen zu verbessern.In dieser Studie wurde eine neuartiges resorbierbares Knochenersatzmaterial (α-BSMTM) für diese Augmentation benutzt. Biomechanische Testungen wurden in vitro bei 16 Lendwirbelkorpern (L3-L5) aus 6 Individuen(75,2±13,7 Jahre) durchgeführt. Vor der biomechanischen Testung wurde bei allen Pr?paraten die trabekul?re Knochendichte mittels pQCT gemessen und beide Pedikel mit USS-Pedikelschrauben (5,0 mm × 45 mm) besetzt, von welchen eine mit α-BSMTM augmentiert war. Beim axialen Auszugstest wurden die maximale axiale Auszugskraft (F-max) sowie die Energieaufnahme bestimmt. Der Medianwert der F-max stieg beim Auszugstest durch die Zementierung mit α-BSMTM um 80 % von 370 N (ohne Zement) auf 665 N (mit Zement). Die Energieaufnahme bis zum Erreichen der F-max (E-F-max) und bei Dislokation bis 2,0 mm (E-2 mm) steigerte sich ebenfalls um 83 % und 68 %. Die Unterschiede waren signifikant. (Wilcoxon′s-Test, P<0,01) Die Ausreisskrafte F-max (ohne oder mit Zement) korrelierten eng mit der Knochendichte (r=0,9056 und r=0,9585). Unsere Resultate zeigen, da eine Augmentation mit dem α-BSMTM die prim?re Stabilit?t von Pedikelschrauben verbessern kann. Der Effekt scheint auf einer Optimierung der Kontaktfl?che und einer Aussteifung der schraubennahen Spongiosa zu beruhen. Das Material konnte geeignet sein, die Verankerung von Pedikelschrauben bei osteoporotischen Patieten zu verbessern.

  18. Biofilm-based central line-associated bloodstream infections.

    Science.gov (United States)

    Yousif, Ammar; Jamal, Mohamed A; Raad, Issam

    2015-01-01

    Different types of central venous catheters (CVCs) have been used in clinical practice to improve the quality of life of chronically and critically ill patients. Unfortunately, indwelling devices are usually associated with microbial biofilms and eventually lead to catheter-related bloodstream infections (CLABSIs).An estimated 250,000-400,000 CLABSIs occur every year in the United States, at a rate of 1.5 per 1,000 CVC days and a mortality rate of 12-25 %. The annual cost of caring for patients with CLABSIs ranges from 296 million to 2.3 billion dollars.Biofilm formation occurs on biotic and abiotic surfaces in the clinical setting. Extensive studies have been conducted to understand biofilm formation, including different biofilm developmental stages, biofilm matrix compositions, quorum-sensing regulated biofilm formation, biofilm dispersal (and its clinical implications), and multi-species biofilms that are relevant to polymicrobial infections.When microbes form a matured biofilm within human hosts through medical devices such as CVCs, the infection becomes resistant to antibiotic treatment and can develop into a chronic condition. For that reason, many techniques have been used to prevent the formation of biofilm by targeting different stages of biofilm maturation. Other methods have been used to diagnose and treat established cases of CLABSI.Catheter removal is the conventional management of catheter associated bacteremia; however, the procedure itself carries a relatively high risk of mechanical complications. Salvaging the catheter can help to minimize these complications.In this article, we provide an overview of microbial biofilm formation; describe the involvement of various genetic determinants, adhesion proteins, organelles, mechanism(s) of biofilm formation, polymicrobial infections, and biofilm-associated infections on indwelling intravascular catheters; and describe the diagnosis, management, and prevention of catheter-related bloodstream infections

  19. Planktonic versus Biofilm Catabolic Communities: Importance of the Biofilm for Species Selection and Pesticide Degradation

    OpenAIRE

    Verhagen, Pieter; De Gelder, Leen; Hoefman, Sven; De Vos, Paul; Boon, Nico

    2011-01-01

    Chloropropham-degrading cultures were obtained from sludge and soil samples by using two different enrichment techniques: (i) planktonic enrichments in shaken liquid medium and (ii) biofilm enrichments on two types of solid matrixes (plastic chips and gravel). Denaturing gradient gel electrophoresis fingerprinting showed that planktonic and biofilm cultures had a different community composition depending on the presence and type of added solid matrix during enrichment. This was reflected in t...

  20. Hydrophobicity of biofilm coatings influences the transport dynamics of polystyrene nanoparticles in biofilm-coated sand.

    Science.gov (United States)

    Mitzel, Michael R; Sand, Stefanie; Whalen, Joann K; Tufenkji, Nathalie

    2016-04-01

    Engineered nanoparticles (ENPs) are used in the manufacture of over 2000 industrial and consumer products to enhance their material properties and functions or to enable new nanoparticle-dependent functions. The widespread use of ENPs will result in their release to the subsurface and aquatic environments, where they will interact with indigenous biota. Laboratory column experiments were designed to understand the influence of two different Pseudomonas aeruginosa biofilms on the mobility of polystyrene latex nanoparticles in granular porous media representative of groundwater aquifers or riverbank filtration settings. The transport behavior of 20 nm carboxylate-modified (CLPs) and sulfate (SLPs) polystyrene latex ENPs suspended in NaCl or CaCl2 (1 and 10 mM ionic strength, pH 7) was studied in columns packed with quartz sand coated with biofilms formed by two P. aeruginosa strains that differed in cell surface hydrophobicity (P. aeruginosa 9027™, relatively hydrophilic and P. aeruginosa PAO1, relatively hydrophobic). Biofilm-coated quartz sand retained more of the electrostatically-stabilized latex ENPs than clean, uncoated sand, regardless of the serotype. As IS increased, clear differences in the shape of the ENP breakthrough curves were observed for each type of biofilm coating. ENP breakthrough in the P. aeruginosa PAO1 biofilm-coated sand was generally constant with time whereby breakthrough in the P. aeruginosa 9027 biofilm-coated sand showed dynamic behavior. This indicates a fundamental difference in the mechanisms of ENP deposition onto hydrophilic or hydrophobic biofilm coatings due to the hydration properties of these biofilms. The results of this study demonstrate the importance of considering the surface properties of aquifer grain coatings when evaluating ENP fate in natural subsurface environments. PMID:26845456