TY - THES A1 - Sarlet, Adrien T1 - Tuning the viscoelasticity of Escherichia coli biofilms T1 - Abstimmung der Viskoelastizität von Escherichia coli-Biofilmen BT - interplay between extrinsic and intrinsic factors BT - Wechselspiel zwischen extrinsischen und intrinsischen Faktoren N2 - Biofilms are heterogeneous structures made of microorganisms embedded in a self-secreted extracellular matrix. Recently, biofilms have been studied as sustainable living materials with a focus on the tuning of their mechanical properties. One way of doing so is to use metal ions. In particular biofilms have been shown to stiffen in presence of some metal cations and to soften in presence of others. However, the specificity and the determinants of those interactions vary between species. While Escherichia coli is a widely studied model organism, little is known concerning the response of its biofilms to metal ions. In this work, we aimed at tuning the mechanics of E. coli biofilms by acting on the interplay between matrix composition and metal cations. To do so, we worked with E. coli strains producing a matrix composed of curli amyloid fibres or phosphoethanolamine-cellulose (pEtN-cellulose) fibres or both. The viscoelastic behaviour of the resulting biofilms was investigated with rheology after incubation with one of the following metal ion solutions: FeCl3, AlCl3, ZnCl2 and CaCl2 or ultrapure water. We observed that the strain producing both fibres stiffen by a factor of two when exposed to the trivalent metal cations Al(III) and Fe(III) while no such response is observed for the bivalent cations Zn(II) and Ca(II). Strains producing only one matrix component did not show any stiffening in response to either cation, but even a small softening. In order to investigate further the contribution of each matrix component to the mechanical properties, we introduced additional bacterial strains producing curli fibres in combination with non-modified cellulose, non-modified cellulose only or neither component. We measured biofilms produced by those different strains with rheology and without any solution. Since rheology does not preserve the architecture of the matrix, we compared those results to the mechanical properties of biofilms probed with the non-destructive microindentation. The microindentation results showed that biofilm stiffness is mainly determined by the presence of curli amyloid fibres in the matrix. However, this clear distinction between biofilm matrices containing or not containing curli is absent from the rheology results, i.e. following partial destruction of the matrix architecture. In addition, rheology also indicated a negative impact of curli on biofilm yield stress and flow stress. This suggests that curli fibres are more brittle and therefore more affected by the mechanical treatments. Finally, to examine the molecular interactions between the biofilms and the metal cations, we used Attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) to study the three E.coli strains producing a matrix composed of curli amyloid fibres, pEtN-cellulose fibres or both. We measured biofilms produced by those strains in presence of each of the aforementioned metal cation solutions or ultrapure water. We showed that the three strains cannot be distinguished based on their FTIR spectra and that metal cations seem to have a non-specific effect on bacterial membranes in absence of pEtN-cellulose. We subsequently conducted similar experiments on purified curli or pEtN-cellulose fibres. The spectra of the pEtN-cellulose fibres revealed a non-valence-specific interaction between metal cations and the phosphate of the pEtN-modification. Altogether, these results demonstrate that the mechanical properties of E. coli biofilms can be tuned via incubation with metal ions. While the mechanism involving curli fibres remains to be determined, metal cations seem to adsorb onto pEtN-cellulose and this is not valence-specific. This work also underlines the importance of matrix architecture to biofilm mechanics and emphasises the specificity of each matrix composition. N2 - Biofilme sind heterogene Strukturen aus Mikroorganismen, die in eine selbst-abgesonderte extrazelluläre Matrix eingebettet sind. In letzter Zeit wurden Biofilme als nachhaltige lebende Materialien untersucht, mit dem Ziel ihre mechanischen Eigenschaften zu modifizieren. Eine Möglichkeit, dies zu tun, ist die Verwendung von Metallionen. Es hat sich gezeigt, dass Biofilme in Gegenwart einiger Metallkationen steifer und in Gegenwart anderer weicher werden. Die Spezifität und die Bestimmungsfaktoren dieser Wechselwirkungen sind jedoch je nach Spezies unterschiedlich. Obwohl Escherichia coli ein weithin untersuchter Modellorganismus ist, ist wenig über den Einfluss von Metallionen auf die Eigenschaften von E. coli-Biofilmen bekannt. Ziel dieser Arbeit war, die mechanischen Eigenschaften von E. coli-Biofilmen durch Beeinflussung des Zusammenspiels von Matrixzusammensetzung und Metallkationen zu untersuchen und zu verändern. Zu diesem Zweck wurden E. coli-Stämme verwendet, die eine Matrix aus Curli-Fasern oder Phosphoethanolamin-modifizierter Zellulose (pEtN-Zellulose) oder aus beiden produzieren. Das viskoelastische Verhalten der resultierenden Biofilme wurde nach Inkubation mit einer der folgenden Metallsalzlösungen (oder Reinstwasser) rheologisch untersucht: FeCl3, AlCl3, ZnCl2 und CaCl2. Es zeigte sich, dass die Steifigkeit von Biofilmen des Stammes, der beide Fasern produziert, um das Doppelte höher ist, wenn sie den dreiwertigen Metallkationen Al(III) und Fe(III) ausgesetzt werden. Im Gegensatz dazu konnte keine derartige Veränderung der Steifigkeit beobachtet werden, wenn stattdessen die zweiwertigen Kationen Zn(II) und Ca(II) zugesetzt wurden. Stämme, die nur eine Matrixkomponente produzieren, zeigten keine Versteifung in Gegenwart von Kationen, sondern sogar eine geringe Erweichung. Um den Beitrag der einzelnen Matrixkomponenten zu den mechanischen Eigenschaften weiter zu untersuchen, wurden weitere Bakterienstämme mit den bereits genannten verglichen. Diese Stämme produzieren entweder Curli-Fasern in Kombination mit nicht modifizierter Zellulose, ausschließlich nicht modifizierte Zellulose oder keine der beiden Komponenten. Die resultierenden Biofilme wurden ohne den Zusatz von Salzlösung rheologisch charakterisiert. Da die Matrixarchitektur bei Rheologiemessungen zerstört wird, wurden die Biofilme ebenfalls mit Mikroindentation untersucht, welche mit intakten Biofilmen durchgeführt werden kann. Die Ergebnisse der Mikroindentation zeigen, dass die Steifigkeit der Biofilme hauptsächlich durch das Vorhandensein von Curli-Fasern bestimmt wird. Diese klare Unterscheidung der mechanischen Eigenschaften zwischen Biofilmmatrices mit und ohne Curli ist jedoch in den rheologischen Ergebnissen nicht erkennbar, d. h. nach teilweiser Zerstörung der Matrixarchitektur. Darüber hinaus zeigte die Rheologie eine niedrigere Fließspannung für Biofilme, die Curli enthalten. In der Kombination deuten diese Ergebnisse darauf hin, dass Curli-Fasern spröder und daher stärker von der mechanischen Behandlung betroffen sind. Um die molekularen Wechselwirkungen zwischen der Biofilm-Matrix und Metallkationen zu untersuchen, wurden die drei E. coli-Stämme, die eine Matrix aus Curli-Fasern, pEtN-Zellulose oder beidem bilden, mit abgeschwächter Totalreflexions-Fourier-Transformations-Infrarot-Spektroskopie (ATR-FTIR) charakterisiert. Die von diesen Stämmen produzierten Biofilme wurden in Gegenwart jeder der oben genannten Metallsalzlösungen und in Reinstwasser untersucht. Es wurde gezeigt, dass die drei Stämme anhand ihrer FTIR-Spektren nicht unterschieden werden können und dass in Abwesenheit von pEtN-Zellulose eine mögliche unspezifische Wirkung auf bakterielle Membranen besteht. Ähnliche Experimente mit gereinigten Curli-Fasern oder pEtN-Zellulose deuten darauf hin, dass Metallkationen in erster Linie eine nicht-valenzspezifische Wechselwirkung mit der Phosphatgruppe der pEtN-Modifikation eingehen. Insgesamt zeigen diese Ergebnisse, dass die mechanischen Eigenschaften von E. coli-Biofilmen durch Inkubation mit Metallkationen modifiziert werden können. Während die Mechanismen, an denen Curli-Fasern beteiligt sind, noch nicht aufgeklärt sind, scheinen Metallkationen an pEtN-Zellulose zu adsorbieren. Diese Arbeit unterstreicht auch die Bedeutung der Matrixarchitektur für die Mechanik von Biofilmen und verdeutlicht die Wichtigkeit der jeweiligen Matrixzusammensetzung für die Spezifität und das Ausmaß der beobachteten Effekte. KW - E. coli KW - biofilm KW - metal cation KW - matrix KW - viscoelasticity KW - E. coli KW - Biofilm KW - Metallkation KW - Matrix KW - Viskoelastizität Y1 - 2023 ER - TY - JOUR A1 - Kang, Mi-Sun A1 - Lim, Hae-Soon A1 - Oh, Jong-Suk A1 - Lim, You-jin A1 - Wuertz-Kozak, Karin A1 - Harro, Janette M. A1 - Shirtliff, Mark E. A1 - Achermann, Yvonne T1 - Antimicrobial activity of Lactobacillus salivarius and Lactobacillus fermentum against Staphylococcus aureus JF - Pathogens and disease / Federation of European Microbiology Societies N2 - The increasing prevalence of methicillin-resistant Staphylococcus aureus has become a major public health threat. While lactobacilli were recently found useful in combating various pathogens, limited data exist on their therapeutic potential for S. aureus infections. The aim of this study was to determine whether Lactobacillus salivarius was able to produce bactericidal activities against S. aureus and to determine whether the inhibition was due to a generalized reduction in pH or due to secreted Lactobacillus product(s). We found an 8.6-log10 reduction of planktonic and a 6.3-log10 reduction of biofilm S. aureus. In contrast, the previously described anti-staphylococcal effects of L. fermentum only caused a 4.0-log10 reduction in planktonic S. aureus cells, with no effect on biofilm S. aureus cells. Killing of S. aureus was partially pH dependent, but independent of nutrient depletion. Cell-free supernatant that was pH neutralized and heat inactivated or proteinase K treated had significantly reduced killing of L. salivarius than with pH-neutralized supernatant alone. Proteomic analysis of the L. salivarius secretome identified a total of five secreted proteins including a LysM-containing peptidoglycan binding protein and a protein peptidase M23B. These proteins may represent potential novel anti-staphylococcal agents that could be effective against S. aureus biofilms. KW - antibacterial activity KW - biofilm KW - Lactobacillus fermentum KW - Lactobacillus salivarius KW - LysM KW - Staphylococcus aureus Y1 - 2017 U6 - https://doi.org/10.1093/femspd/ftx009 SN - 2049-632X VL - 75 IS - 2 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Awan, Asad Bashir A1 - Schiebel, Juliane A1 - Boehm, Alexander A1 - Nitschke, Joerg A1 - Sarwar, Yasra A1 - Schierack, Peter A1 - Ali, Aamir T1 - Association of biofilm formation and cytotoxic potential with multidrug resistance in clinical isolates of pseudomonas aeruginosa JF - EXCLI Journal N2 - Multidrug resistant (MDR) Pseudomonas aeruginosa having strong biofilm potential and virulence factors are a serious threat for hospitalized patients having compromised immunity In this study, 34 P. aeruginosa isolates of human origin (17 MDR and 17 non-MDR clinical isolates) were checked for biofilm formation potential in enriched and minimal media. The biofilms were detected using crystal violet method and a modified software package of the automated VideoScan screening method. Cytotoxic potential of the isolates was also investigated on HepG2, LoVo and T24 cell lines using automated VideoScan technology. Pulse field gel electrophoresis revealed 10 PFGE types in MDR and 8 in non-MDR isolates. Although all isolates showed biofilm formation potential, strong biofilm formation was found more in enriched media than in minimal media. Eight MDR isolates showed strong biofilm potential in both enriched and minimal media by both detection methods. Strong direct correlation between crystal violet and VideoScan methods was observed in identifying strong biofilm forming isolates. High cytotoxic effect was observed by 4 isolates in all cell lines used while 6 other isolates showed high cytotoxic effect on T24 cell line only. Strong association of multidrug resistance was found with biofilm formation as strong biofilms were observed significantly higher in MDR isolates (p-value < 0.05) than non-MDR isolates. No significant association of cytotoxic potential with multidrug resistance or biofilm formation was found (p-value > 0.05). The MDR isolates showing significant cytotoxic effects and strong biofilm formation impose a serious threat for hospitalized patients with weak immune system. KW - Pseudomonas aeruginosa KW - multidrug resistance KW - biofilm KW - cytotoxicity KW - VideoScan technology Y1 - 2019 U6 - https://doi.org/10.17179/excli2018-1948 SN - 1611-2156 VL - 18 SP - 79 EP - 90 PB - Leibniz Research Centre for Working Environment and Human Factors CY - Dortmund ER - TY - JOUR A1 - Seiler, Claudia A1 - van Velzen, Ellen A1 - Neu, Thomas R. A1 - Gaedke, Ursula A1 - Berendonk, Thomas U. A1 - Weitere, Markus T1 - Grazing resistance of bacterial biofilms: a matter of predators’ feeding trait JF - FEMS microbiology ecology N2 - Biofilm formation in bacteria is considered to be one strategy to avoid protozoan grazing. However, this assumption is largely based on experiments with suspension-feeding protozoans. Here we test the hypothesis that grazing resistance depends on both the grazers’ feeding trait and the bacterial phenotype, rather than being a general characteristic of bacterial biofilms. We combined batch experiments with mathematical modelling, considering the bacterium Pseudomonas putida and either a suspension-feeding (i.e. the ciliate Paramecium tetraurelia) or a surface-feeding grazer (i.e. the amoeba Acanthamoeba castellanii). We find that both plankton and biofilm phenotypes were consumed, when exposed to their specialised grazer, whereas the other phenotype remained grazing-resistant. This was consistently shown in two experiments (starting with either only planktonic bacteria or with additional pre-grown biofilms) and matches model predictions. In the experiments, the plankton feeder strongly stimulated the biofilm biomass. This stimulation of the resistant prey phenotype was not predicted by the model and it was not observed for the biofilm feeders, suggesting the existence of additional mechanisms that stimulate biofilm formation besides selective feeding. Overall, our results confirm our hypothesis that grazing resistance is a matter of the grazers’ trait (i.e. feeding type) rather than a biofilm-specific property. KW - protozoa KW - biofilm KW - plankton KW - predator-prey model KW - grazing defence KW - feeding trait Y1 - 2017 U6 - https://doi.org/10.1093/femsec/fix112 SN - 0168-6496 SN - 1574-6941 VL - 93 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Wurzbacher, Christian A1 - Warthmann, Norman A1 - Bourne, Elizabeth Charlotte A1 - Attermeyer, Katrin A1 - Allgaier, Martin A1 - Powell, Jeff R. A1 - Detering, Harald A1 - Mbedi, Susan A1 - Großart, Hans-Peter A1 - Monaghan, Michael T. T1 - High habitat-specificity in fungal communities in oligo-mesotrophic, temperate Lake Stechlin (North-East Germany) JF - MycoKeys N2 - Freshwater fungi are a poorly studied ecological group that includes a high taxonomic diversity. Most studies on aquatic fungal diversity have focused on single habitats, thus the linkage between habitat heterogeneity and fungal diversity remains largely unexplored. We took 216 samples from 54 locations representing eight different habitats in the meso-oligotrophic, temperate Lake Stechlin in North-East Germany. These included the pelagic and littoral water column, sediments, and biotic substrates. We performed high throughput sequencing using the Roche 454 platform, employing a universal eukaryotic marker region within the large ribosomal subunit (LSU) to compare fungal diversity, community structure, and species turnover among habitats. Our analysis recovered 1027 fungal OTUs (97% sequence similarity). Richness estimates were highest in the sediment, biofilms, and benthic samples (189-231 OTUs), intermediate in water samples (42-85 OTUs), and lowest in plankton samples (8 OTUs). NMDS grouped the eight studied habitats into six clusters, indicating that community composition was strongly influenced by turnover among habitats. Fungal communities exhibited changes at the phylum and order levels along three different substrate categories from littoral to pelagic habitats. The large majority of OTUs (> 75%) could not be classified below the order level due to the lack of aquatic fungal entries in public sequence databases. Our study provides a first estimate of lake-wide fungal diversity and highlights the important contribution of habitat heterogeneity to overall diversity and community composition. Habitat diversity should be considered in any sampling strategy aiming to assess the fungal diversity of a water body. KW - Freshwater fungi KW - aquatic fungi KW - metabarcoding KW - LSU KW - GMYC KW - habitat specificity KW - Chytridiomycota KW - Cryptomycota KW - Rozellomycota KW - community ecology KW - lake ecosystem KW - biofilm KW - sediment KW - plankton KW - water sample KW - benthos KW - reed KW - fungal diversity Y1 - 2016 U6 - https://doi.org/10.3897/mycokeys.16.9646 SN - 1314-4057 SN - 1314-4049 VL - 41 SP - 17 EP - 44 PB - Pensoft Publ. CY - Sofia ER -