4 Material und Umwelt
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Eingeladener Vortrag
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Microbiologically induced corrosion due to bacterial biofilms causes several problems in industrial systems, technical applications and in medicine. Prior to the formation of a biofilm on a substrate, planktonic cells attach on the surface. Hence, the properties of the surface play a key role in biofilm formation and are of great importance for the development of strategies to prevent bacterial attachment and biofilm formation.
This project aims at clarifying to which extent surface micro-/nanostructuring and chemical functionalization affects bacterial attachment and whether a synergistic combination of the two can be used to control bacterial adhesion. To answer these questions, model surfaces with regular patterns of 5-10 micrometers in size have been prepared, which provide distinct zones differing in terms of their chemistry or nano-roughness. This was achieved by micro contact printing of self-assembled monolayers with different functional groups and deposition of patterned ZnO nanorod arrays for studying the effect of surface chemistry and morphology, respectively. Typical contrasts studied were combinations of positively/negatively charged, hydrophobic/hydrophilic or flat/rough.
The attachment behavior of bacteria on tailored surfaces were studied in a flow chamber as a function of time. The strain Pseudomonas fluorescens SBW25 was chosen as a model organism. DNA-intercalating dyes such as Syto9 have a high affinity to adsorb on ZnO nanorods. To overcome this limitation a genetic modification was performed by introducing a gene which expresses a green fluorescent protein in P. fluorescens SBW25 enabling the quantitative evaluation of the flow chamber studies by means of fluorescence microscopy. Further analysis of the attachment behavior was performed by means of scanning electron microscopy.
The presentation will summarize the results of our systematic study on the role of individual parameters on bacterial attachment and highlight synergistic combinations, showing an inhibition or enhancing effect. As the investigations with model substrates enable a precise control of the surface parameters, this approach can be applied to different microorganisms and material systems to achieve a correlative description of bacterial adhesion on solid surfaces.
The rotation of the Earth causes a day/night cycle that is characterized by changing light and temperature conditions. Fungi actively sense the environmental light conditions to induce protective mechanisms against the light-associated stresses and to regulate development. Since fungi adapted to habitats with different light regimes, the complexities of their ‘visual’ systems and photoresponses may vary significantly. Fungi that are associated with plants experience a special light regime because the host seeks optimum light conditions for photosynthesis – and the fungus must cope with them. Moreover, fungi living under the canopy are confronted with an altered spectrum enriched for green and far-red light. Plants sense light to coordinate growth and morphogenesis: a low red:far-red ratio indicates the presence of competitors (shading by other plants) and triggers the shade avoidance response which is accompanied by increased susceptibility to nectrophic pathogens.
Botrytis cinerea, the causal agent of gray mold diseases on many plant species in moderate climate zones (high humidity, temperatures around 20°C, seasons), exhibits striking photoresponses accompanied by a broad action spectrum and a high number of photoreceptors. Light is the most important factor controlling morphogenesis: it induces conidiation for disease spreading (summer cycle) and represses sclerotial development for survival and/or sexual recombination (winter cycle). In the past years, we identified several cellular components involved in photoperception and regulation of photomorphogenesis and virulence indicating that the same signaling pathways are of relevance for both processes, propagation and infection. Notably, we recognized the role of the phytochromes (red/far-red light sensors) for coordinated responses to light and elevated temperatures (photo-/thermomorphogenesis) – similar to the function of Arabidopsis PhyB. BcPHY2-like thermosensors are likely restricted to the Leotiomycetes, which include several plant pathogens of the moderate climate zones.
Sunlight, the major source of energy, drives life but in excess it provokes UV-induced DNA damage, accumulation of reactive oxygen species, desiccation, osmotic stresses and so on. Biological strategies to survive excess light include protection, avoidance and active utilisation. Phototrophic organisms including cyanobacteria, green algae and plants use all three strategies. Fungi occupying phototrophic niches may profit from the surplus photosynthetic products which also obliges them to cope with the same light-induced stresses. One way of handling these stresses would be to use similar signalling pathways to sense the presence and to interact with their phototrophic partners. Obviously, the levels of adaptation and responses to light will depend on the environment as well as fungal genotype and phylogenetic position. Black fungi – a polyphyletic group – accumulate the dark pigment DHN melanin in their cell walls and often occupy light-flooded habitats from phyllosphere to rock surfaces. Here we compare two sequenced melanised fungi of different lifestyles in their response to light.
The Leotiomycete Botrytis cinerea is an aggressive pathogen that primarily infects the above-ground parts of plants. It possesses large numbers of photoreceptors that respond to a broad spectrum of light. As a consequence, light controls morphogenesis in which it induces conidiation for disease spreading and represses sclerotial development for survival and/or sexual recombination. Cellular components involved in photo-perception and regulation of morphogenesis, stress responses and virulence have been identified and appear to regulate propagation, survival and infection. These include phytochromes, a group of photoreceptors which are particularly enriched in the Leotiomycetes and that mediate coordinated responses to light and elevated temperatures. Assuming that photo-regulation may be equally important for fungi that live in mutualistic relationships with phototrophs either by forming composite organisms or biofilms, we investigate the role of light in the rock-inhabiting Eurotiomycete Knufia petricola. Like other black yeasts, K. petricola grows slowly, does not form specialised reproductive structures and constitutively produces DHN melanin as well as carotenoids. Combining K. petricola with the cyanobacterium Nostoc punctiforme, we developed a model system for studying biofilm formation and bio-weathering. A genetic toolbox to manipulate this model system is being developed. K. petricola strain A95 possesses ten putative photoreceptors, more than found in filamentous Eurotiomycetes suggesting that light plays an important role for abiotic and biotic interactions in extremo-tolerant and symbiosis-capable fungi.
Fungi that share light-flooded habitats with phototrophs may profit from excess photosynthetic products. But to cope with sunlight-associated stresses it is important for fungi to accurately sense and respond to changes in light. To test the hypothesis that light is an environmental cue that Ascomycota use to coordinate growth, stress responses as well as to establish pathogenic or symbiotic relationships, the photoreceptor (PR) distribution in species from different ecological niches was analysed. The genomes of black fungi from phyllosphere and exposed solid surfaces contain multiple photoreceptors (PRs). The filamentous foliar plant pathogen Botrytis cinerea (Leotiomycetes) has a highly sophisticated photosensory and signalling system that helps to avoid light and to locate susceptible hosts. Rock-inhabiting Dothideo- and Eurotiomycetes including Knufia petricola possess equal numbers of PRs along with the same set of protective pigments. This similarity between black fungi from plant and rock surfaces suggests that photoperception and photoregulation are important for fungi that avoid loss of energy and nutrients through cooperation with phototrophs.
Fungi that share light-flooded habitats with phototrophs may profit from excess photosynthetic products. But to cope with sunlight-associated stresses it is important for fungi to accurately sense and respond to changes in light. To test the hypothesis that light is an environmental cue that Ascomycota use to coordinate growth, stress responses as well as to establish pathogenic or symbiotic relationships, the photoreceptor (PR) distribution in species from different ecological niches was analysed. The genomes of black fungi from phyllosphere and exposed solid surfaces contain multiple photoreceptors (PRs). The filamentous foliar plant pathogen Botrytis cinerea (Leotiomycetes) has a highly sophisticated photosensory and signalling system that helps to avoid light and to locate susceptible hosts. Rock-inhabiting Dothideo- and Eurotiomycetes including Knufia petricola possess equal numbers of PRs along with the same set of protective pigments. This similarity between black fungi from plant and rock surfaces suggests that photoperception and photoregulation are important for fungi that avoid loss of energy and nutrients through cooperation with phototrophs.
A fundamental question in ecology is how biodiversity affects ecosystem function. Biodiversity is commonly estimated based on genetic variation. We investigated a new approach that defines and measures biodiversity in complex microbial communities. We used the variation in multiple functionally-relevant, phenotypic traits measured in parallel in single cells as a metric for microbial phenotypic diversity. We studied phenotypic diversity and ecosystem functioning throughout different photosynthetic layers dominated by divergent microbial communities in the gradient of Lago di Cadagno. We determined genetic diversity by 16S and 18S amplicon sequencing and bulk ecosystem functioning (photosynthesis). In addition, we determined phenotypic diversity using single-cell technologies such as nanometer-scale secondary ion mass spectrometry (NanoSIMS) correlated with confocal laser scanning microscopy (CLSM) and scanning flow-cytometry. We measured functional trait variation between individuals in 13CO2 fixation, 15NH4+ uptake, and variation in physio-morphological cell traits, such as cell size, shape, and auto-fluorescence for various pigments related to photosynthesis. We used the distances between individuals in a multidimensional trait space to derive phenotypic trait-based diversity indices, such as trait richness, trait evenness, and trait divergence. We find that phenotypic trait divergence associates with ecosystem functioning, whereas genetic diversity does not. Including activity-based, single-cell phenotypic measurements with NanoSIMS provided an additional accuracy to the trait-based diversity assessment and allowed us to formulate hypotheses on the mechanisms that shape the correlation between phenotypic diversity and eco-system function. Together, our results show that phenotypic diversity is a meaningful concept to measure microbial biodiversity and associate it with ecosystem functioning.
OECD test guideline on particle size and size distribution: Comparability of measurement results
(2019)
OECD-Prüfrichtlinien werden weltweit für regulatorische Zwecke angewandt, da sie eine harmonisierte und über internationale Ringversuche validierte Vorschrift zur Analyse vorgeben. Die bestehende Prüfrichtlinie TG 110 zur Größencharakterisierung von Partikeln und Fasern ist für viele Methoden und Materialklassen nicht geeignet, weswegen es Bedarf an einer Neuentwicklung gibt. Im Fokus der neuen TG steht die reproduzierbare und vergleichbare Anwendung von Methoden zur Bestimmung von Partikelgröße sowie Größenverteilung annährend sphärischer und faserförmiger Nanomaterialien im Bereich 1-1000 nm. Berücksichtigt werden die häufig angewandten Methoden zur Größencharakterisierung mit ihren unterschiedlichen physikalisch-technischen Limitierungen und die Bestimmung unterschiedlicher Durchmesser (hydrodynamischer, Feret…). Weiterhin sind materialspezifische Einflüsse durch die Partikel sowie das Messmedium zu berücksichtigen. Jede der Methoden soll unter Berücksichtigung von ISO-Standards und den materialspezifischen Limitierungen in der neuen Prüfrichtlinie beschrieben und über einen Ringversuch validiert werden.
CFK-Abfälle werden trotz der bestehenden Verfahren zur Rückgewinnung der Carbonfasern zukünftig vermehrt anfallen. Für diese Abfälle wird nach technischen Lösungen der energetischen oder stofflichen Verwertung gesucht. Eine Möglichkeit ist die Nutzung der CFK-Abfälle als Primärkohleersatz im Lichtbogenofen bei der Stahlherstellung.