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The Great Pacific Garbage Patch, a significant collection of plastic introduced by human activities, provides an ideal environment to study bacterial lifestyles on plastic substrates. We proposed that bacteria colonizing the floating plastic debris would develop strategies to deal with the ultravioletexposed substrate, such as the production of antioxidant pigments. We observed a variety of pigmentation in 67 strains that were directly cultivated from plastic pieces sampled from the Garbage Patch. The genomic analysis of four representative strains, each distinct in taxonomy, revealed multiple pathways for carotenoid production. These pathways include those that produce
less common carotenoids and a cluster of photosynthetic genes. This
cluster appears to originate from a potentially new species of the Rhodobacteraceae family. This represents the first report of an aerobic anoxygenic photoheterotrophic bacterium from plastic biofilms. Spectral analysis showed that the bacteria actively produce carotenoids, such as betacarotene and beta-cryptoxanthin, and bacteriochlorophyll a. Furthermore, we discovered that the genetic ability to synthesize carotenoids is more common in plastic biofilms than in the surrounding water communities. Our findings suggest that plastic biofilms could be an overlooked source of bacteria-produced carotenoids, including rare forms. It also suggests that photoreactive molecules might play a crucial role in bacterial biofilm communities in surface water.
Dihydroxynaphthalene (DHN) melanin is produced by diverse Ascomycetes via slightly differing biosynthetic routes. The polyketide synthases (PKS) release the heptaketide YWA1, the hexaketide AT4HN or the pentaketide T4HN. The first two products are deacetylated by ‘yellowish-green’ hydrolases to T4HN, and T4HN is further converted by a core set of enzymes to DHN. Final polymerization steps are accomplished by multicopper oxidases. DHN melanogenesis is often regulated in a spatial and temporal fashion resulting e.g., in melanized reproduction and survival structures of the foliar plant pathogen Botrytis cinerea (Schumacher 2016, Mol Microbiol). In contrast, a polyphyletic group of Ascomycetes (microcolonial fungi/ black yeasts) dwelling in hostile habitats such as bare rock surfaces in hot and cold deserts, exhibits constitutive melanogenesis. Here, DHN melanin builds a protective layer around all vegetative cells thus contributing to the survival of diverse environmental stresses even without specialized reproduction structures. For studying the relevance of constitutive DHN melanogenesis for tolerance of abiotic and biotic stresses, adhesion to substrates and subsequent damage of colonized surfaces, the rock-inhabiting fungus Knufia petricola was chosen as gene functions in this fungus can be studied by CRISPR/Cas9-based genome editing. The putative melanogenic genes were identified in the genome of K. petricola, deleted to confirm their involvement in DHN melanogenesis and co-expressed in Saccharomyces cerevisiae for reconstruction of the synthesis pathway. Phenotypes of DHN-deficient mutants are studied. Here, we will discuss the role of the DHN melanin layer on the outer cell wall in tolerating UV irradiation.
Dihydroxynaphthalene (DHN) melanin is produced by diverse Ascomycetes via slightly differing biosynthetic routes. The polyketide synthases (PKS) release the heptaketide YWA1, the hexaketide AT4HN or the pentaketide T4HN. The first two products are deacetylated by ‘yellowish-green’ hydrolases to T4HN, and T4HN is further converted by a core set of enzymes to DHN. Final polymerization steps are accomplished by multicopper oxidases. DHN melanogenesis is often regulated in a spatial and temporal fashion resulting e.g., in melanized reproduction and survival structures of the foliar plant pathogen Botrytis cinerea (Schumacher 2016, Mol Microbiol). In contrast, microcolonial black fungi exhibit constitutive melanogenesis. Here, DHN melanin builds a protective layer around all vegetative cells thus contributing to the survival of diverse environmental stresses even without specialized reproduction structures. For studying the regulation and relevance of DHN melanogenesis for tolerance of abiotic and biotic stresses, adhesion to substrates and subsequent damage of colonized surfaces, the rock-inhabiting fungus Knufia petricola was chosen as gene functions in this fungus can be studied by CRISPR/Cas9-based genome editing. The putative melanogenic genes were identified in the genome of K. petricola, deleted to confirm their involvement in DHN melanogenesis and co-expressed in Saccharomyces cerevisiae for reconstruction of the synthesis pathway. Phenotypes of deletion mutants are studied for specifying the functions of DHN melanin in K. petricola.
Z02 is one of the three technically supporting projects at the Centre for the Study of Manuscript Cultures (CSMC). In collaboration with the other two service projects, Z01 and Z03, it aims at bridging the gap between humanities and natural sciences and technology. To that purpose, we set up a laboratory with a range of high-end instruments, most of them mobile, allowing thorough non-destructive analysis of manuscripts. In addition to working on constantly improving the laboratory and the methods of analysis, a substantial part of our activities is dedicated to service, by supporting different research projects conducted at the centre. In this talk, we will present our equipment and the possibilities offered by the different techniques available regarding the different kinds of missions: typology and classification of inks, provenance studies, recovery of faded inscriptions and palimpsests, reconstruction of the history of manuscripts, authentication and dating. We will give a brief overview of our past and ongoing activities in the frame of the second phase of the CSMC. Finally, a selection of three projects will be presented in greater detail to highlight the possibilities of our laboratory and the diversity of missions which can be carried out.
Z02 is one of the three technically supporting projects at the CSMC. In collaboration with Z01 and Z03, it aims at bridging the gap between humanities and natural sciences and technology. To that purpose, we set up a laboratory with a range of high-end instruments, most of them mobile, allowing thorough non-destructive analysis of manuscripts. In addition to working on constantly improving the laboratory and the methods of analysis, a substantial part of our activities is dedicated to service, by supporting different research projects conducted at the center.
In this talk, we will present our equipment and the possibilities offered by the different techniques available regarding the different kinds of missions: typology and classification of inks, provenance studies, recovery of faded inscriptions and palimpsests, reconstruction of the history of manuscripts, authentication and dating. We will give a brief overview of our past and ongoing activities in the frame of the second phase of the CSMC. Finally, a selection of three projects will be presented in greater detail to highlight the possibilities of our laboratory and the diversity of missions which can be carried out:
- Support of project C08 on East Frankish manuscripts containing collections of formulae
- Identifying color materials applied in Muhammad Juki's Shahnamah with non-invasive combined methods
- Checking for the presence of metals in the Herculaneum papyri
A non-invasivemethod has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings “Zwei Frauen am Tisch” (1920–22), “Bäume” (1946) (both by Heinrich Campendonk), “Lofoten” (1933) (Edith Campendonk-van Leckwyck) and “Ohne Titel” (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra fromthe paintingswith spectra frompure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts.We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.
The manuscript of the History of Outremer by William of Tyre stored at the BNF (ms. fr. 9084) is believed to have been illustrated by two different hands. Indeed, the first five miniatures of this manuscript appear to be very different from the last seventeen, which were supposedly painted by an artist known as the "Hospitaller Master". This painter worked on at least two manuscripts in Paris between 1276 and 1280, and eight more in Saint Jean d'Acre before 1291. During his stay in the Latin Kingdom of Jerusalem, his palette changed and reached its most important development in the Manuscript of the History of Outremer, maybe influenced by the colourful crusader style of the first five miniatures. The present work aims at identifying the pigments used on both parts of the manuscripts and see whether they are the same for both artists or not. For that, portable XRF analysis was used directly at the Bibliothèque National de France in Paris, where the manuscript is stored. This allowed a quick, non destructive and non invasive study of the manuscript. Significant differences were observed in the compositions of some pigments indeed, in particular for the red and green, showing the use of different palettes. This could indicate that the Hospitaller Master not only brought his knowledge and style, but also probably part of his palette of pigments with him when moving to Saint Jean d'Acre.
Biocides are commonly applied to building materials such as renders and paints in order to protect them from microbial spoilage. Since the building materials are commonly exposed to weathering conditions, biocides incorporated within the material matrices tend to leach out during the rain events. Moreover, photodegradation processes play an important role in the fate of biocides, due to the exposure to natural sunlight. Leaching of biocides and their moderate persistence, indicate that photodegradation products of biocides can also be found as environmental contaminants in runoff waters. In this study we investigated the photodegradation of four commonly used biocides (carbendazim, diuron, octylisothiazolinone and terbutryn) in four different paint formulations with selected pigments (red, white, black and one artificial, not commercial pigment-free formulation for comparison). As pigments interact with the spectrum of the incoming light, the effect of pigments on photodegradation rates was assumed to be relevant.
Samples were prepared by painting 2 layers of selected paints on glass plates. The dry paint samples were exposed to UV light for designated time periods ranging from 0 h to 1056 h of total exposure time in a commercial UV-Test® Fluorescent / UV Instrument (Atlas Material Testing Technology, Illinois, USA). The applied energy was 1.2 W/m2. The black panel temperature was established at 40 ºC. The radiant energy from the UV fluorescent lamps was concentrated in the wavelength region at 351 nm and below. All samples were prepared in triplicates. After irradiation, paint samples were removed from glass carriers and extracted with methanol. The remaining biocide concentrations as well as the amounts of photodegradation products were analysed with the use of liquid chromatography coupled to mass spectrometry.
The transparent, pigment-free formulation was the most vulnerable to light exposure, a visible colour change from white to yellow was observed after 1056 h of irradiation. Diuron, octylisothiazolinone and terbutryn degraded from pigment-free formulation following first-order degradation kinetics. A decrease of carbendazim was also observed. The remaining formulations showed similar degradation patterns for all analysed biocides. All paints showed degradation for octylisothiazolinone with 3-octyl-2(3H)-thiazolone being the main product for red, white and black pigment paint. N-octylacetamide and N-octyloxamic acid were dominant in the pigment-free formulation. Terbutryn sulfoxide was the main degradation product of terbutryn in case of the white paint, while other pigments showed higher concentrations of desbuthyl-2-hydroxy-terbutryn and desethyl-2-hydroxy-terbutryn.
A determination of photodegradation in terms of pigment type, measured light spectra and intensity as outlined in this study, could provide a basis for establishing a quantitative description of the fate of biocides in paints, which has significance not only in terms of environmental science, but also could provide a guideline for developing new and effective products.
Black ascomycetous microcolonial fungi (MCF) are persistent inhabitants of rock surfaces in deserts as well as ubiquitous in other wide-spread terrestrial ecosystems including man-made materials such as solar panels. The ability of MCF to cope with multiple, rapidly fluctuating stresses makes the group an interesting subject in the study of stress resistance. Carotenoids and melanin are amongst the protective pigments that contribute to the robustness of MCF. We studied their role in stress resistance of the non-pathogenic rock-inhabiting fungus Knufia petricola (Chaetothyriales) strain A95. Disruption of melanin synthesis affects not only oxidative-stress resistance but also the extracellular polysaccharide (EPS) matrix and lipid composition of the cell membrane.
Microcolonial fungi (MCF) are the most stress-resistant eukaryotes known to date. Black fungi are an interesting object to study mechanisms of stress resistance and to perform applied research to prevent material colonization and biodeterioration. Pigments, like melanin and carotenoids, have been proven to contribute to the unique robustness of MFCs. We study how these pigments ameliorate oxidative stress responses - one of the most significant environmental challenges encountered by MCF - using the model rock fungus Knufia petricola (Chaetothyriales) strain A95.