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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.
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.
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.
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.