Dataset Information

Structure of melanins from the fungi Ochroconis lascauxensis and Ochroconis anomala contaminating rock art in the Lascaux Cave.

ABSTRACT: Two novel species of the fungal genus Ochroconis, O. lascauxensis and O. anomala have been isolated from the walls of the Lascaux Cave, France. The interest in these fungi and their melanins lies in the formation of black stains on the walls and rock art which threatens the integrity of the paintings. Here we report solid-state cross polarization magic-angle spinning ¹³C and ¹⁵N nuclear magnetic resonance (NMR) spectroscopy and surface-enhanced Raman spectroscopy (SERS) of the melanins extracted from the mycelia of O. lascauxensis and O. anomala in order to known their chemical structure. The melanins from these two species were compared with those from other fungi. The melanins from the Ochroconis species have similar SERS and ¹³C and ¹⁵N NMR spectra. Their chemical structures as suggested by the data are not related to 3,4-dihydroxyphenylalanine, 5,6-dihydroxyindole or 1,8-dihydroxynaphthalene precursors and likely the building blocks from the melanins have to be based on other phenols that react with the N-terminal amino acid of proteins. The analytical pyrolysis of the acid hydrolysed melanin from O. lascauxensis supports this assumption.

SUBMITTER: De la Rosa JM

PROVIDER: S-EPMC5647350 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Structure of melanins from the fungi Ochroconis lascauxensis and Ochroconis anomala contaminating rock art in the Lascaux Cave.

De la Rosa José Maria JM Martin-Sanchez Pedro M PM Sanchez-Cortes Santiago S Hermosin Bernardo B Knicker Heike H Saiz-Jimenez Cesareo C

Scientific reports 20171018 1

Two novel species of the fungal genus Ochroconis, O. lascauxensis and O. anomala have been isolated from the walls of the Lascaux Cave, France. The interest in these fungi and their melanins lies in the formation of black stains on the walls and rock art which threatens the integrity of the paintings. Here we report solid-state cross polarization magic-angle spinning <sup>13</sup>C and <sup>15</sup>N nuclear magnetic resonance (NMR) spectroscopy and surface-enhanced Raman spectroscopy (SERS) of ...[more]

PMID: 29044220

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Project description:BACKGROUND:The World-famous UNESCO heritage from the Paleolithic human society, Lascaux Cave (France), has endeavored intense microclimatic perturbations, in part due to high touristic pressure. These perturbations have resulted in numerous disturbances of the cave ecosystem, including on its microbial compartment, which resulted in the formation of black stains especially on the rock faces of the passage. We investigated the cave microbiome in this part of Lascaux by sampling three mineral substrates (soil, banks, and inclined planes) on and outside stains to assess current cave microbial assemblage and explore the possibility that pigmented microorganisms involved in stain development occur as microbial consortia. METHODS:Microbial abundance and diversity were assessed by means of quantitative PCR and high-throughput sequencing (Illumina MiSeq) of several DNA and cDNA taxonomic markers. Five sampling campaigns were carried out during winter and summer to embrace potential seasonal effect in this somewhat stable environment (based on measurements of temperature and CO2 concentration). RESULTS:While the season or type of mineral substrate did not affect the abundances of bacteria and micro-eukaryotes on or outside stains, mineral substrate rather than stain presence appears to be the most significant factor determining microbial diversity and structuring microbial community, regardless of whether DNA or cDNA markers were considered. A phylogenetic signal was also detected in relation to substrate types, presence of stains but not with season among the OTUs common to the three substrates. Co-occurrence network analyses showed that most bacterial and fungal interactions were positive regardless of the factor tested (season, substrate, or stain), but these networks varied according to ecological conditions and time. Microorganisms known to harbor pigmentation ability were well established inside but also outside black stains, which may be prerequisite for subsequent stain formation. CONCLUSIONS:This first high throughput sequencing performed in Lascaux Cave showed that black stains were secondary to mineral substrate in determining microbiome community structure, regardless of whether total or transcriptionally active bacterial and micro-eukaryotic communities were considered. These results revealed the potential for new stain formation and highlight the need for careful microbiome management to avoid further cave wall degradation.

Project description:BackgroundCave anthropization related to rock art tourism can lead to cave microbiota imbalance and microbial alterations threatening Paleolithic artwork, but the underpinning microbial changes are poorly understood. Caves can be microbiologically heterogeneous and certain rock wall alterations may develop in different rooms despite probable spatial heterogeneity of the cave microbiome, suggesting that a same surface alteration might involve a subset of cosmopolitan taxa widespread in each cave room. We tested this hypothesis in Lascaux, by comparing recent alterations (dark zones) and nearby unmarked surfaces in nine locations within the cave.ResultsIllumina MiSeq metabarcoding of unmarked surfaces confirmed microbiome heterogeneity of the cave. Against this background, the microbial communities of unmarked and altered surfaces differed at each location. The use of a decision matrix showed that microbiota changes in relation to dark zone formation could differ according to location, but dark zones from different locations displayed microbial similarities. Thus, dark zones harbor bacterial and fungal taxa that are cosmopolitan at the scale of Lascaux, as well as dark zone-specific taxa present (i) at all locations in the cave (i.e. the six bacterial genera Microbacterium, Actinophytocola, Lactobacillus, Bosea, Neochlamydia and Tsukamurella) or (ii) only at particular locations within Lascaux. Scanning electron microscopy observations and most qPCR data evidenced microbial proliferation in dark zones.ConclusionFindings point to the proliferation of different types of taxa in dark zones, i.e. Lascaux-cosmopolitan bacteria and fungi, dark zone-specific bacteria present at all locations, and dark zone-specific bacteria and fungi present at certain locations only. This probably explains why dark zones could form in various areas of the cave and suggests that the spread of these alterations might continue according to the area of distribution of key widespread taxa.

Project description:Fungi are important contaminants of historic canvas paintings worldwide. They can grow on both sides of the canvas and decompose various components of the paintings. They excrete pigments and acids that change the visual appearance of the paintings and weaken their structure, leading to flaking and cracking. With the aim of recognizing the most dangerous fungal species to the integrity and stability of paintings, we studied 55 recently isolated and identified strains from historic paintings or depositories, including 46 species from 16 genera. The fungi were categorized as xero/halotolerant or xero/halophilic based on their preference for solutes (glycerol or NaCl) that lower the water activity (aw) of the medium. Accordingly, the aw value of all further test media had to be adjusted to allow the growth of xero/halophilic species. The isolates were tested for growth at 15, 24 °C and 37 °C. The biodeterioration potential of the fungi was evaluated by screening their acidification properties, their ability to excrete pigments and their enzymatic activities, which were selected based on the available nutrients in paintings on canvas. A DNase test was performed to determine whether the selected fungi could utilize DNA of dead microbial cells that may be covering surfaces of the painting. The sequestration of Fe, which is made available through the production of siderophores, was also tested. The ability to degrade aromatic and aliphatic substrates was investigated to consider the potential degradation of synthetic restoration materials. Xerotolerant and moderately xerophilic species showed a broader spectrum of enzymatic activities than obligate xerophilic species: urease, β-glucosidase, and esterase predominated, while obligate xerophiles mostly exhibited β-glucosidase, DNase, and urease activity. Xerotolerant and moderately xerophilic species with the highest degradation potential belong to the genus Penicillium, while Aspergillus penicillioides and A. salinicola represent obligately xerophilic species with the most diverse degradation potential in low aw environments.

Dataset Information

Structure of melanins from the fungi Ochroconis lascauxensis and Ochroconis anomala contaminating rock art in the Lascaux Cave.

Publications

Structure of melanins from the fungi Ochroconis lascauxensis and Ochroconis anomala contaminating rock art in the Lascaux Cave.

Similar Datasets

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