Functional Characterisation of Microbial Communities Related to Black Stain Formation in Lascaux Cave.

Anthropization of Palaeolithic caves may cause cave microbiota dysbiosis and promote the development of microbial stains on cave walls. In certain cases, chemical biocides have been used to mitigate rock alterations, but this may exacerbate microbiota unbalance. Here, we tested this model by metagenomics, using black stains that threaten art conservation in Lascaux Cave. Thus, we evidenced a wide range of microbial taxa differing between black stains and neighbouring unmarked surfaces. Genes for synthesis of melanin and carotenoid pigments were more prevalent in black stains and were identified in reconstructed genomes for fungi (as expected) and bacteria. The presence of genes for degradation of aromatic compounds supports the hypothesis that recycling of chemical biocides favoured melanin-producing microorganisms. These findings extend previous predictions by revealing a wider range of microorganisms, potential biotransformations favouring pigment synthesis, as well as microbial interactions influencing microbial dynamics during cave wall alterations.