Dark-zone alterations expand throughout Paleolithic Lascaux Cave despite spatial heterogeneity of the cave microbiome

Abstract

Background Cave 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. Results Illumina 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. Conclusion Findings 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.

Deconstructing the Dimensions of Mycobiome Fingerprints in Luohandu Cave, Guilin, Southern China

“…With breakthroughs in the bottleneck of DNA extraction from cave rock samples and high-throughput meta-barcoding revolutionizing our understanding of global fungal diversity and function, much of the previously “hidden diversity”, new taxa and previously unknown fungal lineages are continuously revealed in subterranean karst caves [ 7 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Although the results of these studies constantly increase our understanding of the genetic diversity, ecology and evolution of fungi, improving mural preservation and drug discovery, cave-dwelling fungi still have received far less attention than prokaryotes [ 4 , 5 , 17 ]. Previous studies showed that karst caves are populated predominantly by rock-inhabiting fungi of two classes of Ascomycota: Dothideomycetes and Eurotiomycetes [ 18 , 19 ].…”

“…This is particularly true for subterranean environments such as Microorganisms 2024, 12, 211 2 of 18 karst caves, which serve as reservoirs for specialized fungi, despite the hostile environment that prevails in the absence of light and in the presence of high mineral concentrations, high humidity and a low organic carbon input [4]. As typical extreme subterranean environments with spatial heterogeneity of the cave microbiome [5], such sites may hold an incredible "dark fungal diversity", which is still underestimated.…”