Rock substrate rather than black stain alterations drives microbial community structure in the passage of Lascaux Cave

Abstract

BackgroundThe 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.MethodsMicrobial 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).ResultsWhile 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.ConclusionsThis 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.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0599-9) contains supplementary material, which is available to authorized users.

Diversity, Distribution and Co-occurrence Patterns of Bacterial Communities in a Karst Cave System

“…However, we did find significant differences among bacterial communities in terms of their occupied niches (i.e., air, rock, sediment, and water), not unlike Brannen-Donnelly and Engel (2015) who reported that bacterial community composition in cave streams and sediments differed at the class level. More recently, Alonso et al (2018) reported that mineral substrate was the most significant factor determining cave microbial diversity and structure. Other studies also showed that the bacterial communities associated with dripping water in the Heshang Cave in central China were mostly dominated by Proteobacteria , while Actinobacteria was the most dominant phyla in weathered rocks in the same cave (Yun et al, 2016a, b).…”

Anthropization level of Lascaux Cave microbiome shown by regional‐scale comparisons of pristine and anthropized caves

“…Man-made layout Fittings Tourism Microbial outbreaks Chemical treatments Pristine caves: (Alonso et al, 2018), whose walls correspond to the same Cognacien limestone sampled in the other caves. Microbial outbreaks in Lascaux have been described (Bastian, Alabouvette, Jurado, et al, 2009).…”

“… Lascaux samples were taken from the Shaft of the Dead Man (in the Diaclase) and the inclined plane in the Passage (Alonso et al, ), whose walls correspond to the same Cognacien limestone sampled in the other caves. Microbial outbreaks in Lascaux have been described (Bastian, Alabouvette, Jurado, et al, ). …”

The Ecology of Subaerial Biofilms in Dry and Inhospitable Terrestrial Environments

“…A recent study carried out on SABs colonizing the passage of Lascaux Cave revealed that mineral substrates were important drivers structuring both the total (DNA) and the metabolically active (RNA) microbial communities, more so than the presence of black discoloration and the seasonality did [43].…”