Abstract
The microbiota associated with vermiculations from karst caves is largely unknown. Vermiculations are enigmatic deposits forming worm-like patterns on cave walls all over the world. They represent a precious focus for geomicrobiological studies aimed at exploring both the microbial life of these ecosystems and the vermiculation genesis. This study comprises the first approach on the microbial communities thriving in Pertosa-Auletta Cave (southern Italy) vermiculations by next-generation sequencing. The most abundant phylum in vermiculations was Proteobacteria, followed by Acidobacteria > Actinobacteria > Nitrospirae > Firmicutes > Planctomycetes > Chloroflexi > Gemmatimonadetes > Bacteroidetes > Latescibacteria. Numerous less-represented taxonomic groups (< 1%), as well as unclassified ones, were also detected. From an ecological point of view, all the groups co-participate in the biogeochemical cycles in these underground environments, mediating oxidation-reduction reactions, promoting host rock dissolution and secondary mineral precipitation, and enriching the matrix in organic matter. Confocal laser scanning microscopy and field emission scanning electron microscopy brought evidence of a strong interaction between the biotic community and the abiotic matrix, supporting the role of microbial communities in the formation process of vermiculations.
Highlights
The hypogean environments are the least known and studied on Earth [1]
All the 11 studied vermiculations, developing on limestone substratum, showed a considerable biological diversity
The nucleic acids of the whole cells were visualized using the specific SYBR Green fluorescent dye (1:100 dilution), on samples not handled further, under an Olympus FluoView FV1000 confocal laser scanning microscope, and the 488nm excitation laser line with emission signal being collected at 510–530 nm
Summary
The hypogean environments are the least known and studied on Earth [1]. Despite the prohibitive abiotic factors The hypogean environments are the least known and studied on Earth [1]. Difficult to be explained only by pure abiotic physicochemical processes [2]. Recent studies highlighted microbial evidences supporting their biological origin [10, 17,18,19]. Vermiculations can be considered “life hotspots” and a precious support for the studies on cave geomicrobiology. There are still few studies on their microbial characterization and most of these concern vermiculations from sulfuric acid speleogenetic systems [10, 20, 21]
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