Shedding light on vermiculations: a key step towards their conservation

Caves are hostile environments for life development, due to the prohibitive abiotic factors. However, they host interesting ecological niches for extremophiles, perfectly adapted and specialized. They, in turn, might contribute to the formation processes of the cave and other structures, like vermiculations, enigmatic and still little known deposits, found worldwide on rock surfaces of underground environments. This study, through an interdisciplinary approach, aimed to characterize vermiculations from Pertosa-Auletta Cave (southern Italy), understanding their genesis and nature, indispensable to actuate a protection plan of these singular biosignature. XRD pointed out that they, apart from their colors and morphologies, are mainly composed of calcite, with a lower content of quarts and traces of clay minerals. Elemental analysis showed wide variations in Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, S, Si, Sr, Ti, V and Zn concentrations. NGS analysis highlighted that they swarm of microbial life (Proteobacteria, 48.0%; Acidobacteria, 11.6%; Actinobacteria, 7.1%; Nitrospirae, 5.8%; Firmicutes, 4.3%; Planctomycetes, 3.2%; Chloroflexi, 1.9%; Gemmatimonadetes, 1.1%; Archaea, 0.1%) and a significant percentage of it (13.1%) is likely not yet classified. Also microscopic surveys (CLSM and FE-SEM) revealed the presence of biological evidences, strengthening the hypothesis of a key role of microorganisms in their genesis and development.