Cave microbiota plays a key role in the genesis processes of underground environments. In fact, they are involved in the biogeochemical cycles, interacting with the rock substrates through both constructive and destructive pathways and contributing to the formation of speleothemes (1), such as vermiculations, still unexplored peculiar sedimentary structures, occurring on the walls of natural or artificial caves (2). Latest researches pointed out microbial evidences supporting their biological origin (3). The goal of the work was to shed light on the geochemical and microbiological characteristics of vermiculations from Pertosa-Auletta Cave (Campania, southern Italy), contributing also to the knowledge of microbial biodiversity of such karst system. Next-generation sequencing surveys showed the occurrence of Proteobacteria (48.0%), Acidobacteria (11.6%), Actinobacteria (7.1%), Nitrospirae (5.8%), Firmicutes (4.3%), Planctomycetes (3.2%), Chloroflexi (1.9%), Gemmatimonadetes (1.1%). Numerous less-represented bacterial groups (< 1%), Archaea (0.1%), as well as a significant percentage of unclassified microorganisms (13.1%), were also detected. X-ray diffraction revealed the mainly calcitic composition of the deposits, with a low amount of quarts and clay minerals. Moreover, they exhibited a 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 among the analyzed samples. Field emission scanning electron and confocal laser scanning microscopy supported the hypothesis of the functional microbial activity in the development of vermiculations, highlighting several dissolution shapes, but also the presence of biogenic secondary minerals and organic matter. 1. Tomczyk-Żak, K. and Zielenkiewicz, U. (2016) Geomicrobiology Journal 33:20–38. 2. Hill, C.A. and Forti, P. (1997). Cave minerals of the world. National Speleological Society II Edition 463. 3. Jones, D.S. et al. (2008) Journal of Cave and Karst Studies 70(2): 78-93.
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