Caves constitute fascinating ecological niches for microorganisms, among which the chemolithoautotrophic constitute the main primary producers of these ecosystems. The role of cave microbiota in the formation of speleothems and other structures like vermiculations is still debated. Vermiculations are enigmatic deposits of incoherent particles, observable on walls and ceilings of worldwide natural or artificial caves, varying in morphology, color and size. They teem with life and represent interesting systems to understand the ecological role of biota in the cave ecosystem. The aim of this study was to contribute to the understanding of vermiculation nature and of the ecological interactions involved in their genesis and development. To this end, an integrated approach including geochemical, microbiological and microscopic surveys, was applied on 11 vermiculation types from Pertosa-Auletta Cave (Campania, southern Italy), exhibiting an exceptional diversity and abundance of these structures. XRD analyses revealed that vermiculations are mainly composed of calcite, with variable fractions of minor constituents like quartz, clay minerals, siderite and feldspars. 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 vermiculations were highlighted by elemental analysis, due to substrate characteristics and deposition of exogenous inorganic and organic matter. 16S rRNA NGS survey showed that Proteobacteria (48.0%) was the most abundant phylum in the Bacteria domain, followed by Acidobacteria (11.6%), Actinobacteria (7.1%), Nitrospirae (5.8%), Firmicutes (4.3%), Planctomycetes (3.2%), Chloroflexi (1.9%) and Gemmatimonadetes (1.1%). Archaea (0.1%) and a significant percentage of unclassified microorganisms (13.1%) were also observed. FE-SEM and CLSM confirmed the presence of microorganisms and of their activity, supporting the hypothesis of a direct involvement of microorganisms in the development of vermiculations, through the production of organic matter, precipitation of secondary minerals, sediment trapping and binding, etching or pitting of the host rock.

Cave vermiculations and microbiota, an ecological journey

Addesso R.;Baldantoni D.;Bellino A.
2019

Abstract

Caves constitute fascinating ecological niches for microorganisms, among which the chemolithoautotrophic constitute the main primary producers of these ecosystems. The role of cave microbiota in the formation of speleothems and other structures like vermiculations is still debated. Vermiculations are enigmatic deposits of incoherent particles, observable on walls and ceilings of worldwide natural or artificial caves, varying in morphology, color and size. They teem with life and represent interesting systems to understand the ecological role of biota in the cave ecosystem. The aim of this study was to contribute to the understanding of vermiculation nature and of the ecological interactions involved in their genesis and development. To this end, an integrated approach including geochemical, microbiological and microscopic surveys, was applied on 11 vermiculation types from Pertosa-Auletta Cave (Campania, southern Italy), exhibiting an exceptional diversity and abundance of these structures. XRD analyses revealed that vermiculations are mainly composed of calcite, with variable fractions of minor constituents like quartz, clay minerals, siderite and feldspars. 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 vermiculations were highlighted by elemental analysis, due to substrate characteristics and deposition of exogenous inorganic and organic matter. 16S rRNA NGS survey showed that Proteobacteria (48.0%) was the most abundant phylum in the Bacteria domain, followed by Acidobacteria (11.6%), Actinobacteria (7.1%), Nitrospirae (5.8%), Firmicutes (4.3%), Planctomycetes (3.2%), Chloroflexi (1.9%) and Gemmatimonadetes (1.1%). Archaea (0.1%) and a significant percentage of unclassified microorganisms (13.1%) were also observed. FE-SEM and CLSM confirmed the presence of microorganisms and of their activity, supporting the hypothesis of a direct involvement of microorganisms in the development of vermiculations, through the production of organic matter, precipitation of secondary minerals, sediment trapping and binding, etching or pitting of the host rock.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/4728055
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