Characterization of the microbial community in the Cova des Pas de Vallgornera

Abstract

[eng] In the current study the microbial diversity from the Cova des Pas de Vallgornera located in the southeast coast of Mallorca was analyzed. The samples were taken in “Galeria d’en Pau” situated in the center of the endokarstic system and about 2 km from the entrance. Samples were taken from drip-water falling from speleothems, water from gours and phreatic lakes in semi-submerged galleries. Microbial diversity was evaluated by a metagenomic approach. Drip-water and gours showed lower diversity and shared a major number of taxonomic units than the brackish waters. Moreover, the binned Metagenome Assembled Genomes (MAGs) from the most abundant populations allowed performing phylogenetic studies. From a total of 14 MAGs recovered from drip-water and gours, the most abundant were associated to the Acinetobacter genus, Sphingomonadaceae family and the class Gammaproteobacteria. Members of the genus Acinetobacter represented 2 different species, associated to bio-mineralization processes contributing to calcareous structures formation. Additionally, related to Archaea domain, 5 MAGs recovered were associated to the family Nitrososphaeraceae and Nitrosopumilaceae, whose chemolithoauthotroph and ammonia-oxidizing metabolism could be linked to part of the primary production in the cave. On the other hand, samples from phreatic lakes showed higher diversity and it was possible to recover 27 MAGs. The most abundant MAGs affiliated with the family Comamonadaceae and Nitrospiraceae. Additionally, 3 MAGs affiliated with the archaeal domain: i.e. Candidatus Nitrosoarchaeum, Nitrososphaera and Thaumarchaeota archeon of the phylum Thaumarchaeota, also indicating that in these systems the primary production can be associated by ammoniaoxidizing microorganisms as in the other samples.