Airborne bacteria in show caves from Southern Spain

Abstract

This work presents a study on the airborne bacteria recorded in three Andalusian show caves, subjected to different managements. The main differences within the caves were the absence of lighting and phototrophic biofilms in Cueva de Ardales, the periodic maintenance and low occurrence of phototrophic biofilms in Gruta de las Maravillas, and the abundance of phototrophic biofilms in speleothems and walls in Cueva del Tesoro. These factors conditioned the diversity of bacteria in the caves and therefore there are large differences among the CFU m-3, determined using a suction impact collector, equipment widely used in aerobiological studies. The study of the bacterial diversity, inside and outside the caves, indicates that the air is mostly populated by bacteria thriving in the subterranean environment. In addition, the diversity seems to be related with the presence of abundant phototrophic biofilms, but not with the number of visitors received by each cave.

Microbiological exploration of the Cueva del Viento lava tube system in Tenerife, Canary Islands

“…Forty‐two bacterial strains were isolated by culture techniques from the microbial mats collected in the Cueva del Viento lava tube system (Table S1 ). The mainly isolated strains belonged to the phyla Actinomycetota (43%) and Bacillota (41%) in agreement with the findings from other worldwide caves (Dominguez‐Moñino et al, 2021 ; Groth et al, 1999 ; Urzì et al, 2010 ). The phylum Pseudomonadota (12%) was observed in the 7G‐yellow and 11K‐white biofilm samples.…”

“…The results obtained using molecular and traditional tools show disparity in terms of the major groups found in subterranean environments. With traditional isolation techniques, the most abundant microorganisms were members of the Actinomycetota and Bacillota phyla (Dominguez‐Moñino et al, 2021 ; Groth et al, 1999 ; Urzì et al, 2010 ), while the molecular approaches revealed the existence of different and specific phyla promoted by the microenvironment (De Mandal et al, 2017 ; Gonzalez‐Pimentel et al, 2018 ; Saiz‐Jimenez, 2012 ).…”

Early Detection of Phototrophic Biofilms in the Polychrome Panel, El Castillo Cave, Spain

“…In a study on the aerobiology of three Andalusian caves (Ardales, Tesoro and Gruta de las Maravillas), 19 species of Streptomyces were identified. This diversity was directly related by Dominguez-Moñino et al [53] to the abundance of phototrophic biofilms, as is the case in the ground sample.…”

“…Phyllobacterium is a genus of Hyphomicrobiales frequently isolated from root nodules [50], although it is also found in subterranean environments, such as Phyllobacterium catacumbae, isolated from a Roman catacomb [51]. Species of Phyllobacterium have been collected in the air of caves, such as Lascaux [52] and Ardales [53]. Likewise, different species of Phyllobacterium were found in an Etruscan tomb [54].…”

“…In El Castillo Cave, Paenibacillus had important relative abundances in CAS1A (11.7%) and CAS3C (6.1%) and was absent in CAS4D and CAS6F; in the CAS2B it only reached 0.6% of relative abundance. Paenibacillus has been found in many Spanish caves, such as Altamira [74,75], Ardales, Tesoro and Gruta de las Maravillas [53] and is generally observed to be together with Bacillus. Bacillus was only present in samples CAS3C (3.9%) and CAS2B (1.0%).…”