Biological Control of Phototrophic Biofilms in a Show Cave: The Case of Nerja Cave

13 páginas.- 5 figuras.- 2 tablas.- 39 referenciasCyanobacteria and microalgae are usually found in speleothems, rocks and walls of show caves exposed to artificial lighting. These microorganisms develop as biofilms coating the mineral surfaces and producing aesthetic, physical and chemical deterioration. A wide number of physical, chemical and environmental-friendly methods have been used for controlling the biofilms with different results. Natural biological control has been suggested by some authors as a theoretical approach but without direct evidence or application. Here we report the finding of a natural biological control of phototrophic biofilms on the speleothems of Nerja Cave, Malaga, Spain. The formation of plaques or spots where the phototrophic microorganisms disappeared can be assumed on the basis of processes of predation of bacteria, amoebas and some other organisms on the phototrophic biofilms. This study aims at investigating the potentialities of the biological control of phototrophic biofilms in caves, but the originality of these data should be confirmed in future studies with a larger number of biofilm samples in different ecological scenarios.Peer reviewe

Microbiology of the stalactites from Grotta dei Cervi, Porto Badisco, Italy

The active stalactites from Grotta dei Cervi, Porto Badisco, southeastern Italy, were sampled to investigate the microbial communities present in these speleothems. Sampling was carried out in a transect about 150 m long in the central gallery, where numerous Gram-positive bacteria were isolated. Actinomycetes of the genus Streptomyces were the most abundant, followed by members of the genus Bacillus. Further isolates were assigned to the genera Amycolatopsis, Arthrobacter, Agromyces, Micrococcus, Nocardiopsis and Rhodococcus of the order Actinomycetales. The ability of actinomycetes to colonize subterranean environments is discussed

Streptomyces benahoarensis sp. nov. Isolated From a Lava Tube of La Palma, Canary Islands, Spain

10 páginas.- 3 figuras.- 2 tablas.- 51 referencias.- The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2022.907816/full#supplementary-materialTwo Streptomyces strains, labeled as MZ03-37(T) and MZ03-48, were isolated from two different samples, a mucolite-type speleothem and a microbial mat on the walls of a lava tube from La Palma Island (Canary Islands). Phylogenetic analysis based on concatenated sequences of six housekeeping genes indicated that both strains belonged to the same species. The closest relatives for both strains were Streptomyces palmae CMU-AB204(T) (98.71%), Streptomyces catenulae NRRL B-2342(T) (98.35%), and Streptomyces ramulosus NRRL B-2714(T) (98.35%). Multi-locus sequence analysis (MLSA), based on five house-keeping gene alleles (i.e., atpD, gyrB, recA, rpoB, and trpB), indicated that both isolated strains were closely related to S. catenulae NRRL B-2342(T). Whole-genome average nucleotide identity (ANI) scores of both strains were in the threshold value for species delineation with the closest species. Both strains presented a G+C content of 72.1 mol%. MZ03-37(T) was light brown in substrate and white in aerial mycelium, whereas MZ03-48 developed a black aerial and substrate mycelium. No pigment diffusion was observed in both strains. They grew at 10 degrees C-37 degrees C (optimum 28 degrees C-32 degrees C) and in the presence of up to 15% (w/v) NaCl. MZ03-37(T) grew at pH 5-10 (optimal 6-9), whereas MZ03-48 grew at pH 4-11 (optimal 5-10). LL-Diaminopimelic acid was the main diamino acid identified. The predominant fatty acids in both strains were iso-C-16:0, anteiso-C-15:0, C-16:0, and iso-C-14:0. The major isoprenoid quinones were MK-9(H6) and MK-9(H8), and the main polar lipids were aminolipid, phospholipid, and phosphoglycolipid. In silico analyses for functional annotation predicted the presence of gene clusters involved in resistome mechanisms and in the synthesis of described antimicrobials such as linocin-M18 and curamycin, as well as different genes likely involved in mechanisms for active compound synthesis, both already described and not discovered so far. On the basis of their phylogenetic relatedness and their phenotypic and genotypic features, the strains MZ03-37(T) and MZ03-48 represented a novel species within the genus Streptomyces, for which the name Streptomyces benahoarensis sp. nov. is proposed. The type strain is MZ03-37(T) (= CECT 9805 = DSMZ 8002); and MZ03-48 (= CECT 9806 = DSMZ 8011) is a reference strain.This study was supported by the project 0483_PROBIOMA_5_E, co-financed by the European Regional Development Fund within the framework of the Interreg V A Spain - Portugal program (POCTEP) 2014-2020. 2015 and 2016 field trips to the cave were supported by a former Spanish Ministry of Economy, Industry, and Competitiveness (MINEICO) project CGL2013-41674-PPeer reviewe

Analytical pyrolysis of the fungal melanins from Ochroconis spp. isolated from Lascaux Cave, France

Analytical pyrolysis is a tool widely used for investigating the nature of macromolecules. This technique has been applied with success for solving the chemical structure of geo- and biopolymers. However, with complex macromolecules, such as fungal melanins, analytical pyrolysis presents some drawbacks due to the fact that they rarely can be obtained in a pure grade and contains a mixture of polysaccharides, chitin, proteins, nucleic acids, and lipids, among other materials. Analytical pyrolysis permits the characterization of the compounds co-extracted or linked to the melanin. Nevertheless, our data revealed that under the conditions usually employed in the pyrolysis of melanins, the technique presented serious limitations due to the complex structure and diversity of components that suffer extensive thermal degradation through secondary reactions with the production of considerable number of artifacts. To the light of pyrolysis data, the melanin of Ochroconis spp. is not based on 3,4-dihydroxyphenylalanine (DOPA) or 1,8-dihydroxynaphthalene (DHN), and it is suggested that it could be a type of pyomelanin, based on the polymerization of homogentisic acid and other phenolic compounds

Pathogenic and opportunistic microorganisms in caves

With today’s leisure tourism, the frequency of visits to many caves makes it necessary to know about possible potentially pathogenic microorganisms in caves, determine their reservoirs, and inform the public about the consequences of such visits. Our data reveal that caves could be a potential danger to visitors because of the presence of opportunistic microorganisms, whose existence and possible development in humans is currently unknown

Pathogenic and opportunistic microorganisms in caves

With today’s leisure tourism, the frequency of visits to many caves makes it necessary to know about possible potentially pathogenic microorganisms in caves, determine their reservoirs, and inform the public about the consequences of such visits. Our data reveal that caves could be a potential danger to visitors because of the presence of opportunistic microorganisms, whose existence and possible development in humans is currently unknown

Las cuevas como recurso biotecnológico

12 páginas.- 5 figuras.- 2 tablas.- 39 referencias.- Comunicación oral presentada en el VIII Congreso Español sobre Cuevas y Minas Turísticas "Minas y Cuevas: Patrimonio Geológico y Turístico". J.M. Calaforra y J.J. Durán Valsero (eds.), Pulpí (Almería) 19-22 octubre 2022.- Enlace al libro de Actas completo https://www.cuevasturisticas.es/actas-cuevatur-2022Las cuevas vienen siendo estudiadas desde diversos puntos de vistas: ambiental, geológico, geoquímico, microbiológico, turístico, etc. Sin embargo, las cuevas y otros ambientes subterráneos han sido poco explorados desde el punto de vista biotecnológico, aunque representan nichos ecológicos indispensables que podrían ofrecer nuevas moléculas de interés para la medicina y la farmacología. Se han investigado las bacterias de diversas cuevas de la Península Ibérica, así como de las Islas Canarias para comprobar su bioactividad. Entre ellas, han mostrado un interesante potencial antimicrobiano algunas de las bacterias aisladas de la Cueva de Altamira. Los análisis in vitro e in silico mostraron la inhibición de bacterias patógenas Gram- positivas, Gram-negativas y hongos. El interés de esta investigación se apoya en la conocida resistencia de las bacterias patógenas a los antimicrobianos, lo que se ha convertido en un problema mundial en las últimas décadas. Nuestros datos muestran la presencia de bacterias productoras de compuestos antimicrobianos en ambientes subterráneos; y el estudio de sus genomas indicarían la existencia de genes implicados en la síntesis de nuevos compuestos. Palabras clave: Cueva de Altamira, compuestos antimicrobianos, Crossiella, Pseudomonas, predicción de genes.Esta publicación es parte del proyecto de investigación 0483_PROBIOMA_5_E.N

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

European caves contain some of the world’s greatest Paleolithic paintings, and their conservation is at risk due to the use of artificial lighting. Both lighting and high CO2 promotes the growth of phototrophic organisms on walls, speleothems and ground sediments. In addition, the combined effect of increases in CO2, vapor concentration and temperature variations induced by visitors can directly affect the development of corrosion processes on the cave rock surfaces. An early detection of the occurrence of phototrophic biofilms on Paleolithic paintings is of the utmost importance, as well as knowing the microorganisms involved in the colonization of rocks and walls. Knowledge of the colonizing species and their ecology will allow the adoption of control measures. However, this is not always possible due to the limited amount of biomass available for molecular analyses. Here, we present an alternative approach to study faint green biofilms of Chlorophyta in the initial stage of colonization on the Polychrome Panel in El Castillo Cave, Cantabria, Spain. The study of the biofilms collected on the rock art panel and in the ground sediments revealed that the lighting of the cave promoted the development of the green algae Jenufa and Coccomyxa, as well as of complex prokaryotic and eukaryotic communities, including amoebae, their endoparasites and associated bacteria and fungi. The enrichment method used is proposed as a tool to overcome technical constraints in characterizing biofilms in the early stages, allowing a preliminary characterization before deciding for direct or indirect interventions in the cave