Analytical pyrolysis and stable isotope analyses reveal past environmental changes in coralloid speleothems from Easter Island (Chile)

Miller, Ana Z.; Rosa, José M. de la; Morillo, N. T. Jiménez; Pereira, M.F.C.; González‐Pérez, José Antonío; Calaforra, J. M.; Sáiz‐Jiménez, Cesáreo

doi:10.1016/j.chroma.2016.07.038

Cited by 21 publications

(27 citation statements)

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“…The XRD pattern of the coralloids displayed the typical broad diffuse band centered at about 23.4° 2 θ (3.75 Å) of opal-A (SiO 2 . n H 2 0) 21 , 22 , with overlapped reflections attributed to hydrated halloysite, Al 2 Si 2 O 5 (OH) 4 .2H 2 O 23 (Fig. 4A ).…”

Section: Resultsmentioning

confidence: 99%

“…Yellow microbial mats covering coralloid speleothems in EP01 lava tube from La Palma Island (Spain) were investigated and compared with yellow and white microbial mats from Azores lava tubes (Portugal). Coralloid speleothems are commonly found either on the surface of basaltic lava caves or in limestone caves 22 , 31 . They are defined as a variety of white to grey to dark brown nodular, globular, botryoidal or coral-like speleothems 31 .…”

Section: Discussionmentioning

confidence: 99%

“…They are defined as a variety of white to grey to dark brown nodular, globular, botryoidal or coral-like speleothems 31 . Their mineralogy has been described as amorphous silica, mainly opal-A 22 , 32 , and their genesis has been interpreted as microbially-mediated 21 , 25 , 33 . Mineralogically, the yellowish coralloids from EP01 lava tube are almost entirely formed by amorphous opal-A and minor contribution of halloysite.…”

Section: Discussionmentioning

confidence: 99%

“…2 ). It is well known that the amount of water entering into a cave determines speleothem growth and composition due to water-rock interactions 22 , 25 . The presence of halloysite in the yellowish coralloid speleothems from La Palma is probably related to weathering processes of volcanic rocks 34 , 35 and indicates that the genesis of the coralloids have a close relationship with the water-rock interactions in the EP01 lava tube.…”

Section: Discussionmentioning

confidence: 99%

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Yellow coloured mats from lava tubes of La Palma (Canary Islands, Spain) are dominated by metabolically active Actinobacteria

Gonzalez-Pimentel

Miller

Jurado

et al. 2018

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Microbial diversity in lava tubes from Canary Islands (Spain) has never been explored thus far offering a unique opportunity to study subsurface microbiology. Abundant yellow coloured mats developing on coralloid speleothems in a lava tube from La Palma Islands were studied by next-generation sequencing and DNA/RNA clone library analyses for investigating both total and metabolically active bacteria. In addition, morphological and mineralogical characterization was performed by field emission scanning electron microscopy (FESEM), micro-computed tomography, X-ray diffraction and infrared spectroscopy to contextualize sequence data. This approach showed that the coralloid speleothems consist of banded siliceous stalactites composed of opal-A and hydrated halloysite. Analytical pyrolysis was also conducted to infer the possible origin of cave wall pigmentation, revealing that lignin degradation compounds can contribute to speleothem colour. Our RNA-based study showed for the first time that members of the phylum Actinobacteria, with 55% of the clones belonging to Euzebyales order, were metabolically active components of yellow mats. In contrast, the DNA clone library revealed that around 45% of clones were affiliated to Proteobacteria. Composition of microbial phyla obtained by NGS reinforced the DNA clone library data at the phylum level, in which Proteobacteria was the most abundant phylum followed by Actinobacteria.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Yellow coloured mats from lava tubes of La Palma (Canary Islands, Spain) are dominated by metabolically active Actinobacteria

Gonzalez-Pimentel

Miller

Jurado

et al. 2018

Sci Rep

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“…Chemical analyses of lichen thalli were carried out by direct pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) using a double-shot pyrolyser (Frontier Laboratories, model 2020i) attached to a GC/MS Agilent 6890N as described in Miller et al ( 2016 ). One milligram each of C. gyrosa samples from the control, niche-led conditions, and exposed-to-full UV sets were placed in small crucible capsules and introduced into a pre-heated micro-furnace at 500°C for 1 min.…”

Section: Methodsmentioning

confidence: 99%

Cellular Responses of the Lichen Circinaria gyrosa in Mars-Like Conditions

et al. 2018

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Lichens are extremely resistant organisms that colonize harsh climatic areas, some of them defined as “Mars-analog sites.” There still remain many unsolved questions as to how lichens survive under such extreme conditions. Several studies have been performed to test the resistance of various lichen species under space and in simulated Mars-like conditions. The results led to the proposal that Circinaria gyrosa (Lecanoromycetes, Ascomycota) is one of the most durable astrobiological model lichens. However, although C. gyrosa has been exposed to Mars-like environmental conditions while in a latent state, it has not been exposed in its physiologically active mode. We hypothesize that the astrobiological test system “Circinaria gyrosa,” could be able to be physiologically active and to survive under Mars-like conditions in a simulation chamber, based on previous studies performed at dessicated-dormant stage under simulated Mars-like conditions, that showed a complete recover of the PSII activity (Sánchez et al., 2012). Epifluorescence and confocal laser scanning microscopy (CLSM) showed that living algal cells were more abundant in samples exposed to niche conditions, which simulated the conditions in micro-fissures and micro-caves close to the surface that have limited scattered or time-dependent light exposure, than in samples exposed to full UV radiation. The medulla was not structurally affected, suggesting that the niche exposure conditions did not disturb the lichen thalli structure and morphology as revealed by field emission scanning electron microscopy (FESEM). In addition, changes in the lichen thalli chemical composition were determined by analytical pyrolysis. The chromatograms resulting from analytical pyrolysis at 500°C revealed that lichen samples exposed to niche conditions and full UV radiation consisted primarily of glycosidic compounds, lipids, and sterols, which are typical constituents of the cell walls. However, specific differences could be detected and used as markers of the UV-induced damage to the lichen membranes. Based on its viability responses after rehydration, our study shows that the test lichen survived the 30-day incubation in the Mars chamber particularly under niche conditions. However, the photobiont was not able to photosynthesize under the Mars-like conditions, which indicates that the surface of Mars is not a habitable place for C. gyrosa.

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First Insights into the Bacterial Diversity of Mount Etna Volcanic Caves

et al. 2023

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While microbial communities in limestone caves across the world are relatively understood, knowledge of the microbial composition in lava tubes is lagging behind. These caves are found in volcanic regions worldwide and are typically lined with multicolored microbial mats on their walls and ceilings. The Mount Etna (Sicily, S-Italy) represents one of the most active volcanos in the world. Due to its outstanding biodiversity and geological features, it was declared Natural Heritage of Humanity by the UNESCO in 2013. Despite the presence of more than 200 basaltic lava tubes, the microbial diversity of these hypogean systems has never been investigated so far. Here, we investigated bacterial communities in four lava tubes of Mount Etna volcano. Field emission scanning electron microscopy (FESEM) was carried out for the morphological characterization and detection of microbial features. We documented an abundant presence of microbial cells with different morphotypes including rod-shaped, filamentous, and coccoidal cells with surface appendages, resembling actinobacteria reported in other lava tubes across the world. Based on 16S rRNA gene analysis, the colored microbial mats collected were mostly composed of bacteria belonging to the phyla Actinomycetota, Pseudomonadota, Acidobacteriota, Chloroflexota, and Cyanobacteria. At the genus level, the analysis revealed a dominance of the genus Crossiella, which is actively involved in biomineralization processes, followed by Pseudomonas, Bacillus, Chujaibacter, and Sphingomonas. The presence of these taxa is associated with the carbon, nitrogen, and ammonia cycles, and some are possibly related to the anthropic disturbance of these caves. This study provides the first insight into the microbial diversity of the Etna volcano lava tubes, and expands on previous research on microbiology of volcanic caves across the world.

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Analytical pyrolysis and stable isotope analyses reveal past environmental changes in coralloid speleothems from Easter Island (Chile)

Cited by 21 publications

References 78 publications

Yellow coloured mats from lava tubes of La Palma (Canary Islands, Spain) are dominated by metabolically active Actinobacteria

Yellow coloured mats from lava tubes of La Palma (Canary Islands, Spain) are dominated by metabolically active Actinobacteria

Cellular Responses of the Lichen Circinaria gyrosa in Mars-Like Conditions

First Insights into the Bacterial Diversity of Mount Etna Volcanic Caves

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