The potential risk to humans from incidental ingestion of As-contaminated soil and mine waste is influenced by the mineralogical composition of the As phases present. Using the Solubility Bioaccessibility Research Consortium in vitro assay, simulating gastric conditions, we determined the oral bioaccessibility of As in 16 environmentally important As mineral(oid)s commonly found in mine waste and contaminated soils. Our results revealed a wide range of bioaccessibility values closely related to the solubility of the mineral(oid)s. Bioaccessibility values ranged from 0.15 % in minerals with great environmental stability such as scorodite and pharmacosiderite, to complete (100 %) release from minerals such as adamite, erythrite and pharmacolite. Intermediate bioaccessibility levels were observed in minerals such as arsenolite and yukonite, ranging from 6 % to 67 %. In mixtures with soil, the bioaccessibility of As in mineral(oid)s with low solubility was significantly reduced, with bioaccessibility values up to 8.7 times lower due to the effective adsorption of As by the soil. We conclude that the bioaccessibility of As in natural soil and mine waste is intricately influenced by both the mineralogical composition of As phases and the As retention capacity of natural materials under acidic conditions of gastric fluids.
- Klíčová slova
- Arsenic, Bioaccessibility, Mineral(oid)s, Soil, Solubility,
- MeSH
- arsen * analýza chemie MeSH
- biologická dostupnost * MeSH
- hornictví * MeSH
- látky znečišťující půdu * analýza chemie farmakokinetika MeSH
- lidé MeSH
- minerály * chemie MeSH
- rozpustnost * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- arsen * MeSH
- látky znečišťující půdu * MeSH
- minerály * MeSH
Today, the biodiversity of endolithic microbial colonisations are only partly understood. In this study, we used a combination of molecular community metabarcoding using the 16S rRNA gene, light microscopy, CT-scan analysis, and Raman spectroscopy to describe gypsum endolithic communities in 2 sites-southern Poland and northern Israel. The obtained results have shown that despite different geographical areas, climatic conditions, and also physical features of colonized gypsum outcrops, both of these sites have remarkably similar microbial and pigment compositions. Cyanobacteria dominate both of the gypsum habitats, followed by Chloroflexi and Pseudomonadota. Among cyanobacteria, Thermosynechococcaceae were more abundant in Israel while Chroococcidiopsidaceae in Poland. Interestingly, no Gloeobacteraceae sequences have been found in Poland, only in Israel. Some of the obtained 16S rRNA gene sequences of cyanobacteria matched previously detected sequences from endolithic communities in various substrates and geographical regions, supporting the hypothesis of global metacommunity, but more data are still needed. Using Raman spectroscopy, cyanobacterial UV-screening pigments-scytonemin and gloeocapsin have been detected alongside carotenoids, chlorophyll a and melanin. These pigments can serve as potential biomarkers for basic taxonomic identification of cyanobacteria. Overall, this study provides more insight into the diversity of cyanobacterial endolithic colonisations in gypsum across different areas.
- Klíčová slova
- 16S rRNA, Cyanobacteria, Endoliths, Gypsum, Metacommunity, Phototrophs,
- MeSH
- mikrobiota MeSH
- RNA ribozomální 16S genetika MeSH
- sinice * genetika metabolismus klasifikace MeSH
- síran vápenatý * chemie MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Geografické názvy
- Izrael MeSH
- Polsko MeSH
- Názvy látek
- RNA ribozomální 16S MeSH
- síran vápenatý * MeSH
This study utilized X-ray micro-computed tomography (micro-CT) to investigate weathered gypsum rocks which can or do serve as a rock substrate for endolithic organisms, focusing on their internal pore-fracture microstructure, estimating porosity, and quantitative comparison between various samples. Examining sections and reconstructed 3D models provides a more detailed insight into the overall structural conditions within rock fragments and the interconnectivity in pore networks, surpassing the limitations of analyzing individual 2D images. Results revealed diverse gypsum forms, cavities, fractures, and secondary features influenced by weathering. Using deep learning segmentation based on the U-Net models within the Dragonfly software enabled to identify and visualize the porous systems and determinate void space which was used to calculate porosity. This approach allowed to describe what type of microstructures and cavities is responsible for the porous spaces in different gypsum samples. A set of quantitative analysis of the detected void and modeled networks provided a needed information about the development of the pore system, connectivity, and pore size distribution. Comparison with mercury intrusion porosimetry showed that both methods consider different populations of pores. In our case, micro-CT typically detects larger pores (> 10 μm) which is related to the effective resolution of the scanned images. Still, micro-CT demonstrated to be an efficient tool in examining the internal microstructures of weathered gypsum rocks, with promising implications particularly in geobiology and microbiology for the characterization of lithic habitats.
- Klíčová slova
- Deep learning, Gypsum, Micro-CT, Porosity, Segmentation, U-net, Weathering,
- Publikační typ
- časopisecké články MeSH
In this study, we used microscopic, spectroscopic, and molecular analysis to characterize endolithic colonization in gypsum (selenites and white crystalline gypsum) from several sites in Sicily. Our results showed that the dominant microorganisms in these environments are cyanobacteria, including: Chroococcidiopsis sp., Gloeocapsopsis pleurocapsoides, Gloeocapsa compacta, and Nostoc sp., as well as orange pigmented green microalgae from the Stephanospherinia clade. Single cell and filament sequencing coupled with 16S rRNA amplicon metagenomic profiling provided new insights into the phylogenetic and taxonomic diversity of the endolithic cyanobacteria. These organisms form differently pigmented zones within the gypsum. Our metagenomic profiling also showed differences in the taxonomic composition of endoliths in different gypsum varieties. Raman spectroscopy revealed that carotenoids were the most common pigments present in the samples. Other pigments such as gloeocapsin and scytonemin were also detected in the near-surface areas, suggesting that they play a significant role in the biology of endoliths in this environment. These pigments can be used as biomarkers for basic taxonomic identification, especially in case of cyanobacteria. The findings of this study provide new insights into the diversity and distribution of phototrophic microorganisms and their pigments in gypsum in Southern Sicily. Furthemore, this study highlights the complex nature of endolithic ecosystems and the effects of gypsum varieties on these communities, providing additional information on the general bioreceptivity of these environments.
- Klíčová slova
- cyanobacteria, endoliths, green algae, gypsum, metagenomics, phototrophs,
- Publikační typ
- časopisecké články MeSH
Organic minerals occur rather rarely in some types of peat bogs, sedimentary geological environments, and hydrothermal veins. Commonly, calcium oxalates are produced by several plants, terpenoids are often associated with conifers. Because of the organic precursor, these minerals, from the smallest group of the mineralogical system, are sometimes considered as biomarkers. Potential detection of these compounds has high relevance in the fields of exobiology or geobiology. Here we show the potential of four portable Raman spectrometers, using different excitation wavelengths and technologies (operating at 532, 785, and 1064nm together with an advanced spectrometer using the sequentially shifted excitation (SSE) technology), for the rapid and non-destructive identification of these phases. For the organic minerals investigated here, the most intense Raman bands are generally detected at the expected wavenumber positions ±1-4cm-1 in the region 100-2000cm-1 in the spectra obtained from all spectrometers. Additionally, two spectrometers (the 532nm instrument and the SSE) are capable of detecting Raman bands in the higher wavenumber shift region of 2000-3500cm-1, allowing the more detailed characterization and differentiation of the related phases. From this work, and on the basis of the experimental data obtained, it is clear that the longer laser excitation wavelengths are more preferable for organic minerals identification due to the better mitigation of fluorescence emission. In contrast, the Raman spectrometer equipped with the shortest excitation wavelength (532nm) gives a significantly higher spectral resolution and a more detailed discrimination of the Raman bands, provided that the conditions of general lower level of fluorescence emission are met. The results presented in the current study complement the knowledge on minerals and biomarkers of relevance for Martian environments which have been measured with mobile Raman spectrometers. The outcome creates a solid base towards the use of lightweight mobile Raman systems that can be used outdoors and on terrestrial outcrops. Moreover, these results and conclusions are of use for the further development of dedicated spectrometers destined for the instrumental suites on planetary rovers, in the frame of the forthcoming exobiology focused missions to Mars to be launched by NASA and ESA.
- Klíčová slova
- Dispersive 1064nm Raman spectrometer, Exobiology, Organic minerals, Portable Raman spectroscopy, Sequentially shifted excitation,
- Publikační typ
- časopisecké články MeSH
Inclusions in evaporitic minerals sometimes contain remnants of microorganisms or biomarkers, which can be considered as traces of life. Raman spectroscopy with resonance enhancement is one of the best analytical methods to search for such biomarkers in places of interest for astrobiology, including the surface and near subsurface of planet Mars. Portable Raman spectrometers are used as training tools for detection of biomarkers. Investigations of the limits and challenges of detecting biomolecules in crystals using Raman spectroscopy is important because natural occurrences often involve mineral assemblages as well as their fluid and solid inclusions. A portable Raman spectrometer with 532 nm excitation was used for detection of carotenoid biomarkers: salinixanthin of Salinibacter ruber (Bacteroidetes) and α-bacterioruberin of Halorubrum sodomense (Halobacteria) in laboratory-grown artificial inclusions in compound crystals of several chlorides and sulfates, simulating entrapment of microorganisms in evaporitic minerals. Crystals of halite (NaCl), sylvite (KCl), arcanite (K2SO4) and tschermigite ((NH4)Al(SO4)2·12H2O) were grown from synthetic solutions that contained microorganisms. A second crystalline layer of NaCl or K2SO4 was grown subsequently so that primary crystals containing microorganisms are considered as solid inclusions. A portable Raman spectrometer with resonance enabling excitation detected signals of both carotenoid pigments. Correct positions of diagnostic Raman bands corresponding to the specific carotenoids were recorded.
- Klíčová slova
- carotenoids, halophilic prokaryotes, inclusions, miniature Raman spectrometer, salts,
- MeSH
- Bacteria chemie MeSH
- chloridy chemie MeSH
- exobiologie * MeSH
- karotenoidy analýza MeSH
- krystalizace MeSH
- Mars * MeSH
- prokaryotické buňky chemie MeSH
- Ramanova spektroskopie přístrojové vybavení MeSH
- sírany chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chloridy MeSH
- karotenoidy MeSH
- sírany MeSH
