Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory

ABSTRACT To assess the microbiology and corrosion potential of engineered components of a deep geological repository for long-term storage of high-level nuclear waste, the Materials Corrosion Test is being conducted at the Underground Research Laboratory in Grimsel, Switzerland. Modules containing m...

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Autores principales:	Katja Engel, Sian E. Ford, Sara Coyotzi, Jennifer McKelvie, Nikitas Diomidis, Greg Slater, Josh D. Neufeld
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	MX-80 bentonite clay nuclear waste disposal microbial characterization 16S rRNA gene sequencing Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/b633513a5bda44a8a7237a426c57056f
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spelling	oai:doaj.org-article:b633513a5bda44a8a7237a426c57056f2021-11-15T15:22:24ZStability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory10.1128/mSphere.00601-192379-5042https://doaj.org/article/b633513a5bda44a8a7237a426c57056f2019-12-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSphere.00601-19https://doaj.org/toc/2379-5042ABSTRACT To assess the microbiology and corrosion potential of engineered components of a deep geological repository for long-term storage of high-level nuclear waste, the Materials Corrosion Test is being conducted at the Underground Research Laboratory in Grimsel, Switzerland. Modules containing metal coupons surrounded by highly compacted MX-80 bentonite, at two dry densities (1.25 and 1.50 g/cm3), were emplaced within 9-m-deep boreholes, and the first modules were retrieved after 13 months of exposure. Bentonite and associated module materials were sampled, and microbial communities and their distributions were assessed using 16S rRNA gene sequencing and phospholipid fatty acid (PLFA) analysis. Borehole fluid was dominated by amplicon sequence variants (ASVs) affiliated with Desulfosporosinus and Desulfovibrio, which are putatively involved in sulfate reduction. The relative abundance of these ASVs was lower for samples from inside the borehole module, and they were almost undetectable in samples of the inner bentonite layer. The dominant ASV in case and filter sample sequence data was affiliated with Pseudomonas stutzeri, yet its relative abundance decreased in the inner layer samples. Streptomyces sp. ASVs were relatively abundant in all bentonite core sample data both prior to emplacement and after 13 months of exposure, presumably as metabolically inactive spores or extracellular “relic” DNA. PLFA concentrations in outer and inner layer bentonite samples suggested cellular abundances of 1 × 106 to 3 × 106 cells/g, with similar PLFA distributions within all bentonite samples. Our results demonstrate consistent microbial communities inside the saturated borehole module, providing the first evidence for microbial stability under conditions that mimic a deep geological repository. IMPORTANCE The Materials Corrosion Test in Grimsel Underground Research Laboratory, Switzerland, enables an evaluation of microbiological implications of bentonite clay at densities relevant for a deep geological repository. Our research demonstrates that after 13 months of exposure within a granitic host rock, the microbial 16S rRNA gene signatures of saturated bentonite clay within the modules were consistent with the profiles in the original clay used to pack the modules. Such results provide evidence that densities chosen for this emplacement test are refractory to microbial activity, at least on the relatively short time frame leading to the first time point sampling event, which will help inform in situ engineered barrier system science. This study has important implications for the design of deep geological repository sites under consideration for the Canadian Shield.Katja EngelSian E. FordSara CoyotziJennifer McKelvieNikitas DiomidisGreg SlaterJosh D. NeufeldAmerican Society for MicrobiologyarticleMX-80bentoniteclaynuclear waste disposalmicrobial characterization16S rRNA gene sequencingMicrobiologyQR1-502ENmSphere, Vol 4, Iss 6 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	MX-80 bentonite clay nuclear waste disposal microbial characterization 16S rRNA gene sequencing Microbiology QR1-502
spellingShingle	MX-80 bentonite clay nuclear waste disposal microbial characterization 16S rRNA gene sequencing Microbiology QR1-502 Katja Engel Sian E. Ford Sara Coyotzi Jennifer McKelvie Nikitas Diomidis Greg Slater Josh D. Neufeld Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
description	ABSTRACT To assess the microbiology and corrosion potential of engineered components of a deep geological repository for long-term storage of high-level nuclear waste, the Materials Corrosion Test is being conducted at the Underground Research Laboratory in Grimsel, Switzerland. Modules containing metal coupons surrounded by highly compacted MX-80 bentonite, at two dry densities (1.25 and 1.50 g/cm3), were emplaced within 9-m-deep boreholes, and the first modules were retrieved after 13 months of exposure. Bentonite and associated module materials were sampled, and microbial communities and their distributions were assessed using 16S rRNA gene sequencing and phospholipid fatty acid (PLFA) analysis. Borehole fluid was dominated by amplicon sequence variants (ASVs) affiliated with Desulfosporosinus and Desulfovibrio, which are putatively involved in sulfate reduction. The relative abundance of these ASVs was lower for samples from inside the borehole module, and they were almost undetectable in samples of the inner bentonite layer. The dominant ASV in case and filter sample sequence data was affiliated with Pseudomonas stutzeri, yet its relative abundance decreased in the inner layer samples. Streptomyces sp. ASVs were relatively abundant in all bentonite core sample data both prior to emplacement and after 13 months of exposure, presumably as metabolically inactive spores or extracellular “relic” DNA. PLFA concentrations in outer and inner layer bentonite samples suggested cellular abundances of 1 × 106 to 3 × 106 cells/g, with similar PLFA distributions within all bentonite samples. Our results demonstrate consistent microbial communities inside the saturated borehole module, providing the first evidence for microbial stability under conditions that mimic a deep geological repository. IMPORTANCE The Materials Corrosion Test in Grimsel Underground Research Laboratory, Switzerland, enables an evaluation of microbiological implications of bentonite clay at densities relevant for a deep geological repository. Our research demonstrates that after 13 months of exposure within a granitic host rock, the microbial 16S rRNA gene signatures of saturated bentonite clay within the modules were consistent with the profiles in the original clay used to pack the modules. Such results provide evidence that densities chosen for this emplacement test are refractory to microbial activity, at least on the relatively short time frame leading to the first time point sampling event, which will help inform in situ engineered barrier system science. This study has important implications for the design of deep geological repository sites under consideration for the Canadian Shield.
format	article
author	Katja Engel Sian E. Ford Sara Coyotzi Jennifer McKelvie Nikitas Diomidis Greg Slater Josh D. Neufeld
author_facet	Katja Engel Sian E. Ford Sara Coyotzi Jennifer McKelvie Nikitas Diomidis Greg Slater Josh D. Neufeld
author_sort	Katja Engel
title	Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
title_short	Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
title_full	Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
title_fullStr	Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
title_full_unstemmed	Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory
title_sort	stability of microbial community profiles associated with compacted bentonite from the grimsel underground research laboratory
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/b633513a5bda44a8a7237a426c57056f
work_keys_str_mv	AT katjaengel stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT sianeford stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT saracoyotzi stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT jennifermckelvie stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT nikitasdiomidis stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT gregslater stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory AT joshdneufeld stabilityofmicrobialcommunityprofilesassociatedwithcompactedbentonitefromthegrimselundergroundresearchlaboratory
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Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory

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