Bacterial Diversity in the Hyperalkaline Allas Springs (Cyprus), a Natural Analogue for Cementitious Radioactive Waste Repository

Rizoulis, Athanasios; Milodowski, Antoni E.; Morris, Katherine; Lloyd, Jonathan R.

doi:10.1080/01490451.2014.961107

Cited by 29 publications

(15 citation statements)

References 65 publications

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“…A key constraint appears to be the presence of organisms from the genus Alkaliphilus within the consortia; their absence confines the fermentation of ISAs to a pH of ≤10.0. Members of this genus have been detected in anthropogenic hyper alkaline sites [ 27 , 60 ] where in-situ ISA formation has been observed [ 28 ] and in natural hyperalkaline systems[ 61 ]. As pH increases methane generation becomes confined to the hydrogenotrophic pathway due to the loss of acetoclastic methanogens, resulting in the accumulation of acetic acid.…”

Section: Discussionmentioning

confidence: 99%

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

et al. 2015

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One design concept for the long-term management of the UK’s intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.013.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

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Section: Discussionmentioning

confidence: 99%

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

et al. 2015

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“…The most abundant organism in the MP and SP areas in this study were affiliated with the genus Hydrogenophaga (35.61 ± 9.42%), which comprise aerobic, chemoorganotrophic organisms that use hydrogen as an energy source (Willems et al, 1989;Kampfer et al, 2005;Yoon et al, 2008). Members of genus Hydrogenophaga are present in a variety of natural and engineered (e.g., waste water) environments (Lambo and Patel, 2006;Fahy et al, 2008;Yoon et al, 2008;Schwartz et al, 2013), including hyper alkaline sites such as Allas Springs, Cyprus where the pH was 11.9, similar to the alkaline conditions to the INP waters (pH 11.6) (Rizoulis et al, 2016) and serpentinizing springs (pH 11.6, The Cedars, Los Angeles, CA, United States) (Suzuki et al, 2014). The presence of Hydrogenophaga as a key microbial component during all the sampling times suggests that the metabolism of H 2 may be occurring within the pond, which is of particular interest since oxidation of hydrogen could also be linked to the reduction of a range of electron acceptors, including radionuclides (Lloyd, 2003).…”

Section: Discussionmentioning

confidence: 99%

Identification of a Stable Hydrogen-Driven Microbiome in a Highly Radioactive Storage Facility on the Sellafield Site

et al. 2020

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The use of nuclear power has been a significant part of the United Kingdom’s energy portfolio with the Sellafield site being used for power production and more recently reprocessing and decommissioning of spent nuclear fuel activities. Before being reprocessed, spent nuclear fuel is stored in water ponds with significant levels of background radioactivity and in high alkalinity (to minimize fuel corrosion). Despite these challenging conditions, the presence of microbial communities has been detected. To gain further insight into the microbial communities present in extreme environments, an indoor, hyper-alkaline, oligotrophic, and radioactive spent fuel storage pond (INP) located on the Sellafield site was analyzed. Water samples were collected from sample points within the INP complex, and also the purge water feeding tank (FT) that supplies water to the pond, and were screened for the presence of the 16S and 18S rRNA genes to inform sequencing requirements over a period of 30 months. Only 16S rRNA genes were successfully amplified for sequencing, suggesting that the microbial communities in the INP were dominated by prokaryotes. Quantitative Polymerase Chain Reaction (qPCR) analysis targeting 16S rRNA genes suggested that bacterial cells in the order of 104–106 mL–1 were present in the samples, with loadings rising with time. Next generation Illumina MiSeq sequencing was performed to identify the dominant microorganisms at eight sampling times. The 16S rRNA gene sequence analysis suggested that 70% and 91% from of the OTUs samples, from the FT and INP respectively, belonged to the phylum Proteobacteria, mainly from the alpha and beta subclasses. The remaining OTUs were assigned primarily to the phyla Acidobacteria, Bacteroidetes, and, Cyanobacteria. Overall the most abundant genera identified were Hydrogenophaga, Curvibacter, Porphyrobacter, Rhodoferax, Polaromonas, Sediminibacterium, Roseococcus, and Sphingomonas. The presence of organisms most closely related to Hydrogenophaga species in the INP areas, suggests the metabolism of hydrogen as an energy source, most likely linked to hydrolysis of water caused by the stored fuel. Isolation of axenic cultures using a range of minimal and rich media was also attempted, but only relatively minor components (from the phylum Bacteroidetes) of the pond water communities were obtained, emphasizing the importance of DNA-based, not culture-dependent techniques, for assessing the microbiome of nuclear facilities.

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“…In addition, 100 ml of the spring water sample was filtered through 47 mm Whatman sterile membrane filters to concentrate the biomass; DNA was extracted from the biomass using the DNeasy PowerWater Kit (Qiagen, Manchester, United Kingdom). The 16S rRNA gene was amplified via PCR (polymerase chain reaction) using 8F (5 -AGAG TTTGATCCTGGCTCAG-3 ), and 1492R (5 -TACGGYTACCT TGTTACGACTT-3 ) primers using the methods of Rizoulis et al (2016). The primer pair 8F-1492R was purely used to check that the DNA extraction procedure had isolated DNA containing the bacterial 16S rRNA gene, prior to sequencing reactions being carried out on the samples.…”

Section: Dna Extractionmentioning

confidence: 99%

A Novel “Microbial Bait” Technique for Capturing Fe(III)-Reducing Bacteria

et al. 2020

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Microbial reduction of Fe(III) is a key geochemical process in anoxic environments, controlling the degradation of organics and the mobility of metals and radionuclides. To further understand these processes, it is vital to develop a reliable means of capturing Fe(III)-reducing microorganisms from the field for analysis and lab-based investigations. In this study, a novel method of capturing Fe(III)-reducing bacteria using Fe(III)-coated pumice "microbe-baits" was demonstrated. The methodology involved the coating of pumice (approximately diameter 4 to 6 mm) with a bioavailable Fe(III) mineral (akaganeite), and was verified by deployment into a freshwater spring for 2 months. On retrieval, the coated pumice baits were incubated in a series of lab-based microcosms, amended with and without electron donors (lactate and acetate), and incubated at 20 • C for 8 weeks. 16S rRNA gene sequencing using the Illumina MiSeq platform showed that the Fe(III)-coated pumice baits, when incubated in the presence of lactate and acetate, enriched for Deltaproteobacteria (relative abundance of 52% of the sequences detected corresponded to Geobacter species and 24% to Desulfovibrio species). In the absence of added electron donors, Betaproteobacteria were the most abundant class detected, most heavily represented by a close relative to Rhodoferax ferrireducens (15% of species detected), that most likely used organic matter sequestered from the spring waters to support Fe(III) reduction. In addition, TEM-EDS analysis of the Fe(III)-coated pumice slurries amended with electron donors revealed that a biogenic Fe(II) mineral, magnetite, was formed at the end of the incubation period. These results demonstrate that Fe(III)-coated pumice "microbe baits" can potentially help target metal-reducing bacteria for culture-dependent studies, to further our understanding of the nano-scale microbe-mineral interactions in aquifers.

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Bacterial Diversity in the Hyperalkaline Allas Springs (Cyprus), a Natural Analogue for Cementitious Radioactive Waste Repository

Cited by 29 publications

References 65 publications

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

Identification of a Stable Hydrogen-Driven Microbiome in a Highly Radioactive Storage Facility on the Sellafield Site

A Novel “Microbial Bait” Technique for Capturing Fe(III)-Reducing Bacteria

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