Occurrence and identification of microorganisms in compacted clay-based buffer material designed for use in a nuclear fuel waste disposal vault

1997 ◽  
Vol 43 (12) ◽  
pp. 1133-1146 ◽  
Author(s):  
Simcha Stroes-Gascoyne ◽  
Shelley A. Haveman ◽  
Connie J. Hamon ◽  
Terri-Lynn Delaney ◽  
Karsten Pedersen ◽  
...  
Keyword(s):  
16S Rrna ◽  
Moisture Content ◽  
Nuclear Fuel ◽  
Dry Weight ◽  
Buffer Layers ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Buffer Material ◽  
Nuclear Fuel Waste

A full-scale nuclear fuel waste disposal container experiment was carried out 240 m below ground in an underground granitic rock research laboratory in Canada. An electric heater was surrounded by buffer material composed of sand and bentonite clay and provided heat equivalent to what is anticipated in a Canadian nuclear fuel waste repository. During the experiment, the heat caused a mass transport of water and moisture content gradients developed in the buffer ranging from 13% closest to the heater to 23% at the rock wall of the deposition hole. Upon decommissioning after 2.5 years, microorganisms could be cultured from all samples having a moisture content above 15% but not from samples with a moisture content below 15%. Heterotrophic aerobic and anaerobic bacteria were found in numbers ranging from 101to 106cells/g dry weight buffer. Approximately 102, or less, sulphate-reducing bacteria and methanogens per gram of dry weight buffer were also found. Identification of buffer population members was performed using Analytical Profile Index (API) strips for isolated bacteria and 16S rRNA gene sequencing for in situ samples. A total of 79 isolates from five buffer layers were identified with API strips as representing the beta, gamma and delta groups of Proteobacteria and Gram-positive bacteria. Sixty-seven 16S rRNA clones that were obtained from three buffer layers were classified into 21 clone groups representing alpha and gamma groups of Proteobacteria, Gram-positive bacteria, and a yeast. Approximately 20% of the population comprised Gram-positive bacteria. Members of the genera Amycolatopsis, Bacillus, and Nocardia predominated. Among Gram-negative bacteria, the genera Acinetobacter and Pseudomonas predominated. Analysis of lipid biomarker signatures and in situ leucine uptake demonstrated that the buffer population was viable. The results suggest that a nuclear fuel waste buffer will be populated by active microorganisms only if the moisture content is above a value where free water is available for active life.Key words: 16S rRNA, bacteria, bentonite, nuclear fuel waste, phospholipid fatty acids, water activity.

scholarly journals Cultivation-Independent Examination of Horizontal Transfer and Host Range of an IncP-1 Plasmid among Gram-Positive and Gram-Negative Bacteria Indigenous to the Barley Rhizosphere

2006 ◽  
Vol 72 (10) ◽  
pp. 6687-6692 ◽  
Author(s):  
Sanin Musovic ◽  
Gunnar Oregaard ◽  
Niels Kroer ◽  
Søren J. Sørensen
Keyword(s):  
16S Rrna ◽  
Host Range ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Gram Positive ◽  
Gram Negative ◽  
Indigenous Bacteria ◽  
Transfer Frequency

ABSTRACTThe host range and transfer frequency of an IncP-1 plasmid (pKJK10) among indigenous bacteria in the barley rhizosphere was investigated. A new flow cytometry-based cultivation-independent method for enumeration and sorting of transconjugants for subsequent 16S rRNA gene classification was used. Indigenous transconjugant rhizosphere bacteria were collected by fluorescence-activated cell sorting and identified by cloning and sequencing of 16S rRNA genes from the sorted cells. The host range of the pKJK10 plasmid was exceptionally broad, as it included not only bacteria belonging to the alpha, beta, and gamma subclasses of theProteobacteria, but alsoArthrobactersp., a gram-positive member of theActinobacteria. The transfer frequency (transconjugants per donor) from thePseudomonas putidadonor to the indigenous bacteria was 7.03 × 10−2± 3.84 × 10−2. This is the first direct documentation of conjugal transfer between gram-negative donor and gram-positive recipient bacteria in situ.

Lifetimes of Titanium and Copper Containers for the Disposal of Used Nuclear Fuel

1991 ◽  
Vol 257 ◽  
Author(s):  
Lawrence H. Johnson ◽  
D.W. Shoesmith ◽  
B.M. Ikeda ◽  
F. King
Keyword(s):  
Nuclear Fuel ◽  
Bulk Solution ◽  
General Corrosion ◽  
Compacted Clay ◽  
Used Nuclear Fuel ◽  
Buffer Material ◽  
Using Data ◽  
Long Term Performance ◽  
Term Performance ◽  
Nuclear Fuel Waste

ABSTRACTTitanium and copper have been proposed as suitable container materials for disposal of nuclear fuel waste in plutonic rock of the Canadian Shield. Studies of the corrosion of these materials have led to the development of container failure models to predict long-term performance. Crevice corrosion and hydrogen-induced cracking of titanium have been identified as potential failure mechanisms, and these two processes have been studied in detail. Using data from these studies as well as a number of conservative assumptions, titanium container lifetimes of 1200 to 7000 a have been estimated. For copper, general corrosion has been studied in detail in bulk solution and in compacted clay-based buffer material. Results indicate that the copper corrosion rate is likely to be controlled by the rate of transport of copper species away from the container surface. An assessment of copper pitting data suggests that pitting is an extremely improbable failure mechanism. The copper container failure model predicts minimum container lifetimes of 30 000 a. The results demonstrate that long lifetime containment can be provided, should performance assessment studies indicate the need for such an option.

The “Nostocoida limicola” story: resolving the phylogeny of this morphotype responsible for bulking in activated sludge

2002 ◽  
Vol 46 (1-2) ◽  
pp. 105-110 ◽  
Author(s):  
R.J. Seviour ◽  
J.-R. Liu ◽  
E.M. Seviour ◽  
C.A. McKenzie ◽  
L.L. Blackall ◽  
...  
Keyword(s):  
16S Rrna ◽  
Activated Sludge ◽  
Pure Culture ◽  
Sequence Analyses ◽  
Rrna Sequence ◽  
Gram Positive ◽  
16S Rrna Sequence ◽  
Culture Studies ◽  
Gram Positive Bacteria ◽  
Morphological Variants

On the basis of 16S rRNA sequence analyses of several isolates of “Nostocoida limicola” from activated sludge plants in Australia and other countries, it is clear that “N. limicola” I, II and III are not three morphological variants of a single bacterium but at least three phylogenetically different bacteria. Data show that “N. limicola” I are members of at least two genera in the low mol% G+C Gram-positive bacteria, while some isolates of “N.limicola” II belong to the high mol% G+C Gram positive bacteria, and “N.limicola” III is a member of the Planctomycetales. Design and application of 16S rRNA targeted probes for each to biomass samples suggests that their phylogeny is more diverse than pure culture studies would suggest.

scholarly journals 16S rRNA Sequences and Differences in Bacteria Isolated from the Muztag Ata Glacier at Increasing Depths

2005 ◽  
Vol 71 (8) ◽  
pp. 4619-4627 ◽  
Author(s):  
Shurong Xiang ◽  
Tandong Yao ◽  
Lizhe An ◽  
Bingliang Xu ◽  
Junxia Wang
Keyword(s):  
16S Rrna ◽  
Ice Core ◽  
Growth Conditions ◽  
Small Subunit ◽  
Bacterial Isolates ◽  
Gram Positive ◽  
Mountain Glacier ◽  
Gram Positive Bacteria ◽  
Rrna Sequences ◽  
16S Rrna Sequences

ABSTRACT Small subunit 16S rRNA sequences, growth temperatures, and phylogenetic relationships have been established for 129 bacterial isolates recovered under aerobic growth conditions from different regions of a 22-m ice core from the Muztag Ata Mountain glacier on the Pamirs Plateau (China). Only 11% were psychrophiles (grew at 2°C or −2°C up to ∼20°C), although the majority (82%) were psychrotolerant (grew at 2°C or −2°C up to 37°C). The majority of the isolates had 16S rRNA sequences similar to previously determined sequences, ranging from 85% to 100% identical to database sequences. Based on their 16S rRNA sequences, 42.6% of the isolates were high-G+C (HGC) gram-positive bacteria, 23.3% wereγ -Proteobacteria, 14.7% were α-Proteobacteria, 14.7% were Flavobacteria, and 4.7% were low-G+C (LGC) gram-positive bacteria. There were clear differences in the depth distribution, with Proteobacteria, HGC/Cytophaga-Flavobacterium-Bacteroides (CFB), Proteobacteria, LGC/CFB/HGC, Cryobacterium psychrophilum, HGC/CFB, Proteobacteria/HGC/CFB, and HGC/CFB being the predominant isolates from ice that originated from 2.7 to 3.8, 6.2, 7.5, 8.3, 9.0, 9.7, 12.5, and 15.3 m below the surface, respectively. This layered distribution of bacterial isolates presumably reflects both differences in bacteria inhabiting the glacier's surface, differences in bacteria deposited serendipitously on the glacier's surface by wind and snowfall, and nutrient availability within the ice.

Behavior of Listeria monocytogenes and Staphylococcus aureus in Yogurt Fermented with a Bacteriocin-Producing Thermophilic Starter

2002 ◽  
Vol 65 (5) ◽  
pp. 799-805 ◽  
Author(s):  
NOREDDINE BENKERROUM ◽  
HAFIDA OUBEL ◽  
LAMIAE BEN MIMOUN
Keyword(s):  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Lactobacillus Delbrueckii ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Bakery Yeast ◽  
Adsorption Desorption ◽  
And Staphylococcus Aureus

Streptococcus salivarius subsp. thermophilus B producing a bacteriocin active against Listeria monocytogenes ATCC 7644 and Staphylococcus aureus SAD 30 was isolated from bakery yeast. The bacteriocin was partially purified by an adsorption/desorption technique, and its spectrum of action was compared to that of a neutralized cell-free supernatant (CFS). Although the CFS inhibited a number of gram-positive and -negative bacteria of health and spoilage significance, the spectrum of action of the partially purified bacteriocin was limited to gram-positive bacteria. L. monocytogenes was the most sensitive to both preparations. The bacteriocin-producing streptococcal strain was used in combination with a Bac− Lactobacillus delbrueckii subsp. bulgaricus CY strain isolated from commercial yogurt to assess the effectiveness of the resulting thermophilic starter in controlling L. monocytogenes and S. aureus in yogurt during fermentation and storage at refrigeration (ca. 7°C) or abuse (ca. 22°C) temperature. Yogurt samples were contaminated with L. monocytogenes or S. aureus to the approximate levels of 103 and 106 CFU/ml of milk, respectively. The results showed that in situ bacteriocin production was more active against L. monocytogenes than against S. aureus in vitro and in contaminated samples. While L. monocytogenes leveled off below the detectable limit in a 1-ml sample of yogurt within 24 h of processing, S. aureus survived in Bac+ and Bac− samples during 10 days of storage at room temperature (ca. 22°C). Use of a Bac+ starter resulted in a 5-day extension of the shelf life.

Creep behaviour of a buffer material for nuclear fuel waste vault

1985 ◽  
Vol 22 (4) ◽  
pp. 541-550 ◽  
Author(s):  
Raymond N. Yong ◽  
Prapote Boonsinsuk ◽  
Demos Yiotis
Keyword(s):  
Finite Element ◽  
Nuclear Fuel ◽  
Host Rock ◽  
Creep Behaviour ◽  
Creep Model ◽  
Secondary Creep ◽  
Full Size ◽  
Waste Container ◽  
Buffer Material ◽  
Nuclear Fuel Waste

In the Canadian nuclear fuel waste disposal concept currently under study, one of the prime candidate procedures is the borehole emplacement technique. Each fuel waste container will be placed in a 1.1 m diameter hole in the floor of a disposal vault in deep plutonic rock. The container will be surrounded by buffer material consisting of a mixture of clay and sand. This study examines the creep behaviour of the buffer material in the borehole during interaction with the waste container and the host rock. It simulated the buffer – container – host rock interaction through a small-scale physical model using the loading pressures anticipated in the full-size system. The results from the model tests were compared with those predicted by a finite element analytical model. The creep behaviour of the full-size system was then predicted using the analytical model.From the results, it is evident that the creep behaviour of the buffer material depends significantly on interaction within the container – buffer – host rock system, overburden pressure, and water uptake. At relatively low overburden pressures, the waste container might settle, causing a separation between the buffer material and the container top. However, this could be alleviated by the swelling properties of the buffer material. The secondary creep rates are negligible, and creep in the buffer material is primarily governed by the primary creep stage. Key words: creep, model test, swelling soil, soil deformation, unsaturated soil, finite element analysis.

scholarly journals Influence of Vegetation on the In Situ Bacterial Community and Polycyclic Aromatic Hydrocarbon (PAH) Degraders in Aged PAH-Contaminated or Thermal-Desorption-Treated Soil

2009 ◽  
Vol 75 (19) ◽  
pp. 6322-6330 ◽  
Author(s):  
Aurélie Cébron ◽  
Thierry Beguiristain ◽  
Pierre Faure ◽  
Marie-Paule Norini ◽  
Jean-François Masfaraud ◽  
...  
Keyword(s):  
Bacterial Community ◽  
16S Rrna ◽  
Polycyclic Aromatic Hydrocarbon ◽  
16S Rrna Gene ◽  
Aromatic Hydrocarbon ◽  
Dry Weight ◽  
Rrna Gene ◽  
Degrading Bacteria ◽  
Polycyclic Aromatic

ABSTRACT The polycyclic aromatic hydrocarbon (PAH) contamination, bacterial community, and PAH-degrading bacteria were monitored in aged PAH-contaminated soil (Neuves-Maisons [NM] soil; with a mean of 1,915 mg of 16 PAHs·kg−1 of soil dry weight) and in the same soil previously treated by thermal desorption (TD soil; with a mean of 106 mg of 16 PAHs·kg−1 of soil dry weight). This study was conducted in situ for 2 years using experimental plots of the two soils. NM soil was colonized by spontaneous vegetation (NM-SV), planted with Medicago sativa (NM-Ms), or left as bare soil (NM-BS), and the TD soil was planted with Medicago sativa (TD-Ms). The bacterial community density, structure, and diversity were estimated by real-time PCR quantification of the 16S rRNA gene copy number, temporal thermal gradient gel electrophoresis fingerprinting, and band sequencing, respectively. The density of the bacterial community increased the first year during stabilization of the system and stayed constant in the NM soil, while it continued to increase in the TD soil during the second year. The bacterial community structure diverged among all the plot types after 2 years on site. In the NM-BS plots, the bacterial community was represented mainly by Betaproteobacteria and G ammaproteobacteria. The presence of vegetation (NM-SV and NM-Ms) in the NM soil favored the development of a wider range of bacterial phyla (Alphaproteobacteria, Betaproteobacteria, G ammaproteobacteria, Verrucomicrobia, Actinobacteria, Firmicutes, and Chlorof l exi) that, for the most part, were not closely related to known bacterial representatives. Moreover, under the influence of the same plant, the bacterial community that developed in the TD-Ms was represented by different bacterial species (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria) than that in the NM-Ms. During the 2 years of monitoring, the PAH concentration did not evolve significantly. The abundance of gram-negative (GN) and gram-positive (GP) PAH-degrading bacteria was estimated by real-time PCR quantification of specific functional genes encoding the α subunit of PAH-ring hydroxylating dioxygenase (PAH-RHDα). The percentage of the PAH-RHDα GN bacterial genes relative to 16S rRNA gene density decreased with time in all the plots. The GP PAH-RHDα bacterial gene proportion decreased in the NM-BS plots but stayed constant or increased under vegetation influence (NM-SV, NM-Ms, and TD-Ms).

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