Uranium and neptunium retention mechanisms in Gallionella ferruginea/ferrihydrite systems for remediation purposes.

The ubiquitous β-Proteobacterium Gallionella ferruginea is known as stalk-forming, microaerophilic iron(II) oxidizer, which rapidly produces iron oxyhydroxide precipitates. Uranium and neptunium sorption on the resulting intermixes of G. ferruginea cells, stalks, extracellular exudates, and precipitated iron oxyhydroxides (BIOS) was compared to sorption to abiotically formed iron oxides and oxyhydroxides.

Culture-dependent comparison of microbial diversity in deep granitic groundwater from two sites considered for a Swedish final repository of spent nuclear fuel.

Site selection for a spent nuclear fuel (SNF) repository required analysis of microbial abundance and diversity at two Swedish sites, Forsmark and Laxemar-Simpevarp. Information about sulphate-reducing bacteria (SRB) was required, as sulphide could corrode copper SNF canisters. Total number of cells (TNC) and ATP were analysed, and plate counts and most probable number (MPN) analyses were conducted using eight media based on different electron donors and acceptors for specific microorganism physiological groups.

Numbers, biomass and cultivable diversity of microbial populations relate to depth and borehole-specific conditions in groundwater from depths of 4-450 m in Olkiluoto, Finland.

Microbiology, chemistry and dissolved gas in groundwater from Olkiluoto, Finland, were analysed over 3 years; samples came from 16 shallow observation tubes and boreholes from depths of 3.9-16.2 m and 14 deep boreholes from depths of 35-742 m.

Propylphenols are metabolites in the anaerobic biodegradation of propylbenzene under iron-reducing conditions.

The metabolism of monoaromatic hydrocarbons by an iron-reducing bacterial enrichment culture originating from diesel-contaminated groundwater was examined using d7-propylbenzene as a model hydrocarbon. Sequence analysis of the 16S rDNA gene showed that the dominant part (10 of 10 clones) of the enrichment culture consisted of a bacterium closely related to clones found in benzene-contaminated groundwater and to the iron-reducing beta-proteobacterium, Rhodoferax ferrireducens (similarity values were 99.5% and 98.

Distribution, diversity and activity of microorganisms in the hyper-alkaline spring waters of Maqarin in Jordan.

The hyper-alkaline, high-Ca(2+) springs of Maqarin, Jordan, were investigated as an analogue for various microbial processes at the extremely high pH generated by cement and concrete in some underground radioactive waste repositories. Leaching of metamorphic, cementitious phases in Maqarin has produced current, hyper-alkaline groundwater with a maximum pH of 12.9.

Determination and distribution of diesel components in igneous rock surrounding underground diesel storage facilities in Sweden.

In Sweden, a preliminary investigation of the contamination situation of igneous rock surrounding underground storage facilities of diesel showed that the situation was severe. The diesel was believed to have penetrated into the rock as far as 50 m from the walls of the vaults. Consequently, the risk for contamination of groundwater and recipients could not be neglected.

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

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.

Diversity and distribution of subterranean bacteria in groundwater at Oklo in Gabon, Africa, as determined by 16S rRNA gene sequencing.

This paper describes how ground water was sampled, DNA extracted, amplified and cloned and how information available in the ribosomal 16S rRNA gene was used for mapping diversity and distribution of subterranean bacteria in groundwater at the Bangombé site in the Oklo region. The results showed that this site was inhabited by a diversified population of bacteria. Each borehole was dominated by species that did not dominate in any of the other boreholes; a result that probably reflects documented differences in the geochemical environment.

Benefits associated with the stalk of Gallionella ferruginea, evaluated by comparison of a stalk-forming and a non-stalk-forming strain and biofilm studies in situ.

Factors that regulate and induce stalk formation by the iron-oxidizing and stalk-forming bacterium Gallionella ferruginea were studied in laboratory cultures and in situ. A stalk-forming strain, Sta(+), and a non-stalk-forming strain, Sta(-), were used for comparative studies of the benefits associated with the stalk. Two different growth media were used: a ferrous sulfide medium (FS-medium), with slow oxidation of iron giving high concentrations of toxic oxygen radicals and a ferrous carbonate medium (FC-medium), with fast iron oxidation giving low concentration of the toxic oxygen radicals.

Phylogeny and phenotypic characterization of the stalk-forming and iron-oxidizing bacterium Gallionella ferruginea.

The 16S rRNA gene of Gallionella ferruginea was amplified by polymerase chain reaction and sequenced by direct double-stranded sequencing. The phylogenetic analysis placed G. ferruginea in the beta-group of the Proteobacteria, with 90.