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

Abstract

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.

Identification of algal rich microbial blooms in the Sellafield Pile Fuel Storage Pond and the application of ultrasonic treatment to control the formation of blooms

“…Efforts to determine the microbial community in biofilms could provide useful information about whether there are other organisms that might be useful for bioremediation of radionuclide-containing waters and other applications, as well as add to current understanding of biofouling problems in inhospitable nuclear environments. A range of other indoor SNFPs have been studied more recently ( Rivasseau et al, 2013 ; Tišáková et al, 2013 ; Karley et al, 2017 ; Bagwell et al, 2018 ; Ruiz-Lopez et al, 2020 ), and in some cases have been shown to host stable microbial communities over extended periods of time, as was observed in an indoor SNFP on the Sellafield site that was dominated by the hydrogen-metabolising genus Hydrogenophaga ( Ruiz-Lopez et al, 2020 ).…”

Study on Degradation of 1,2,4-TrCB by Sugarcane Cellulose-TiO2 Carrier in an Intimate Coupling of Photocatalysis and Biodegradation System

“…Hence, it plays an important role in water purification and the carbon cycle. Moreover, the Sediminibacterium genus was found to be one of the dominant bacteria in the storage pool of radioactive materials [ 52 ], and the reclaimed water was treated with a low concentration of chlorine [ 53 ], signifying its oxidation resistance. However, the dominant bacteria were replaced by the Acidovorax genus when the reclaimed water was treated with ultraviolet and chlorine together [ 54 ], indicating that ultraviolet light had adverse effects on the Sediminibacterium genus.…”

Taxonomical composition and functional analysis of biofilms sampled from a nuclear storage pool

“…The Caulobacter strain OR37 isolated from subsurface sediments at Oak Ridge (USA) was proven to be tolerant to 200 μM of uranium at pH 7 ( Utturkar et al, 2013 ). The genus Caulobacter has been identified in spent nuclear fuel storage pools in Sellafield (UK) ( Foster et al, 2020 ; Ruiz-Lopez et al, 2020 ). Caulobacter bacteria are well known for their distinctive ability to live in low-nutrient environments ( Hu et al, 2005 ).…”