Limits...
Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions.

Newsome L, Morris K, Lloyd JR - PLoS ONE (2015)

Bottom Line: Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK.Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite.Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, United Kingdom.

ABSTRACT
Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions.

No MeSH data available.


Related in: MedlinePlus

Uranium-phosphate biomineralisation experiment: TEM images (a, b, c), k3 weighted EXAFS data (d), non-phase shift corrected Fourier transform of EXAFS data (e) and XRD spectra (f).Dashed lines in XAS spectra represent the best fit of the data. * are peaks from uranyl phosphates (S6 Fig shows the peak pattern). Experiments were conducted in an anaerobic freshwater minimal medium with glycerol phosphate as the electron donor and both fumarate and U(VI) as electron acceptors. Results confirmed the precipitate to be a uranyl phosphate biomineral of the autunite group.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4488441&req=5

pone.0132392.g002: Uranium-phosphate biomineralisation experiment: TEM images (a, b, c), k3 weighted EXAFS data (d), non-phase shift corrected Fourier transform of EXAFS data (e) and XRD spectra (f).Dashed lines in XAS spectra represent the best fit of the data. * are peaks from uranyl phosphates (S6 Fig shows the peak pattern). Experiments were conducted in an anaerobic freshwater minimal medium with glycerol phosphate as the electron donor and both fumarate and U(VI) as electron acceptors. Results confirmed the precipitate to be a uranyl phosphate biomineral of the autunite group.

Mentions: The Serratia species was incubated in anaerobic freshwater minimal medium with 10 mM glycerol phosphate, 1 mM U(VI) and 20 mM fumarate, to assess whether it could facilitate the precipitation of uranyl phosphate biominerals under these conditions. After a lag phase of approximately 50 hours, the optical density began to increase, and U(VI) was removed from solution (Fig 1A). The rates of U(VI) removal observed were broadly comparable with other studies [29,30], although differences in biogeochemical conditions preclude a direct comparison. Phosphate was released to solution concurrently (S2 Fig). A cream coloured precipitate formed which was identified as containing autunite group uranyl phosphates (Fig 2). TEM images showed cells coated in dense agglomerations of sheets of mineral, sometimes folded up into rolls (Fig 2). The lack of clearly defined peaks in the SAED spectrum suggested that the mineral phases were amorphous, and this was supported by high resolution images showing the mineral to be unstructured at the nanoscale. The discrepancy between the well-defined XRD peaks and the amorphous SAED pattern may be due to the autunite rapidly dehydrating in air to meta-autunite [31] during the TEM analysis, despite the maintenance of anaerobic conditions during sample drying and transport.


Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions.

Newsome L, Morris K, Lloyd JR - PLoS ONE (2015)

Uranium-phosphate biomineralisation experiment: TEM images (a, b, c), k3 weighted EXAFS data (d), non-phase shift corrected Fourier transform of EXAFS data (e) and XRD spectra (f).Dashed lines in XAS spectra represent the best fit of the data. * are peaks from uranyl phosphates (S6 Fig shows the peak pattern). Experiments were conducted in an anaerobic freshwater minimal medium with glycerol phosphate as the electron donor and both fumarate and U(VI) as electron acceptors. Results confirmed the precipitate to be a uranyl phosphate biomineral of the autunite group.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488441&req=5

pone.0132392.g002: Uranium-phosphate biomineralisation experiment: TEM images (a, b, c), k3 weighted EXAFS data (d), non-phase shift corrected Fourier transform of EXAFS data (e) and XRD spectra (f).Dashed lines in XAS spectra represent the best fit of the data. * are peaks from uranyl phosphates (S6 Fig shows the peak pattern). Experiments were conducted in an anaerobic freshwater minimal medium with glycerol phosphate as the electron donor and both fumarate and U(VI) as electron acceptors. Results confirmed the precipitate to be a uranyl phosphate biomineral of the autunite group.
Mentions: The Serratia species was incubated in anaerobic freshwater minimal medium with 10 mM glycerol phosphate, 1 mM U(VI) and 20 mM fumarate, to assess whether it could facilitate the precipitation of uranyl phosphate biominerals under these conditions. After a lag phase of approximately 50 hours, the optical density began to increase, and U(VI) was removed from solution (Fig 1A). The rates of U(VI) removal observed were broadly comparable with other studies [29,30], although differences in biogeochemical conditions preclude a direct comparison. Phosphate was released to solution concurrently (S2 Fig). A cream coloured precipitate formed which was identified as containing autunite group uranyl phosphates (Fig 2). TEM images showed cells coated in dense agglomerations of sheets of mineral, sometimes folded up into rolls (Fig 2). The lack of clearly defined peaks in the SAED spectrum suggested that the mineral phases were amorphous, and this was supported by high resolution images showing the mineral to be unstructured at the nanoscale. The discrepancy between the well-defined XRD peaks and the amorphous SAED pattern may be due to the autunite rapidly dehydrating in air to meta-autunite [31] during the TEM analysis, despite the maintenance of anaerobic conditions during sample drying and transport.

Bottom Line: Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK.Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite.Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, United Kingdom.

ABSTRACT
Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions.

No MeSH data available.


Related in: MedlinePlus