Bacterial anaerobic respiration using selenium oxyanions as the sole electron acceptor primarily result in the precipitation of selenium biominerals observed as either intracellular or extracellular selenium deposits. Although a better understanding of the enzymology of bacterial selenate reduction is emerging, the processes by which the selenium nanospheres are constructed, and in some cases secreted, has remained poorly studied. Thauera selenatis is a Gram-negative betaproteobacterium that is capable of respiring selenate due to the presence of a periplasmic selenate reductase (SerABC). SerABC is a molybdoenzyme that catalyses the reduction of selenate to selenite by accepting electrons from the Q-pool via a dihaem c-type cytochrome (cytc4). The product selenite is presumed to be reduced in the cytoplasm, forming intracellular selenium nanospheres that are ultimately secreted into the surrounding medium. The secretion of the selenium nanospheres is accompanied by the export of a ~95 kDa protein SefA (selenium factor A). SefA has no cleavable signal peptide, suggesting that it is also exported directly for the cytoplasmic compartment. It has been suggested that SefA functions to stabilize the formation of the selenium nanospheres before secretion, possibly providing reaction sites for selenium nanosphere creation or providing a shell to prevent subsequent selenium aggregation. The present paper draws on our current knowledge of selenate respiration and selenium biomineralization in T. selenatis and other analogous systems, and extends the application of nanoparticle tracking analysis to determine the size distribution profile of the selenium nanospheres secreted.
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December 2012
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Conference Article|
November 21 2012
Biomineralization of selenium by the selenate-respiring bacterium Thauera selenatis
Clive S. Butler
;
Clive S. Butler
1
*Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K.
1To whom correspondence should be addressed (emailc.s.butler@exeter.ac.uk).
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Charles M. Debieux
;
Charles M. Debieux
*Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K.
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Elizabeth J. Dridge
;
Elizabeth J. Dridge
*Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K.
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Peter Splatt
;
Peter Splatt
*Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K.
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Matthew Wright
Matthew Wright
†NanoSight Ltd, Minton Park, London Road, Amesbury SP4 7RT, U.K.
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Biochem Soc Trans (2012) 40 (6): 1239–1243.
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Received:
March 26 2012
Citation
Clive S. Butler, Charles M. Debieux, Elizabeth J. Dridge, Peter Splatt, Matthew Wright; Biomineralization of selenium by the selenate-respiring bacterium Thauera selenatis. Biochem Soc Trans 1 December 2012; 40 (6): 1239–1243. doi: https://doi.org/10.1042/BST20120087
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