Development of an ultra-sensitive biosensor for the detection of gold
Harpreet Bhatia1,2, John B. Bruning1, Peter Hoffmann1 and Frank Reith1,2
1School of Biological Sciences, The University of Adelaide, SA 5005, Australia
2CSIRO Land and Water, Environmental Biogeochemistry, PMB2, Glen Osmond,
South Australia 5064, Australia
Biofilms living on gold (Au) grains contribute to dissolution, precipitation and aggregation of Au leading to the formation, growth and dispersion of Au nanoparticles (Au-NPs) and secondary biomorphic Au. Bacterial biofilms associated with Au grains have been found at >15 sites in Australia. On grains from many sites the metallophilic β-proteobacterium Cupriavidus metallidurans CH34 is able to counteract the toxic effects of cytoplasmic Au(III)-complexes by sequestering Au-species. During detoxification, the Au(III)-complexes are reduced and periplasmic Au-NPs are formed. The Au-NPs are released into the surface environment upon disintegration of the biofilms, thereby enhancing environmental mobility of Au. One of the proteins involved in detoxification was identified as the copper chaperone protein (CupC). It has been postulated that the identification of CupC can open ways for the potential development of bioexploration for in-field detection of Au. The aim of the present study was to isolate and purify CupC in Escherichia.coli. The gene for CupC (15 kDa) was amplified and Gateway cloned into pDEST57. NusA (55 kDa) along with a His6 affinity tag was used for efficient production of stable and soluble fusion protein containing CupC. The fusion protein (CupC-Nus) was over-expressed and purified and its expression was confirmed by gel electrophoresis. Future experiments will include further purification and crystallization trials of CupC and identification of a reagent compatible with CupC for the selective extraction of Au from environmental samples. Purification of CupC may lead to the development of a protein-based biosensor to detect Au which can improve the efficiency of its exploration.