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. Author manuscript; available in PMC: 2018 Nov 1.

Published in final edited form as: Mol Microbiol. 2017 Sep 13;106(3):469–478. doi: 10.1111/mmi.13826

Fig. 4 — Expression of the gfp reporter gene was assayed as described under Experimental Procedures. A) Mutagenesis of Cys83, Cys101 and Cys102 and their contribution to MAs(III) binding. Cells were grown in M9 medium for 14 h. Cells of E. coli strain AW3110(DE3) bearing plasmids with wild type SpArsR, C83S, C101S or the C102S mutant in trans with reporter plasmid pACYC184-ParsP-gfp were grown without arabinose (solid black bars ((left)), 0.2% arabinose (open bars (middle)), or 0.2% arabinose and 2 μM MAs(III) (solid grey bars (right)). B) Comparison of the response of the bacterial biosensor to inorganic and organic arsenicals. Additions: (●), As(III); (▼), As(V); (△), MAs(III); (■), MAs(V).

C) SpArsR can be converted to an As(III)-responsive ArsR by introduction of an additional cysteine residue from AfArsR. SpArsR with addition of the C-terminus of AfArsR containing AfArsR Cys102 (SpArsR_AC) responds to As(III) four-fold better than the wild type. As(III) and MAs(III) were assayed at the indicated concentrations. Fluorescence intensities of cell suspensions were quantified using a Photon Technology International spectrofluorometer with an excitation wavelength of 470 nm and emission wavelength of 510 nm. The data are the mean ± SE (n = 3).

Fig. 4 — Expression of the gfp reporter gene was assayed as described under Experimental Procedures. A) Mutagenesis of Cys83, Cys101 and Cys102 and their contribution to MAs(III) binding. Cells were grown in M9 medium for 14 h. Cells of E. coli strain AW3110(DE3) bearing plasmids with wild type SpArsR, C83S, C101S or the C102S mutant in trans with reporter plasmid pACYC184-ParsP-gfp were grown without arabinose (solid black bars ((left)), 0.2% arabinose (open bars (middle)), or 0.2% arabinose and 2 μM MAs(III) (solid grey bars (right)). B) Comparison of the response of the bacterial biosensor to inorganic and organic arsenicals. Additions: (●), As(III); (▼), As(V); (△), MAs(III); (■), MAs(V).

C) SpArsR can be converted to an As(III)-responsive ArsR by introduction of an additional cysteine residue from AfArsR. SpArsR with addition of the C-terminus of AfArsR containing AfArsR Cys102 (SpArsR_AC) responds to As(III) four-fold better than the wild type. As(III) and MAs(III) were assayed at the indicated concentrations. Fluorescence intensities of cell suspensions were quantified using a Photon Technology International spectrofluorometer with an excitation wavelength of 470 nm and emission wavelength of 510 nm. The data are the mean ± SE (n = 3).