Effect of Vitreoscilla hemoglobin gene (vgb) and metabolic inhibitors on cadmium uptake by the heterologous host Enterobacter aerogenes

The effect of metabolic inhibitor/uncoupler(s) (CCCP and NaN3) and sulfhydryl reagents (dithiothreitol, 2-mercaptoethanol glutathione) on cadmium uptake was investigated in Enterobacter aerogenes strains. They include a transformed strain bearing the Vitreoscilla hemoglobin gene, vgb as well as control strains that lack this transformed gene. The vgb-harboring strains showed better uptake of cadmium than vgb-lacking strains. Under low aeration, there was 2-fold enhancement of Cd+2 uptake in vgb-harboring strains compared with 1.6-fold enhancement under high aeration. The CCCP caused 36, 40 and 58% inhibition in cadmium uptake of parental, pUC9-harboring and VHb-expressing cells, respectively. Similarly, the sodium azide exerted 44, 38 and 55% inhibition in Cd+2 uptake of parental, pUC9-harboring and VHb-expressing cells, respectively. Less extensive inhibition of Cd+2 uptake in the range of 11–39% was observed with sulfhydryl reagents.