Cd and Zn contents of E. coli expressing BjHMA4R. E. coli BL21 cells transformed with a pEASY-Blunt E1 expression plasmid or a pEASY-Blunt E1 expression plasmid that harbored BjHMA4R were grown in normal liquid LB medium overnight, then supplemented with 50 μM CdCl2 (b), 100 μM CdCl2 (c), 200 μM ZnCl2 (e) and normal LB (a, d). The cells were incubated at 37 °C for 10 h and 20 h. The metal contents of the samples were analyzed with inductively coupled plasma-mass spectrometry (ICP-MS). The results are the means ± SEs of four independent experiments performed with four different colonies. Different letters above the columns indicate significant differences (P < 0.05) between cell groups under the same stress treatment.