Expression of hutZEp is regulated by Fur. A RT-qPCR was performed with total RNA extracted from wild-type TX01 and a fur mutant strain cultured in normal LB medium. The expression level of hutZEp in the wild-type TX01 strain was set at 1. B DH5α/pSZ283/pTFur and DH5α/pSZ283/pT were streaked and cultured on LB plates with X-gal, kanamycin, and ampicillin. C The expression of HutZ was examined by Western blot. 1. the expression of HutZ in wild type TX01; 2. the expression of HutZ in fur mutant strain. D Interaction between Fur and the speculative promoter regions of hutZEp. An electrophoresis mobility shift assay (EMSA) was performed in binding buffer containing Fur, unlabelled or carboxyfluorescein-labelled negative control DNA (NCD), and carboxyfluorescein-labelled D333. The negative control DNA (NCD) was derived from a fragment of the pT plasmid. Data are presented as the means ± SEMs (N = 3). N, the number of times the experiment was performed. **P < 0.01.