Effects of exogenous sulfate on the chromium(VI) metabolism of chromium(VI)-resistant engineered strains.

Objective: To explore the effects of exogenous sulfate on the efficiency of chromium(VI) metabolism of three chromium(VI)-resistant Escherichia coli strains (eChrA / eChrB / eChrAB) by adding chromium(VI)-resistance genes chrA and/or chrB, for better understanding and further application of these Cr(VI)-resistant strains in environmental and industrial chromium removal.

Methods: Based on three engineered Cr(VI)-resistant strains exposed to different concentrations of sulfate: i) Evaluation of Cr(VI) metabolism characteristics, including the growth rate, the Cr(VI) tolerance, the removal, absorption and efflux capacity of Cr(VI); ii) Detection the expressions of Cr(VI) resistance-related genes (chrA and chrB), and sulfate channel protein-related genes (sbp, cysA, cysU and cysW genes) by RT-qPCR.

Results: Exogenous sulfate enhanced the Cr(VI) tolerance and the removal rate of these three engineered Cr(VI)-resistant strains, and promoted their growth rate under Cr(VI) stress, while suppressed their absorption and efflux capacity.

Chromium metabolism characteristics of coexpression of ChrA and ChrT gene.

Objective: Serratia sp. S2 is a wild strain with chromium resistance and reduction ability. Chromium(VI) metabolic-protein-coding gene ChrA and ChrT were cloned from Serratia sp.

Chromium resistance characteristics of Cr(VI) resistance genes ChrA and ChrB in Serratia sp. S2.

Objective: To find an efficient chromium (VI) resistance system, with a highly efficient, economical, safe, and environmentally friendly chromium-removing strain, ChrA, ChrB, and ChrAB fragments of the chromium (VI) resistance gene in Serratia sp. S2 were cloned, and their prokaryotic expression vectors were constructed and transformed into E. coli BL21.