Cadmium, lead, and zinc removal by expression of the thiosulfate reductasegene from Salmonella typhimurium in Escherichia coli

The thiosulfate reductase gene (phsABC) from Salmonella typhimurium was exp ressed in Escherichia coli in order to produce sulfide from inorganic thios ulfate and precipitate metals as metal sulfide complexes. The sulfide-engin eered strain removed significant amounts of heavy metals from the medium wi thin 24 h: 99% of zinc up to 500 mu M, 99% of lead up to 200 mu M, 99% of 1 00 mu M and 91% of 200 mu M cadmium. In a mixture of 100 mu M each of cadmi um, lead, and zinc, the strain removed 99% of the total metals from solutio n within 10 h. Cadmium was removed first, lead second, and zinc last. These results have important implications for removal of metals from wastewater contaminated with several metals.