1.8.5.5 environmental protection Escherichia coli expressing thiosulfate reductase genes (phsABC) from Salmonella typhimurium is able to remove significant amounts of heavy metals from the medium within 24 h: 99% of zinc up to 500 microM, 99% of lead up to 200 microM, 99% of 100 icroM and 91% of 200 icroM cadmium. In a mixture of 100 microM each of cadmium, lead, and zinc, the strain removes 99% of the total metals from solution within 10 h. Cadmium is removed first, lead second, and zinc last 645578 1.8.5.5 environmental protection Escherichia coli strains harboring thiosulfate reductase gene phsABC expression constructs show higher thiosulfate reductase activity and produce significantly more sulfide than the control strains under both aerobic and anaerobic conditions. The most effecitve expression construct produces thiosulfate reductase at the highest level and removes the most cadmium from solution under anaerobic conditions: 98% of all concentrations up to 150 microM and 91% of 200 microM. The metal removed from solution precipitates as a complex of cadmium and sulfur, most likely cadmium sulfide -, 737488