Engineering Deinococcus radiodurans for metal remediation in radioactive mixed waste environments

We have developed a radiation resistant bacterium for the treatment of mixe d radioactive wastes containing ionic mercury. The high cost of remediating radioactive waste sites from nuclear weapons production has stimulated the development of bioremediation strategies using Deinococcos radiodurans, th e most radiation resistant organism known. As a frequent constituent of the se sites is the highly toxic ionic mercury (Hg) (II), we have generated sev eral D. radiodurans strains expressing the cloned Hg (II) resistance gene ( merA) from Escherichia coli strain BL308. We designed four different expres sion vectors for this purpose, and compared the relative advantages of each , The strains were shown to grow in the presence of both radiation and ioni c mercury at concentrations well above those found in radioactive waste sit es, and to effectively reduce Hg (II) to the less toxic volatile elemental mercury. We also demonstrated that different gene clusters could be used to engineer D. radiodurans for treatment of mixed radioactive wastes by devel oping a strain to detoxify both mercury and toluene. These expression syste ms could provide models to guide future D. radiodurans engineering efforts aimed at integrating several remediation functions into a single host.