Resumo

Mercury bioremediation by Cupriavidus metallidurans strain MSR33 generated for mercury removal Luis A. Rojas, Myriam González and Michael Seeger Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química and Center of Nanotechnology and Systems Biology, Universidad Técnica Federico Santa María, Valparaíso, Chile. luisrojasaraya@gmail.com The heavy metal-resistant model bacterium Cupriavidus metallidurans strain CH34 harbors two large plasmids, pMOL28 and pMOL30, which carry genetic determinants for heavy metal resistance. Each plasmid contains a merRTPADE operon that confers a low and narrow-spectrum mercury resistance (0.05 mM Hg²⁺). To improve inorganic and to confer a novel organic mercury resistance, the IncP-1&beta plasmid pTP6 carrying a complex set of mer genes was introduced into strain CH34 by biparental mating. The novel strain MSR33 showed a 2.4 fold increase in the minimum inhibitory concentration to Hg²⁺ and acquired a novel resistance to CH3Hg⁺. The novel Cupriavidus metallidurans MSR33 was studied for mercury bioremediation in water, sludge and soil. The experiments were performed in microcosms containing Hg-polluted water or Hg-polluted soils at 30 ^°C in a water bath. In order to supply air to the system and agitation, the microcosms were aerated by a blower. Volatilized mercury was captured in an external trap containing 10% of HNO3. Residual mercury was measured in an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-OES). Resting cell experiments demonstrate that strain MSR33 was capable to remove 20 and 30 ppm of Hg²⁺ in polluted water after 2 h. C. metallidurans strain MSR33 removed Hg²⁺ together with CH3Hg⁺ from polluted sludge and more than 75% of a mixture containing 25 ppm of Hg²⁺ and CH3Hg⁺ from a polluted soil. C. metallidurans MSR33 generated for mercury bioremediation could be useful for mercury removal from polluted water, sludge and soil in presence of other heavy metals. Acknowledgements: MECESUP FSM0710 postdoctoral fellowship (LAR) and USM (131109, 130948 and 130836), CN&BS and FONDECYT 1110992 grants.