Nickel and Cobalt Removal Capacities of Native Metal-Resistant Bacteria

Genetic determinants for heavy metal resistance could be exploited in the design of bioprocesses for environmental cleanup. The removal of Ni(II), Co(II), Cr(VI) and Mn(II) was investigated using Serratia marcescens strains C-1, C4, 16 and Kluyvera sp. Nic3 isolated from nickel deposits in Moa, Holguin (Cuba). The high nickel and cobalt resistance of S. marcescens C-1 is based on the NreB- genetic determinant ncrABC, which encodes histidine-rich proteins, NcrA, NcrB and NcrC. NcrC is a Ni(II)/Co(II) uptake protein. In this work the presence of ncrAB fragment in S. marcescens C4, 16 and Kluyvera sp. Nic3 was determined by PCR. ncrAB fragment was efficiently amplified from genomic DNA of the strains C4 and 16 but not from strain Nic3. Strains C4, 16 and C-1 showed the highest resistance to Ni(II) and Co(II). The Ni(II)/Co(II) removal capacities of C4, 16 and C-1 strains were two times higher than that by Nic3 (12.88 mg of Ni(II)/g of biomass and 9.77 mg of Co(II)/g of biomass). Uptake of Cr(VI) and Mn(II) was not observed for any of these strains. pH value has an important influence on the Ni(II) and Co(II) removal capacity of S. marcescens C-1. Additional studies are currently in progress aimed to check the metal removal efficiency of strain C1 in batch reactors.