Evidence for high affinity nickel transporter genes in heavy metal resistant Streptomyces spec.

We have isolated 25 new strains of streptomycetes from soil samples of a po lluted site at the former uranium mine, Wismut, in eastern Thuringia, Germa ny. The strains grew on medium containing 1 mM NiCl2 and thus were resistan t to the heavy metal ion. Seven of the strains were further characterized. All of these strains were resistant to heavy metals in various degrees with up to 10 mM resistance against NiCl2 supplied with the liquid minimal grow th medium. The high level of resistance prompted us to look for high affini ty nickel transporter genes thought to provide a means to eliminate the exc ess nickel ions form the cells. Degenerate oligonucleotide primers derived from sequences of P-type ATP ase transporter genes of Gram negative bacteri a identified a fragment which shows deduced amino acid sequence similaritie s to known high affinity nickel transporters. Investigation of two genes ob tained from the isolates Streptomyces spec. E8 and F4 showed high sequence divergence. This was unexpected since a transmissible plasmid had been thou ght to convey heavy metal resistance.