Isolation of Extremely Heavy Metal Resistant Strains of Rare Actinomycetes fromHighMetalContent Soils in Iran

Document Type : Original Research Paper



Using of microorganisms to remove industrial pollutions of environment is an efficient method
that mimics natural process and decrease remediation cost. In this study, 450 actinomycete strains were
isolated from high metal content soils in Iran. Heavy metal salt solutions in different concentrations were used
to isolate the resistant strains. 40 resistant actinomycetes which they showed highly resistance to the most
applied heavy metals were selected. After examination of these strains in broth media with high levels of
metals, 13 resistant isolates were selected as high resistant actinomycetes. Some strains showed resistance to
140 mM ZnCl2, 7 mM CuSO4, 9.2 mM CdCl2, and 60 mM NiCl2. Molecular identification revealed that
resistant strains belonged to different actinomycetes genera including Streptomyces,Nonomuraea, Saccharothrix,
Streptosporangium and Promicromonospora which was the first report on occurrence of highly metal resistant
strains in Nonomuraea, Streptosporangium and Promicromonospora genera. Cadmium removal studies by
Promicromonospora sp. UTMC 2243 indicated 96.5% reduction in cadmium residual concentration, reflecting
cadmium removal capacity in Promicromonospora sp. UTMC 2243.