isolation of extremely heavy metal resistant strains of rare actinomycetes fromhighmetalcontent soils in iran

using of microorganisms to remove industrial pollutions of environment is an efficient methodthat mimics natural process and decrease remediation cost. in this study, 450 actinomycete strains wereisolated from high metal content soils in iran. heavy metal salt solutions in different concentrations were usedto isolate the resistant strains. 40 resistant actinomycetes which they showed highly resistance to the mostapplied heavy metals were selected. after examination of these strains in broth media with high levels ofmetals, 13 resistant isolates were selected as high resistant actinomycetes. some strains showed resistance to140 mm zncl2, 7 mm cuso4, 9.2 mm cdcl2, and 60 mm nicl2. molecular identification revealed thatresistant strains belonged to different actinomycetes genera including streptomyces,nonomuraea, saccharothrix,streptosporangium and promicromonospora which was the first report on occurrence of highly metal resistantstrains in nonomuraea, streptosporangium and promicromonospora genera. cadmium removal studies bypromicromonospora sp. utmc 2243 indicated 96.5% reduction in cadmium residual concentration, reflectingcadmium removal capacity in promicromonospora sp. utmc 2243.