Screening And Characterization Of Heavy Metal-Resistant Actinomycetes Isolated From A Lead Zinc Ore Tailings

Two hundred and two lead-resistant and one hundred and eight zinc-resistant actinomycetes were isolated from a sample of lead zinc contaminated soil collected from a lead zinc ore tailings in Huixian, Gansu Province, northwest of China by the dilution plating method. Two of the isolate were re-isolated to the further heavy metal-resistant studies. One of the isolate was found to be strongly resistant to the heavy metal lead, designated CCNWHX13-160T. Another one was strongly resistant to the heavy metal zinc, designated CCNWHX72-14.The heavy metal-resistant study result showed that the MIC (minimum inhibitory concentrations) of Pb2+ for growth of strain CCNWHX13-160T was 4.0 mM and the MIC (minimum inhibitory concentrations) of Zn2+ for growth of strain CCNWHX72-14 was 11.42 mM. Furthermore, strain CCNWHX13-160T has an ability of the absorption 94.46 % of Pb2+ from the liquid medium which was supplemented with 1mM Pb2+. Strain CCNWHX72-14 was able to absorb 87.22 % of Zn2+ from the liquid medium with 2mM Zn2+. There was potential capacity of actinomycetes as tools for Pb2+ and Zn2+ contamination bioremediation.The taxonomic position of strain CCNWHX13-160T was determined by using a polyphasic approach. The isolate had chemical and morphological properties of streptomycetes. The whole cell hydrolysates chemotaxonomic tests of the isolate showed that the LL-diaminopimelic acid (LL-DAP), arabinose, galactose, but no diagnostic sugars were contained. It was the cell-wall type I. The major menaquinones of the strain were hexahydrogenated, octahydrogenated and tetrahydrogenated with nine isoprene units [MK-9 (H6, H8 and H4)]. The major polar lipids were isoprenologues, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. It was phospholipid type II. The major fatty acid components analysis showed that the organism mainly contained iso- and anteiso- branched-chain and a proportion of unsaturated fatty acids. An almost complete 16S rRNA gene sequence analysis assigned strain CCNWHX13-160T to the genus Streptomyces and a distinct phyletic line was formed with validly published Streptomyces species. The strain was most similar to the type strains of Streptomyces pseudovenezuelae NBRC 12904 (98.9 %) and Streptomyces resistomycificus NBRC 12814 (98.8 %). Furthermore, DNA–DNA hybridization with these two Streptomyces species showed 49.7 %and 43.2 % relatedness, respectively. It is proposed that CCNWHX13-160T (=ACCC 41207T = HAMBI 2991T) be classified as the type strain of a novel species in the genus Streptomyces, Streptomyces resistoplumbeus sp. nov.