Isolation and characterization of indigenous copper-resistant actinomycete strains

Abstract

Fifty actinomycetes were isolated from copper contaminated and non-contaminated area. Primary qualitative screening assays showed that 100% of the isolated microorganisms of the contaminated area were resistant up to 80 mg L 1 of CuSO4. On the other hand, 100% of isolates from non-contaminated area grew at 16 mg L 1, 87.4% at 40 mg L 1 and only 19.4% of them were capable of growing at 80 mg L 1 of CuSO4. The semiquantitative assay showed that the isolated strains from the sediments of the contaminated site were resistant up to the highest concentration tested (1000 mg L 1) with the exception of AB2C strain; however, the strains isolated from non-contaminated sediments were sensitive to Cu2+ concentrations higher than 200 and 400 mg L 1, respectively. Microbial growth of AB0 strain in presence of 39 mg L 1 copper showed an inhibition of 32% after 6 days of incubation as compared to the control, and copper residual concentration indicated a reduction in the supernatant of 71.2% after 6 days of incubation: pellet acid digestion proved that copper was accumulated by the cells. 16S rDNA restriction digestion of 1300 bp amplicons with CfoI and HpaII showed only.