Screening of Soil for Lead-Tolerant Fungi

Soil samples were screened for fungi tolerant to lead (lead nitrate) using poisoned food technique. Control media as well as media supplemented with 40 ppm, 200 ppm and 400 ppm concentrations of lead (in the form of lead nitrate) were used to isolate fungi by serial dilution plate method. In total, 19 species of fungi were isolated. Out of these, six species, i.e. Aspergillus niger var. niger Tiegh, an unidentified sterile species, Sepedonium chrysospermum (Bull) Fr., Trichoderma lignorum var. lignorum (Tode) Harz, Penicillium implicatum var. implicatum Biourge and Aspergillus candidus var. candidus Link could tolerate the highest concentration (i.e., 400 ppm) of lead. In addition to the above six fungal strains, Aspergillus ustus var. ustus (Bainier) Thom and Church could tolerate and grew well on the media with moderate concentrations (200 ppm) of lead nitrate. Cladosporium herbarum var. herbarum (Pers.) Link, Curvularia sp. Boedijn, Scopulariopsis brevicaulis var. brevicaulis (Sacc.) Bainier and Scopulariopsis communis var. communis Svilv. are moderately resistant as these could grow and flourish at 40 ppm concentration only. Fusarium sp. (isolate-III) Link cannot tolerate even low doses of lead nitrate. Out of these 19 species, 5 fungal species, i.e., Aspergillus candidus, Aspergillus niger, Penicillium implicatum, Sepedonium chrysospermum and Trichoderma lignorum were selected for studying the effect of different concentrations of lead nitrate on the in vitro growth of individual species. Thus, these species can be further tried for their utilization as biosorbents for remediation of lead in the effluents.