Heavy metal tolerance of filamentous fungi isolated from polluted sites in Tangier, Morocco

Thirty-six micro-organisms, represented by fungi and yeasts strains, were isolated from heavy metal-contaminated sites in Tangier, Morocco. Filamentous fungi isolated belonged to the genera Aspergillus, Penicillium, Fusarium, Alternaria andGeotrichum. They were screened for their resistance to heavy metals. The results revealed that the majority of the isolates were resistant to Pb, Cr, Cu and Zn, whereas to Cd, only the fungus Penicillium sp. was able to grow. The level of resistance depended on the isolate tested, as well as the site of its isolation. Minimum inhibitory concentrations (MICs) for Pb2+, Cr6+, Cu2+ and Zn2+ were also determined. Aspergillus and Penicillium isolates were the most tolerant to the heavy metals and exhibited strong growth, often exceeding the control (isolates grown in agar medium without heavy metals). Their MIC ranged from 20 - 25 mM for Pb, followed by 15 - 20 mM both for Cu and Zn and 10 - 15 mM for Cr. These fungi have shown a high level of resistance to all metals tested, which makes them attractive potential candidates for further investigations regarding their ability to remove metals from contaminated wastewaters.   Key words: Metal tolerance, resistance, heavy metal, soil and water fungi, biosorption.