Abstract

The aqueous and ethanol extracts prepared from some lichens species were evaluated for antibacterial activity against six standard strains (Escherichia coli,Pseudomonas aeruginosa, Bacillus subtilis, Klebsiella pneumoniae, Staphylococcus aureus and Staphylococcus epidermidis) and two environmental strains (Aeromonas) that were isolated from different lakes. The aqueous and ethanol extracts showed a variable range of antibacterial activity to both standard strains and environmental strains. Ethanol extracts showed better antibacterial activity than aqueous extracts. It was found that the inhibition zone of tested bacteria against extracts have changed between 07 - 15 mm (diameter of inhibition zone). Some lichen extracts have moderate antibacterial effect. Both ethanol and aqueous extracts have inhibited the growth of three bacteria. Neither aqueous extracts nor ethanol extracts were inhibited the growth of five bacteria. The aqueous extract of Peltigera polydactyla and the ethanol extract of theRamalina farinacea exhibited potent antibacterial activities.

Key words: Antibacterial activity, lichens, MTT method.