Marijana, K. & R. Branislav 2011: Antibacterial and antifungal activity of different lichens extracts and lichen acid. - Research Journal of Biotechnology 6(1): 23-26. [RLL List # 223 / Rec.# 32924] Abstract: Antibacterial and antifungal activity of the acetone, methanol and aqueous extracts of the lichens Lecanora atra, Parmelia reticulata, Parmelia oomphalodes and salazinic acid from Parmelia reticulata lichen were explored in vitro against six species of bacteria and eight species of fungi. The antimicrobal activity was estimated by the disc-difusion method and determination of the minimal inhibitory concentration (MIC) by the Broth tube dilution method. The aqueous extracts of all of the tested lichens were inactive, whereas the acetone and methanol extracts showed antimicrobial activity against the majority of the tested organisms. Among the extracts, the strongest activity was found in the acetone extract of the lichen Parmelia omphalodes where the least measured MIC value was 0.78 mg/ml. Salazinic acid also showed strong activity against bacteria and fungi. The lowest measured MIC value was 0.39 mg/mL related to the Klebsiella pneumonie species. The bacteria were more sensitive related to the tested fungi. Generally, Bacillus subtilis and Bacillus mycoides were the most sensitive of the tested bacterial species while Botrytis cinerea and Candida albicans were the most sensitive fungal species. There was no antimicrobial activity against Escerichia coli species. The results obtained show that the tested lichen and their compound demostrated a strong antimicrobal effect against the tested microorganisms.