Antibacterial and Antifungal Activities of Gelatinose and non-Gelatinose Lichen Species

Abstract

Background: Despite the wide diversity of the basic growth forms (crustose, squamulose, foliose, and fruticose), all lichens have a similar internal morphology. The bulk of the lichen’s body is formed from filaments of the fungal partner, and the relative density of these filaments defines the layers within the lichen. Objectives: To continue and complete the previous study, this study was designed to assess the antibacterial and antifungal activity of different extractions of lichens. Materials and Methods: Acetone, methanol and aqueous extractions of the lichens, including Acarospora strigata, Collema crispum, Placidium squamulosum, Physcia biziana, Lecanora prophetae-eliae and Ramalina farinacea, were evaluated in vitro against seven bacterial strains (Escherichia coli ATCC1652, Salmonella typhi ATCC1679, Proteus mirabilis ATCC2601, Staphylococcus aureus ATCC1885, Enterococcus faecalis ATCC2321, Staphylococcus epidermidis ATCC2405, and Bacillus cereus ATCC13061), and two fungi (Verticillium dahlia, Fusarium moniliforme). The antibacterial activity was estimated via disc diffusion method and the minimal inhibitory concentration (MIC) was determined via broth tube dilution method. Results: Among the six tested lichens, methanol extracts of P. squamulosum, P. biziana, and L. prophetae-eliae showed relatively high antibacterial activities and also the acetone extraction of L. prophetae-eliae showed antibacterial activity against S. epidermidis and B. cereus. The bacteria were more sensitive than the fungi. The methanol extract of P. squamulosum showed the highest antibacterial activity; besides, the least amount of MIC value was 250 mg/mL. Conclusions: It seems that the tested lichens could be effective as antibiotics; especially, in terms of drug resistance, they can be proper substitutes; but, further studies are suggested.