Abstract
Lichen (Collema auriforme) collected from Kolli Hills of Tamil Nadu, India and two symbiotic cyanobacteria (Aphanocapsa sp. NTK28, and Nostoc sp. NTK29) were taken for screening antibacterial activity. Alcohol and acetone were used as solvents for extraction of compounds from lichen and symbiotic cyanobacteria. Four clinical isolates of Pseudomonas sp., Escherischia coli, Klebsiella sp., and the Gram positive organism Staphylococcus sp. were used as test organisms. Solvent extracts of lichen showed antibacterial activity against three test organisms. Alcohol extract of lichen showed no inhibitory effect on Pseudomonas sp. Other organisms like E. coli, Klebsiella sp. and Staphylococcus sp. were highly susceptible to alcoholic extract even at low concentration. Solvent extracts (alcohol and acetone) of cyanobacteria did not show any significant effect on the selected bacterial strains.