Antibacterial activity of two soil cyanobacteria Nostoc polludosum and Cylindrospermum licheniforme

Antibacterial activity of two cyanobacterial strains i.e. Nostoc polludosum and Cylindrospermum licheniforme was studied. Both cyanobacterial strains were isolated from agricultural fields of Varanasi, India. Crude extracts of both strains in five solvents i.e. Ethanol, Petroleum ether, Acetone, Methanol, and Chloroform were screened against two human pathogenic bacteria i.e. S. aureus and E. coli. Crude extracts of each strain showed the differential antibacterial response to test organisms. Crude extract only in Acetone of Nostoc polludosum showed antibacterial activity against E. coli and no antibacterial activity was noticed against S. aureus. Acetone extract of Nostoc polludosum showed maximum inhibition zone of 11.3±0.45 mm against E. coli which is near approximately twice the antibacterial activity due to the standard antibiotic. Crude extract, only in four organic solvents i.e. Ethanol, Methanol, Acetone & Petroleum ether of Cylindrospermum licheniforme showed antibacterial activity against S. aureus and E. coli, but in all extracts, the antibacterial activity was less than the standard antibiotic. Findings of experiment suggested that acetone extract of Nostoc poludossum was suitable for mining of antibacterial agent against E. coli.