Antibacterial Activity of Cyanobacteria Dolichospermum affine Isolated from Freshwater

Cyanobacteria are known for their potential for antibacterial activity against a variety of pathogens, which are of medicinal importance in drug development. In addition, Cyanobacterial species produce various secondary metabolites that are used as dye and pigmentation and food additives. Cyanobacteria Dolichospermum affine (Lemmermann) Wacklin, L. Hoffmann & Komarek was isolated from freshwater resources and its antimicrobial effect was studied. Chloroform, methanol and water extracts of D. affine were tested to investigate their efficiency against five pathogenic bacterial strains [Pseudomonas aeruginosa (ATCC 27853), Shigella dysenteriae (ATCC 11835), Escherichia coli (ATCC 25924), Staphylococcus aureus (ATCC 29213) and Bacillus subtilis (ATCC 6633)]. The antimicrobial test was determined using the disk diffusion method. The antimicrobial activities of D. affine extracts were measured using the diameter of the inhibition zone (DIZ) of the pathogen microorganisms. The results showed that B. subtilis and E.coli were more sensitive, while S. aureus and P. aeruginosa showed more intermediate results. The highest antimicrobial activity was measured against E. coli (DIZ=13.9±0.05 mm - methanol), followed by B. subtilis (DIZ=13.6±0.05 mm - methanol). The lowest antibacterial effect of D. affine extracts were observed against P. aeruginosa (DIZ=11.7±0.02 mm - chloroform) and S. aureus (DIZ=12.2±0.03 mm - chloroform). The Gram-negative bacteria S. dysenteria exhibited no zone of inhibition. The aqueous extract showed poor activities against the tested pathogenic bacteria. Therefore, this study revealed that D. affine extracts would be a promising natural resource for new antibiotics and further research would be needed.