Determination of the Antibacterial Activity of Microalgae Isolated from Giresun Streams

The rapid emergence of antibiotic resistance has become a global crisis, threatening public health, food security, and agriculture. Particularly, the control of zoonotic diseases and the assurance of microbial safety in animal products necessitate the development of new and sustainable solutions. In this context, research on antimicrobial agents derived from natural sources has been gaining significant importance. Microalgae, with their ability to synthesize bioactive compounds, represent a promising natural resource in this regard. Studies on the antibacterial properties of freshwater microalgae in Türkiye remain limited. However, the rich biodiversity of these ecosystems provides valuable opportunities for the discovery of novel antimicrobial agents. This study investigates the antibacterial activity of Chlorococcum hypnosporum, Stichococcus bacillaris, Chlorella vulgaris, Chlorolilaea pamvotia, and Desmodesmus opoliensis isolated from the Aksu, Batlama, and Büyük Güre streams in Giresun, Türkiye. Bioactive compounds were extracted using acetone, ethanol, and methanol, and their antibacterial effects were tested against five bacterial strains via the agar well diffusion method. Notably, the acetone extract of Chlorella vulgaris exhibited significant activity against Bacillus subtilis at 40 µl/petri, and also showed high antibacterial activity against Escherichia coli. Additionally, the ethanol extract of Chlorococcum hypnosporum exhibited antibacterial activity against both Salmonella Typhimurium and Staphylococcus aureus. Other microalgae species also demonstrated significant antibacterial properties against the tested bacterial strains. These findings enhance our understanding of the antibacterial potential of Türkiye's freshwater microalgae and highlight their potential as sustainable antimicrobial agents for ensuring microbial safety in animal products. This study further emphasizes the importance of microalgae as natural and environmentally friendly alternatives in combating antibiotic resistance and preventing agricultural microbial contamination.