Evaluation of biological activities from algae and their coexisting bacteria

Abstract

Marine macroalgae and their associated microorganisms are increasingly recognized as valuable sources of natural bioactive compounds. This study investigates the antibacterial potential of various algal specimens and the microbial communities naturally associated with them, collected from diverse aquatic environments in northeastern Algeria. The work combines morphological analysis, microbiological isolation, and antimicrobial assays to evaluate their biological activity. Algal samples were cultivated and analyzed under controlled laboratory conditions. Bacterial strains were isolated from the surface of algae and tested for their ability to inhibit selected pathogenic microorganisms. In addition, the direct antibacterial effect of the algal material itself was assessed using standardized in vitro techniques. The results demonstrated that both the algae and their associated bacteria possess significant antibacterial properties. Several isolates produced measurable zones of inhibition, while algal extracts also exhibited inhibitory effects against common human pathogens. These findings confirm the presence of bioactive substances and suggest a potential synergistic interaction between algae and their microbiota. Environmental factors such as salinity and nutrient conditions appeared to influence the expression of these bioactivities. This study provides new insight into the antimicrobial potential of algae–bacteria associations and reinforces the value of marine biodiversity as a source for natural therapeutic agents. It also highlights the ecological and biotechnological importance of studying aquatic microbial communities in underexplored regions.