The Antimicrobial Potential of Actinomycetes Isolated from Marine Soils in Tyre City Beach, Lebanon: A Promising Source of Novel Bioactive Metabolites

The development of extensive antibiotic resistance has created an urgent demand to identify novel sources of antimicrobial agents. Interest in actinomycetes has become prevalent around the world because of their ability to generate several beneficial bioactive metabolites. In the present study, 32 marine soil samples were collected from Tyre City Beach, Lebanon, in different seasons. A total of 10 actinomycetes species were identified and characterized depending on their microscopic features. All isolates were tested for their potential to exert antimicrobial activities against varied microorganisms using cross-streak and agar well diffusion methods. All isolates displayed significant antimicrobial activities against the tested indicator microorganisms. Similarly, all 10 isolates of marine actinomycetes exhibited antifungal activity in cross-streak tests against Candida albicans, Aspergillus niger, and Aspergillus flavus. Moreover, the optimum conditions used to enhance the production of antimicrobial secondary metabolites against Bacillus cereus were tested for the three isolates Kocuria rosea, Micrococcus luteus, and Streptomyces longisporoflavus. Our results indicate that actinomycetes isolated from Tyre City Beach, Lebanon, represent a promising source of antimicrobial bioactive substances.