Antibacterial Screening of Marine Bacteria Isolated from Sanur Beach Sediments, Denpasar-Bali

In Indonesia, bacterial infections are a serious concern, exacerbated by antibiotic resistance from bacterial mutations. To combat this, discovering novel antibacterial compounds from natural sources is vital. Marine sediments, especially, represent a rich, underexplored reservoir for such compounds. Sanur Beach is a popular tourist area with diverse marine life; however, few studies have explored the diversity of marine bacteria in its sediment. This research employed a multi-faceted approach to investigate bacterial isolates from Sanur Beach marine sediments. Bacteria were initially isolated using ISP-2, Actinomycetes Isolation Agar, and Starch-M Protein Agar. Antibacterial activity was screened via the agar block method against Staphylococcus aureus ATCC 25923, Streptococcus mutans FNCC 0405, Escherichia coli ATCC 25922, and Klebsiella pneumoniae ATCC 700603. Finally, 16S rRNA gene sequencing identified the isolate with the highest activity. Nine of ten isolates demonstrated antibacterial activity against at least one test bacterium. Isolate I-4 showed the largest inhibition zones: 16.28±0.73 mm ( S. aureus ), 19.37±0.23 mm ( S. mutans ), 19.79±0.06 mm ( E. coli ), and 14.92±0.85 mm ( K. pneumoniae ). Analysis of the16S rRNA gene sequence identified isolate I-4 as phylogenetically related to Streptomyces sp. VEL 17. This finding underscores the valuable antibacterial potential of marine-associated bacteria for synthesizing antibiotic compounds.