Screening of Antibiotic-Producing Actinomycetes from Marine, Brackish and Terrestrial Sediments of Samal Island, Philippines

Abstract

This study screened actinomycetes isolated from marine, brackish and terrestrial sediments of San Isidro, Babak District, Island Garden City of Samal, Davao del Norte for antimicrobial activity. A total of 54 actinomycetes isolates were obtained from the various sediment samples collected and were then tested for antagonistic activity against Escherichia coli , Staphylococcus aureus , Candida utilis and Aspergillus niger . Results indicated that 14 out of 54 isolates were active against at least one of the test microorganisms, 13 were active against at least one test bacteria, and four was active against at least one test fungi. It was noted that the terrestrial site was the richest source of antibiotic-producing actinomycetes where approximately 52% of the isolates were antibacterial and 13% were antifungal. No marine isolate was found active against the test microorganisms while one brackish isolate was found to be inhibitory. Selected bioactive isolates were chosen to be further screened against other strains of the test microorganisms during the secondary screening. Resulting mean diameter of inhibition zones revealed isolate ti5 as the most potent of all the isolates with a minimum inhibitory microbial concentration of 20% (MIC). Cultural and morphological characterization classified it under the genus Micromonospora . It can be recommended therefore that marine, brackish and terrestrial sediments of San Isidro, Babak District, Island Garden City of Samal be further investigated for antibiotic-producing actinomycetes. The number of actinomycetes isolated with persistent antimicrobial activity isolated suggests that Samal Island sediments may be a potential source of novel antibiotics. Keywords: antimicrobial, actinomycetes, Samal Island, minimum inhibitory concentration DOI = 10.3860/jrsce.v4i3.631 Journal of Research in Science, Computing, and Engineering 4 :3 (2007), pp. 29-38