Abstract:
A total of 54 actinomycete isolates were obtained from terrestrial,
brackish and marine sediment samples collected from Barangay
San Isidro, Babak District, Samal Island. These were then tested for
antagonistic activity against four test microorganisms: E. coli EC-7,
S. aureus SA-12, C. utilis CU-14 and A. niger AN-20. Results indicated
that 14 isolates were active against at least one of the test microorganisms,
13 of which were active against at least one test bacteria, and four against
at least one test fungi. From these, it was noted that the terrestrial site was
the richest source of antibiotic-producing actinomycetes wherein 52.17%
of the terrestrial isolates were antibacterial and 13.04% were antifungal.
No marine isolate was found active against the test microorganisms while
one brackish isolate was found to be inhibitory. The upper 50% of the
bioactive actinomycete isolates were further screened against other strains
of the test microorganisms. Three out of the seven isolates exhibited
antagonistic activity. Based on the mean diameter of inhibition zones, ti5
was chosen to be the most potent actinomycete isolate. It was subjected to
the minimum inhibitory concentration assay, cultural characterization and
morphological characterization. The minimum inhibitory concentration of
ti5 was determined to be about 20% to 25%. Cultural and morphological
characterization suggested that it belongs to the genus Micromonospora.
The large number of actinomycetes with persistent antimicrobial activity
qualifies Samal Island sediments as a potential source of novel antibiotics.
