Himalomycin A and cycloheximide-producing marine actinomycete from Lagos Lagoon soil sediment

Objective: To isolate and screen Actinomycetes from Lagos Lagoon soil sediments for antibiotic production. Methods: Soil samples were collected from four different locations of Lagos Lagoon and were dried for 2 weeks. Actinomycetes were isolated by serial dilution using spread plate method on starch casein and Kuster’s agar supplemented with 80 μg/mL cycloheximide to prevent fungal growth. The plates were incubated at 28 °C for 1-2 weeks. Isolates were selected based on their cultural characteristics as well as their Gram’s reaction and subcultured on same media for isolation and incubated at 28 °C for 3 days. Pure cultures were maintained on nutrient agar slants at 4 °C. Thereafter, they were inoculated into starch casein and Kuster’s broth media and incubated at 28 °C for 8 days. The resulting crude extracts were screened for antimicrobial activity against the following microorganisms: methicillin resistant Staphylococcus aureus, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 29522, Pseudomonas aeruginosa ATCC 27853, Candida albicans and Enterococcus faecalis ATCC 29212. Coagulasenegative staphylococci isolated from HIV patients were also used (Staphylococcus warneri, Staphylococcus xylosus and Staphylococcus epidermidis). Extraction of secondary metabolites was carried out and analysed using gas chromatography-mass spectrometer. Results: All the isolates displayed varying antimicrobial activity against at least one of the test organisms. Himalomycin A was identified in the extract from isolate ULS7. The gas chromatography-mass spectrometer data analysis showed the antibiotic profile of these isolates. Conclusions: The isolate ULS7 was found to display the highest antimicrobial activity against the test organisms.