Biochemical characterization of antibiotic producing actinomycetes isolated from tobacco contaminated soil

Isolation of antibiotic producing actinomycetes is useful in identifying the compounds responsible for antibacterial activity. The aim of this study was to explore the biochemical characterization of antibiotic producing actinomycetes and to evaluate the antibacterial activity of the actinomycetes against Staphylococcus aureus. In this particular study starch casein agar was used to isolate actinomycetes from tobacco contaminated soil in Zimbabwe. Four different colonies were identified based on morphology. The different colored colonies observed were pink, white, off-white and green. The colonies were further classified under microscope using iodine crystal. White colonies showed rod shaped cells with no external features, off-white colonies had non-branched sporulating mycelium whereas green colonies exhibited sporulating mycelium with vegetative features and pink colonies were spherical shaped cells with no external features. All of the four colonies were gram positive and were positive for the catalase test. The four different colonies were also positive for the lipase test whereas only the white, off-white and green colonies were positive for the methyl red test. Zones of inhibition were observed in well diffusion assays for antibacterial tests of these actinomycetes (green, white, off-white and pink colonies) against S. aureus. Thus, this study shows that some actinomycetes have antibacterial activity and may therefore be used as sources of antibacterial agents