Introduction: Many secondary metabolites are not expressed under conventional laboratory condition because growth conditions differ from natural environment.The co-cultivation of bacteria has recently been described as a promising strategy to induce the production of novel metabolites through possible gene activation.In this studythe production enhancementofantimicrobial compounds in Streptomyces sp.AC117 was examinedthrough co-cultivation with heat-killed Staphylococcus aureus and Bacillus subtilis. Method: An overnight culture of S.aureus and B.subtilis was centrifuged and the cell numbers were adjusted to 1×108 cells/ml. The bacterial pathogen suspensions were placed in boiling water for 30 min. The heat-killed S.aureus (5% v/v) and B. subtilis (2.5% v/v) was introduced to the flask at the same time as inoculation with Streptomyces sp.AC117. Every 48 hours the extracts from pure and co-culture were evaluated with agar well diffusion method against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa. Result: The inhibition zone diameter for elicited culture with S.aureus in the first 48 hours was increased 3 mm against S.aureus, 4 mm against E.coli and 2 mm against P.aeruginosa compared to the pure extracts. The increase in inhibition zone diameter for B.subtilis elicited culture was only seen against S.aureus (4 mm). Conclusion: Since microorganisms live in a complex environment, elicitation may mimic the inter-species interactions in nature resulting in metabolic production. In general, the mechanisms of interspecies interactionssuch as elicitation, signaling, and quorum sensing are notcompletely understood at molecular level.

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