EVALUATING THE EFFECT OF HEAT-KILLED PATHOGENS ON ANTIMICROBIAL COMPOUNDS PRODUCTION IN STREPTOMYCES SP.AC117

Background and Aim: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 study the production enhancement of antimicrobial compounds in Streptomyces sp.AC117 was examined through co-cultivation with heat-killed Staphylococcus aureus and Bacillus subtilis.Methods: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.Results: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 inter-species interactions such as elicitation, signaling, and quorum sensing are not completely understood at molecular level.

Keywords:

Streptomyces , co-culture , secondary metabolites , antimicrobial compounds