engleski

Aminoglycoside antibiotic tobramycin as a signaling agent of quorum sensing in Pseudomonas aeruginosa environmental isolate

Antibiotics help bacteria to fight against their competitors in nature, however, it has been shown recently that at low concentrations they can also act as signaling molecules affecting gene expression in bacterial communities. A few studies have shown that subinhibitory concentrations (SICs) of tobramycin induce biofilm formation and enhance the capabilities of P. aeruginosa to colonize specific environments. We have used environmental P. aeruginosa strain PUPa3 in our studies because is reasonable to assume that P. aeruginosa encounters tobramycin in nature since it is produced by its niche mate Streptomyces tenebrarius. P. aeruginosa PUPa3 was grown in the presence of different concentrations of tobramycin and it was determined at which highest concentration SIC growth, total protein levels and translation efficiency were not affected. At SIC it was then established if phenotypes related to cell-cell signaling known as quorum sensing were altered. We determined whether tobramycin sensing/response at SICs affected the two independent AHL quorum sensing systems in P. aeruginosa PUPa3. It was established that SICs of tobramycin inhibited the RhlI/R system by reducing levels of C4-HSL production. This effect was not due to a decrease of rhlI transcription and required tobramycin-ribosome interaction. Tobramycin signaling in P. aeruginosa environmental isolate shows that different strains found in nature and in clinical settings can have a different response to the antibiotics as signaling molecules. Learning the response of P. aeruginosa to subinhibitory concentrations of antibiotics is thus a relevant task for understanding the biological responses of this bacterium in patients under treatment of the tobramycin, as well as it can highlight possible inter-species signaling that is taking place in nature.

quorum sensing; tobramycin; Pseudomonas aeruginosa PUPa3; aminoglycoside resistance methyltransferases

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