engleski

Tobramycin role in inter-species signaling by affecting the RhlI/R quorum sensing system in P. aeruginosa.

In environment bacteria live in mixed communities with other prokaryotes and there is probably considerable competition among them, as well as constant communication. It is assumed that antibiotics with inhibitory activity are important as weapons in inter-microbial competition, but recently it has been shown that antibiotics have functional interactions with cellular processes, which are different from the primary inhibitory effect. Several studies have shown that subinhibitory concentrations (SICs) of antibiotics can transcriptionally modulate a large number of genes. In this study we determined the effect of SICs of tobramycin on quorum sensing systems in an environmental isolate of P. aeruginosa PUPa3. It was established that SICs of tobramycin inhibited the RhlI/R system by reducing levels of C4-HSL production and altered phenotypes related to quorum sensing such as swarming, biofilm formation, proteolytic activity and pyocyanin production. This effect was not due to a decrease of rhlI transcription and it required tobramycin-ribosome interaction. It is reasonable to assume that P. aeruginosa encounters tobramycin in nature, since it is produced by its niche mate Streptomyces tenebrarius. Understanding the tobramycin response by an environmental P. aeruginosa strain will highlight possible inter-species signaling taking place in nature.

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

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