Nucleoside uptake inVibrio choleraeand its role in the transition fitness from host to environment

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As it became evident recently, extracellular DNA could be a versatile nutrient source of the facultative pathogenVibrio choleraealong the different stages of its life cycle. By the use of two extracellular nucleases and periplasmic phosphatases,V. choleraedegrades extracellular DNA to nucleosides. In this study, we investigated the nucleoside uptake via identification and characterization of VCA0179, VC1953 and VC2352 representing the three nucleoside transport systems inV. cholerae. Based on our results VC2352 seems to be the dominant nucleoside transporter. Nevertheless, all three transporters are functional and can contribute to the utilization of nucleosides as a sole source of carbon or nitrogen. We found that the transcriptional activity of these three distal genes is equally promoted or antagonized by CRP or CytR respectively. Finally, mutants impaired for nucleoside uptake exhibit decreased transition fitness from the host into low carbon environments along the life cycle ofV. cholerae.

Extracellular DNA represents an abundant biopolymer of theVibrio choleraebiofilm matrix and can be degraded to the nucleoside level by extracellular nucleases and phosphatases. We characterized three functional nucleoside transport systems, which contribute to the utilization of nucleosides as a nutrient source, and play a physiological role along the lifecycle ofV. cholerae. Impaired nucleoside uptake not only alters biofilm formation, but also reduces survival fitness from the host into low carbon environments.

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