Paracoccus Denitrificans Can Utilize Various Long-chain N-acyl Homoserine Lactones and Sequester Them in Membrane Vesicles

Many gram-negative bacteria utilize N-acyl homoserine lactone (AHL) signals to communicate with each other. Once they have been released, these signals are assumed to be shared among the population in the local environment. In contrast to this canonical quorum-sensing (QS) model, recent study in Paracoccus denitrificans showed that they can traffic their signals to each other via membrane vesicles (MVs). Here, we demonstrate that various long-chain AHLs inhibited cell aggregation in P. denitrificans, whereas the short-chain AHLs alone did not. Furthermore, MVs released from P. denitrificans were able to take up the long-chain AHLs from the environment into MVs. The AHLs associated with MVs triggered gene expression in P. denitrificans, indicating their role in QS. Our results suggest that P. denitrificans can sequester the AHL produced by other bacteria and deliver the signals to themselves via MVs. Utilizing the signals from other bacteria may be advantageous for P. denitrificans to reach the threshold QS concentration in a polymicrobial community in which the population of its own species is relatively low.