PvdQ acylases in fluorescent pseudomonads

PhD ceremony: Mr. P. Nadal Jimenez, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen

Title: PvdQ acylases in fluorescent pseudomonads

Promotor(s): prof. W.J. Quax

Faculty: Mathematics and Natural Sciences

The research presented by Pol Nadal Jimenez in his thesis investigates the role of the quorum quenching acylase PvdQ in fluorescent pseudomonads. PvdQ is an Ntn-hydrolase member capable of degrading N-acyl homoserine lactones (AHLs), the major group of molecules used for cell-to-cell communication in Gram-negative bacteria (quorum sensing). One of the most relevant actions coordinated by quorum sensing in bacteria is infection. By assessing their population density, bacteria invading a host are capable of determining the optimal moment to start producing virulence factors with a chance to overcome the host severely compromising the outcome of the infection.

On one hand, the work of Nadal Jimenez has aided to the structure elucidation of PvdQ, a quorum quenching acylase produced by fluorescent pseudomonads capable of degrading long chain (AHLs). This work provides valuable insights into the mechanism that PvdQ uses to recognize and degrade communication signals and strengths the potential in the use of these enzymes against infections.

On the other, his research has aimed to solve the question: “why does P. aeruginosa produce an enzyme capable of disrupting its own communication systems?” The results provided in his work revealed that the major role of PvdQ is likely to be participating in the biosynthesis of pyoverdine, the major siderophore in fluorescent pseudomonads. Supporting this hypothesis there is the fact that while bacteria generally produce AHLs constitutively, PvdQ is only produced when iron availability is low. In that context, P. aeruginosa is the exception rather than the rule being the only member of its group exploiting the quorum quenching capabilities of this enzyme for regulation of its own communication systems.