Enzymatic Degradation of Bacterial Quorum Sensing

Pseudomonas aeruginosa, a Gram-negative bacterium, is an opportunistic pathogen able to infect animals, plants and humans. This bacterium has been associated with several types of infections causing a major threat to immunocompromised, severely burned and cystic fibrosis patients.

P. aeruginosa is able to secrete various signalling molecules, such as N-acyl-homoserine lactones (AHLs), which control the production of many virulence factors, including toxins and biofilms, making it highly pathogenic and resistant towards antibiotic treatment. The production of these virulence factors is under the control of a communication system known as quorum sensing. Quorum sensing is used by a number of bacteria to co-ordinate their behavior, according to their local population density. At low cell density, the bacterium secretes very low levels of signaling molecules, however, when the cell density increases, higher amounts of the signaling molecules are produced, and when a threshold is reached then production of the virulence factors is initiated. It’s by no surprise, that quorum sensing became an interesting target since the disruption of this communication system (a process known as quorum quenching) can lead to a more effective antibiotic treatment. The discovery of two different types of enzymes able to break AHLs was a big step towards quorum quenching. The first type of these enzymes, AHL-lactonases, is capable of cleaving the lactone ring, while the second type, AHL-acylases, is active against the acyl-chain of the signaling molecule.

Objectives

In the search for novel antimicrobials, we have based our efforts in the development of potent quorum quenchers that allow us to effectively interfere with these communication systems to obtain an advantage in the fight against infection. We are actually studying the effects of these quenchers using pvdQ, an acylase from P. aeruginosa, as a model to create potent enzymatic variants with enhanced quorum quenching activity. In the past years we have characterized PvdQ and proved its protective activity against Pseudomonas aeruginosa infection in Caenorhabditis elegans model. In addition, we generated PvdQ mutant able to degrade shorter-chain AHL important for Burkholderia cenocepacia, indicating its potential activity towards infection of this bacterium.

Research Techniques

• protein purification (FPLC),
• enzymatic activity assay,
• drug formulation
• development of P. aeruginosa infection and drug administration to mice model

Projects

Formulation of PvdQ and examination of its therapeutic activity against Pseudomonas aeruginosa in mice models.

For further information please contact Putri Dwi Utari MSc., Dept. of Pharmaceutical Biology, GRIP, building 3215-room 9.65, Antonius Deusinglaan 1, 9713 AV GRONINGEN.

Additional information on these topics can also be obtained from Prof.dr. Wim J. Quax , professor Department of Pharmaceutical Biology