Pseudomonas aeruginosa is a versatile pathogenic bacterium that can cause potentially fatal infections for those with weakened immune systems. P. aeruginosa poses a serious threat in clinical settings due to its ability to colonize in respirators and catheters, and its resistance to many antibiotics makes infections difficult to treat. A research team at the University of Geneva (UNIGE) have developed a new method to potentially fight P. aeruginosa infections, by targeting a previously unknown regulator of gene expression that contributes to the bacterium’s dangerous nature.
The team combined molecular genetic and biochemical approaches to determine the function of a certain RNA helicase in P. aeruginosa known as RhlE2, including RNA sequencing and pull-down assays combined with SDS-PAGE and Orbitrap mass spectrometry. In vitro tests showed that RhlE2 contributed to changes in gene expression affecting the bacterium’s virulence, but that the bacteria was still able to multiply normally in the absence of this RNA helicase.
To understand the protein’s impact in vivo, scientists infected Galleria mellonella larvae with P. aeruginosa and found that 90% of larvae infected with a strain that had the RhlE2 gene removed survived after 20 hours, while less than 20% of larvae survived being infected with a normal strain. Control larvae injected with a saline solution had a survival rate of 100%. The research was published in Nucleic Acid Research.
“This protein controls the degradation of numerous messenger RNAs coding for virulence factors,” said Martina Valentini, of the Department of Microbiology and Molecular Medicine at UNIGE. “From an antimicrobial drug strategy point of view, switching off the pathogen’s virulence factors rather than trying to eliminate the pathogen completely, means allowing the host immune system to naturally neutralise the bacterium and potentially reduces the risk for the development of resistance. Indeed, if we try to kill the bacteria at all costs, the bacteria will adapt to survive, which favours the appearance of resistant strains.”
The research team is continuing its work by screening a series of known drug molecules to determine whether any have the capacity to selectively block RhlE2. The team is also studying in detail the inhibition mechanisms on which a drug development strategy could be based.
Photo: Surface architecture of a Pseudomonas aeruginosa colony grown for three days on semi-solid medium (stereomicroscope, artificial color). Credit: UNIGE