Pseudomonas Quinolone Signal (PQS) probes capture a new binding partner for this signal molecule.

Over the last two decades, tens of millions of dollars have been invested in understanding virulence in the human pathogen, Pseudomonas aeruginosa. However, the top 'hits' obtained in a recent TnSeq analysis aimed at identifying those genes that are conditionally essential for infection did not include most of the known virulence factors identified in these earlier studies. Instead, it seems that P. aeruginosa faces metabolic challenges in vivo, and unless it can overcome these, it fails to thrive and is cleared from the host. In this review, we look at the kinds of metabolic pathways that the pathogen seems to find essential, and comment on how this knowledge might be therapeutically exploited.

1IntroductionSince its discovery and initial characterization some 15 years ago by Pesci et al., [1] one particular class of Pseudomonasa eruginosa intercellulars ignaling molecules,t he 4-alkylquinolones (AQs), and the genes involved in the synthesiso ft hese molecules,h ave appeared with refreshing regularity in many studies involving this organism. Herein, we presentahistorical overview of how alkyl quinolones and their signaling pathways were discovered, what these molecules do,w hat gaps remain in our knowledge,a nd how researchers are manipulating AQ signaling for potential therapeutic benefit. Ther eview is not intended to be exhaustive or detailed-the reader is referred to several other excellent monographs for those purposes; [2][3][4] instead, it is intended to providea"taster" of the field and some insights into unresolved questions.ments (las and rhl) of the P. aeruginosa N-acylhomoserine lactone-dependent QS signaling pathways. Herein, we present the discovery and elucidationo fP QS signaling from ah istorical perspective, and also outlines ome of the outstanding research questionst hat still need to be addressed. Finally,w es how how ab etter understanding of the biochemistry underpinning this pathway is leading to the development of new antimicrobial interventions with clear therapeutic potential.Keywords: antimicrobial agents · biological activity · Pseudomonas quinolone signal · quorum sensing · virulence[a] T. Sams

Recently reported DNA nanoflowers are an interesting class of organic-inorganic hybrid materials which are prepared using DNA polymerases. DNA nanoflowers combine the high surface area and scaffolding of inorganic Mg2P2O7 nanocrystals with the targeting properties of DNA, whilst adding enzymatic stability and enhanced cellular uptake. We have investigated conditions for chemically modifying the inorganic core of these nanoflowers through substitution of Mg2+ with Mn2+, Co2+ or Zn2+ and have characterized the resulting particles. These have a range of novel nanoarchitectures, retain the enzymatic stability of their magnesium counterparts and the Co2+ and Mn2+ DNA nanoflowers have added magnetic properties. We investigate conditions to control different morphologies, DNA content, hybridization properties, and size. Additionally, we show that DNA nanoflower production is not limited to Ф29 DNA polymerase and that the choice of polymerase can influence the DNA length within the constructs. We anticipate that the added control of structure, size and chemistry will enhance future applications.

Abstract:Pseudomonas aeruginosa is a human pathogen associated with a variety of life-threatening nosocomial infections. This organism produces a range of virulence factors which actively cause damage to host tissues. One such virulence factor is pyocyanin, known to play a crucial role in the pathogenesis of P. aeruginosa infections. Previous studies had identified a novel compound capable of strongly inhibiting the production of pyocyanin. It was postulated that this inhibition results from modulation of an intercellular communication system termed quorum sensing, via direct binding of the compound with the LasR protein receptor. This raised the possibility that the compound could be an antagonist of quorum sensing in P. aeruginosa, which could have important implications as this intercellular signaling mechanism is known to regulate many additional facets of P. aeruginosa pathogenicity. However, there was no direct evidence for the binding of the active compound to LasR (or any other targets). Herein we describe the design and synthesis of a biotin-tagged version of the active compound. This could potentially be used as an affinity-based chemical probe to ascertain, in a direct fashion, the active compound's macromolecular biological targets, and thus better delineate the mechanism by which it reduces the level of pyocyanin production.