Abstract
The alkyl-4-quinolones (AQs) are a class of metabolites produced primarily by members of the Pseudomonas and Burkholderia genera, consisting of a 4-quinolone core substituted by a range of pendant groups, most commonly at the C-2 position. The history of this class of compounds dates back to the 1940s, when a range of alkylquinolones with notable antibiotic properties were first isolated from Pseudomonas aeruginosa. More recently, it was discovered that an alkylquinolone derivative, the Pseudomonas Quinolone Signal (PQS) plays a key role in bacterial communication and quorum sensing in Pseudomonas aeruginosa. Many of the best-studied examples contain simple hydrocarbon side-chains, but more recent studies have revealed a wide range of structurally diverse examples from multiple bacterial genera, including those with aromatic, isoprenoid, or sulfur-containing side-chains. In addition to their well-known antimicrobial properties, alkylquinolones have been reported with antimalarial, antifungal, antialgal, and antioxidant properties. Here we review the structural diversity and biological activity of these intriguing metabolites.
Highlights
The bacterial alkylquinolones are a class of microbial metabolites consisting of a 4-quinolone core, typically substituted with alkyl groups, most often at the 2 position [1]
Alkylquinolones with 1, and 4-11-carbon linear chains have been isolated and fully. While these are most strongly associated with the Pseudomonas genus, examples have been characterized, MS-basedPseudoalteromonas, studies have detected the presence of quinolone with reported fromthough the Alteromonas, and Burkholderia genera (Table A1). derivatives
One of the first of these studies was conducted by Taylor et al in 1995, where GCMS profiling of a clinical isolate of Pseudomonas aeruginosa revealed the presence of a large number of alkylquinolones (Table A3) [20]
Summary
The bacterial alkylquinolones are a class of microbial metabolites consisting of a 4-quinolone core, typically substituted with alkyl groups, most often at the 2 position [1]. The best-known of these are the Pseudomonas Quinolone Signal (PQS, O7), a potent modulator of quorum sensing behaviour in the Pseudomonas genus, and its biosynthetic precursor, 4-hydroxy-2-heptylquinoline (HHQ, H7). The discovery of these alkylquinolones begin with the use of a Pseudomonas aeruginosa (Bacillus pyocyaneus) extract by Bouchard for the prevention of anthrax in rabbits [2]. Because they were often in a species-specific manner Several of these alkylquinolones were named because predominantly produced by P. aeruginosa [11]. Aeruginosa was not solely a function of the homoserine lactones
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