Azetidine‐Containing Alkaloids Produced by a Quorum‐Sensing Regulated Nonribosomal Peptide Synthetase Pathway in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa displays an impressive metabolic versatility, which ensures its survival in diverse environments. Reported herein is the identification of rare azetidine‐containing alkaloids from P. aeruginosa PAO1, termed azetidomonamides, which are derived from a conserved, quorum‐sensing regulated nonribosomal peptide synthetase (NRPS) pathway. Biosynthesis of the azetidine motif has been elucidated by gene inactivation, feeding experiments, and biochemical characterization in vitro, which involves a new S‐adenosylmethionine‐dependent enzyme to produce azetidine 2‐carboxylic acid as an unusual building block of NRPS. The mutants of P. aeruginosa unable to produce azetidomonamides had an advantage in growth at high cell density in vitro and displayed rapid virulence in Galleria mellonella model, inferring functional roles of azetidomonamides in the host adaptation. This work opens the avenue to study the biological functions of azetidomonamides and related compounds in pathogenic and environmental bacteria.

Genetic and Transcriptomic Characteristics of RhlR-Dependent Quorum Sensing in Cystic Fibrosis Isolates of Pseudomonas aeruginosa

“…The only gene in the core regulon annotated as a downstream transcriptional regulator is vqsR (PA2591). Making up nearly half of the core regulon, the RhlR-regulated genes spanning PA3326 to -3334 encode a recently described azetidomonamide ( aze ) biosynthesis regulon (PA3331 is RhlR regulated in 4/5 isolates) ( 41 , 42 ). Finally, the core regulon also includes genes coding for two hypothetical proteins (PA1221 and PA4141).…”

Non-hierarchical, RhlR-regulated acyl-homoserine lactone quorum sensing in a cystic fibrosis isolate ofPseudomonas aeruginosa

“…Among the most highly regulated genes [3,28] were those belonging to a conserved nonribosomal peptide synthetase (NRPS) pathway (PaE90_1770-1779; PA3327-3336). The products of this NRPS pathway have been identified as azetidine-containing alkaloids referred to as azetidomonamides[38]. The biological significance of this widely conserved NRPS pathway in Pseudomonas species or what roles azetidomonamides may play in virulence or interspecies interaction is not well understood, but regulation by QS appears to be a common feature.…”

ClpP1P2 peptidase activity promotes biofilm formation in Pseudomonas aeruginosa

“…Furthermore, instead of clustering on the genome with other protein quality control enzymes like clpP1 , clpP2 maps to a gene cluster called aze that appears to be a mobile genetic island. Genes at this locus are also controlled by quorum sensing and have recently been shown to synthesize a modified nonribosomal peptide called azetidomonamide B or azabicyclene (Hong et al, 2019; Patteson et al, 2019). Genes homologous to clpP2 and aze are clustered in several bacterial genomes, which suggest a potential functional relationship that remains to be explored.…”