2,5-Dialkylresorcinol Biosynthesis in Pseudomonas aurantiaca : Novel Head-to-Head Condensation of Two Fatty Acid-Derived Precursors

Abstract

2-Hexyl-5-propylresorcinol is the predominant analog of several dialkylresorcinols produced by Pseudomonas aurantiaca (Pseudomonas fluorescens BL915). We isolated and characterized three biosynthetic genes that encode an acyl carrier protein, a ␤-ketoacyl-acyl carrier protein synthase III, and a protein of unknown function, all of which collectively allow heterologous production of 2-hexyl-5-propylresorcinol in Escherichia coli. Two regulatory genes exhibiting similarity to members of the AraC family of transcriptional regulators are also present in the identified gene cluster. Based on the deduced functions of the proteins encoded by the gene cluster and the observed incorporation of labeled carbons from octanoic acid into 2-hexyl-5-propylresorcinol, we propose that dialkylresorcinols are derived from medium-chain-length fatty acids by an unusual head-tohead condensation of ␤-ketoacyl thioester intermediates. Genomic evidence suggests that there is a similar pathway for the biosynthesis of the flexirubin-type pigments in certain bacteria belonging to the order Cytophagales.

darR and darS are regulatory genes that modulate 2-hexyl, 5-propyl resorcinol transcription in Pseudomonas chlororaphis PCL1606

“…The biosynthetic mutant genes DdarA and DdarB and the derivative mutant in gacS showed a complete loss of HPR production. The derivative mutant of the biosynthetic gene darC showed antifungal activity, likely reflecting the function of darC, a carrier of acyl intermediates during fatty acid synthesis (Byers & Gong, 2007), determined through the complementation of similar proteins inside the cell (Nowak- Thompson et al, 2003). Moreover, the transcriptional regulators darS and darR reduce HPR production, but only to half of the amount produced in the WT strain.…”

“…auranthiaca BL915. In this strain, the genes responsible for HPR production are located in a cluster containing three presumptive biosynthetic genes (darA, darB and darC), followed by two independent sequences homologous to the regulatory genes from the AraC/XylS family (darS and darR; Nowak- Thompson et al, 2003). This dar cluster has recently been identified in P. chlororaphis PCL1606 (Calderó n et al, 2013).…”

Biosynthesis‐Assisted Structural Elucidation of the Bartolosides, Chlorinated Aromatic Glycolipids from Cyanobacteria

“…We designated this region to be the bartoloside (brt) gene cluster (GenBank: KR059027). In contrast to previously characterized darAB-containing gene clusters, [10][11][12] the brt cluster lacks a designated ACP, suggesting the use of a trans-acting ACP or ACP thioesters from fatty acid biosynthesis. The participation of acyl-CoA substrates is unlikely as cyanobacteria, including S. salina LEGE 06155, lack a canonical β-oxidation pathway.…”

“…In other bacteria, a ketosynthase (DarB) and a putative aromatase (DarA) have been shown to synthesize DAR scaffolds in a convergent process. [10] DarB catalyzes the head-to-head condensation of a β-ketoacyl acyl carrier protein (ACP) thioester with an α,β-unsaturated acyl ACP thioester, resulting in a dialkylcyclohexanedione carboxylic acid (carboxy-CHD). [11] DarA is thought to be an aromatase based on its in vivo activity in a heterologous host, [11] but has not been characterized in vitro.…”

Characterization of a Phenazine and Hexanoyl Homoserine Lactone Producing Pseudomonas aurantiaca Strain PB-St2, Isolated from Sugarcane Stem

“…Earlier studies have reported the production of various antifungal compounds including phenazine and its derivatives (i.e., 1-oxyphenazine, phenazine-1,6,dicarboxylate, and 2-hexyl-5-propyl-alkylresorcinol) by P. aurantiaca [4,18]. Recently, Mandryk et al [12] reported new antimicrobial compounds produced by this bacteria, having molecular formulas of C 18 H 36 NO (molecular weight 282.8; antibacterial activity) and C 20 H 31 O 3 (molecular weight 319.3; antifungal activity).…”