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Pseudomonas species are known to be prolific producers of secondary metabolites that are synthesized wholly or in part by nonribosomal peptide synthetases. In an effort to identify additional nonribosomal peptides produced by these bacteria, a bioinformatics approach was used to 'mine' the genome of Pseudomonas syringae pv. tomato DC3000 for the metabolic potential to biosynthesize previously unknown nonribosomal peptides. Herein we describe the identification of a nonribosomal peptide biosynthetic gene cluster that codes for proteins involved in the production of six structurally related linear lipopeptides. Structures for each of these lipopeptides were proposed based on amino acid analysis and mass spectrometry analyses. Mutations in this cluster resulted in the loss of swarming motility of P. syringae pv. tomato DC3000 on medium containing a low percentage of agar. This phenotype is consistent with the loss of the ability to produce a lipopeptide that functions as a biosurfactant. This work gives additional evidence that mining the genomes of microorganisms followed by metabolite and phenotypic analyses leads to the identification of previously unknown secondary metabolites.

A study about Bacillus subtilis encoding an octanoyltransferase enzyme that has virtually no sequence resemblance to Escherichia coli LipB but instead has a sequence that resembles that of the E. coli lipoate ligase, LplA that scavenges lipoic acid from the environment but plays no role in de novo synthesis is reported. The identified octanoyltransferase LipM in B. subtilis which represents a new class of the PF03099 protein family suggested that octanoyl transfer activity has evolved at least twice within this superfamily.

In several Proteobacteria, LuxI-type enzymes catalyze the biosynthesis of acyl–homoserine lactones (AHL) signals using S-adenosyl–l-methionine and either cellular acyl carrier protein (ACP)-coupled fatty acids or CoA–aryl/acyl moieties as progenitors. Little is known about the molecular mechanism of signal biosynthesis, the basis for substrate specificity, or the rationale for donor specificity for any LuxI member. Here, we present several cocrystal structures of BjaI, a CoA-dependent LuxI homolog that represent views of enzyme complexes that exist along the reaction coordinate of signal synthesis. Complementary biophysical, structure–function, and kinetic analysis define the features that facilitate the unusual acyl conjugation with S-adenosylmethionine (SAM). We also identify the determinant that establishes specificity for the acyl donor and identify residues that are critical for acyl/aryl specificity. These results highlight how a prevalent scaffold has evolved to catalyze quorum signal synthesis and provide a framework for the design of small-molecule antagonists of quorum signaling. [ABSTRACT FROM AUTHOR]