A Metabolomics and Molecular Networking Approach to Elucidate the Structures of Secondary Metabolites Produced by Serratia marcescens Strains

Abstract

An integrated approach that combines reverse-phase high-performance liquid chromatography (RP-HPLC), electrospray ionization mass spectrometry, untargeted ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MSE) and molecular networking (using the Global Natural Products Social molecular network platform) was used to elucidate the metabolic profiles and chemical structures of the secondary metabolites produced by pigmented (P1) and non-pigmented (NP1) Serratia marcescens (S. marcescens) strains. Tandem mass spectrometry-based molecular networking guided the structural elucidation of 18 compounds for the P1 strain (including 6 serratamolides, 10 glucosamine derivatives, prodigiosin and serratiochelin A) and 15 compounds for the NP1 strain (including 8 serratamolides, 6 glucosamine derivatives and serratiochelin A) using the MSE fragmentation profiles. The serratamolide homologues were comprised of a peptide moiety of two L-serine residues (cyclic or open-ring) linked to two fatty acid chains (lengths of C10, C12, or C12:1). Moreover, the putative structure of a novel open-ring serratamolide homologue was described. The glucosamine derivative homologues (i.e., N-butylglucosamine ester derivatives) consisted of four residues, including glucose/hexose, valine, a fatty acid chain (lengths of C13 – C17 and varying from saturated to unsaturated) and butyric acid. The putative structures of seven novel glucosamine derivative homologues and one glucosamine derivative congener (containing an oxo-hexanoic acid residue instead of a butyric acid residue) were described. Moreover, seven fractions collected during RP-HPLC, with major molecular ions corresponding to prodigiosin, serratamolides (A, B, and C), and glucosamine derivatives (A, C, and E), displayed antimicrobial activity against a clinical Enterococcus faecalis S1 strain using the disc diffusion assay. The minimum inhibitory and bactericidal concentration assays however, revealed that prodigiosin exhibited the greatest antimicrobial potency, followed by glucosamine derivative A and then the serratamolides (A, B, and C). These results provide crucial insight into the secondary metabolic profiles of pigmented and non-pigmented S. marcescens strains and confirms that S. marcescens strains are a promising natural source of novel antimicrobial metabolites.

Prodigiosin inhibits bacterial growth and virulence factors as a potential physiological response to interspecies competition

“…The column temperature was maintained at 40°C and separation of the extract was facilitated with milliQ water containing 0.1% ( v/v ) formic acid as solvent A and acetonitrile containing 0.1% ( v/v ) formic acid as solvent B. The flow rate was 0.3 mL per minute (mL/min) with gradient developed as follows: 60% of solvent A from 0 to 0.5 min for loading, linear gradient from 20 to 80% (solvent B) from 0.5 to 14 min and 0–100% (solvent B) from 14 to 15 min [ 31 ]. The elutes were then subjected to a capillary voltage of 3.5 kV, source temperature of 200°C, nebuliser pressure of 35 psi, desolvation nitrogen gas at flow rate of 11 L/min, desolvation temperature at 350°C and collision energy at 0 eV.…”

Deep-Sea Sediments from the Southern Gulf of Mexico Harbor a Wide Diversity of PKS I Genes

“…Prodigiosin is one of the secondary metabolites that are encoded in the metagenomes analyzed in this study. This red tripyrrole pigment, belonging to the prodiginines family, is produced by several bacterial genera, such as Serratia , Hahella , Streptomyces , Zooshikella , Vibrio , and Pseudomonas [ 45 ], and is known to have immunosuppressive, antifungal, antiviral, antimicrobial, anti-malarial, and anti-proliferative properties [ 46 , 47 ]. Genes encoding monoterpenoids were also detected in our data.…”

Metabolomics and Genomics Approach for the Discovery of Serrawettin W2 Lipopeptides from Serratia marcescens NP2

“…The production of the secondary metabolites by S. marcescens NP2 was performed as described by Clements et al in a 2 L baffled flask containing 500 mL peptone glycerol (PG, pH 7.2 ± 0.2) broth, in triplicate, for two independent production schemes . The baffled flasks were inoculated and incubated on an orbital shaker (MRCLAB, London, United Kingdom) at 30 °C for 120 h at 120 rpm.…”

“…Lipopeptides represent a class of low-molecular weight compounds composed of a hydrophilic peptide attached to a hydrophobic lipid or fatty acid residue . The lipopeptides produced by the Serratia species include serrawettins W1 (initially referred to as serratamolide A), W2, and W3, as well as the recently discovered stephensiolides. , Serrawettin W1 and various homologues of this cyclic lipopeptide have been identified by extensive chemical characterization, indicating that this lipopeptide is composed of two l -Ser amino acid residues linked to two β-hydroxy fatty acid residues. − Serrawettin W2 was first isolated in 1986 and was identified as a cyclic lipopeptide comprised of five amino acid residues ( d -Leu/Ile- l -Ser- l -Thr- d -Phe- l -Ile/Leu), connected to a β-hydroxydecanoic acid moiety, produced by the Serratia marcescens NS 25 strain. , Analogues of serrawettin W2 have been isolated from cultures of S. marcescens and S.…”