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

2021 ◽  
Vol 9 ◽  
Author(s):  
Tanya Clements ◽  
Marina Rautenbach ◽  
Thando Ndlovu ◽  
Sehaam Khan ◽  
Wesaal Khan
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Fatty Acid ◽  
Secondary Metabolites ◽  
Tandem Mass Spectrometry ◽  
Metabolic Profiles ◽  
Tandem Mass ◽  
Molecular Networking ◽  
Rp Hplc ◽  
Open Ring

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.

202 Proteomic, metabolomic and fatty acid composition in lactating and non-lactating mares’ uterine fluids

2020 ◽  
Vol 32 (2) ◽  
pp. 229
Author(s):  
E. Derisoud ◽  
A. Hankele ◽  
L. Jouneau ◽  
C. Dubois ◽  
D. Rousseau-Ralliard ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Fatty Acid Composition ◽  
Liquid Chromatography ◽  
Fatty Acid ◽  
Tandem Mass Spectrometry ◽  
Acid Composition ◽  
Enrichment Score ◽  
Tandem Mass ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass

In the equine industry, horse breeders aim to produce one foal per mare per year. Thus, mares are bred while nursing. In high-yielding dairy cattle, concurrent lactation and conception may affect embryo quality, but effects on uterine fluid (UF) quality are unknown. No data are available in horses. The aim of our study was to analyse the effect of nursing on protein, metabolite and fatty acid (FA) compositions of UF at ~7.5 days post-ovulation. Anglo-Arab mares (multiparous (2.7±0.9 foals), 10.8±2.5 years old) that were either nursing (N; 105±12 days of lactation) or barren (B) were inseminated with the semen of the same stallion at induction of ovulation with human chorionic gonadotrophin. Ovulation was confirmed by ultrasound within 48h. At 7.4±0.7 days post-ovulation, UF was collected with a human tampon that was left for 10min in the uterus before embryo collection. Only mares for which no embryo was collected were selected (n=5 in both groups). Trypsin digestion followed by liquid chromatography-tandem mass spectrometry analysis was used for proteomic analysis, with subsequent characterisation with the PANTHER platform using an overrepresentation test (Fisher's exact type with false discovery rate correction) with the PANTHER pathway database. An untargeted approach based on liquid chromatography-tandem mass spectrometry was performed for metabolomics (normalisation to 50µg of protein), and data were analysed with the MS Peaks to Pathways tool of the MetaboAnalyst platform, using both the GSEA and mummichog algorithms (cut-off=0.05). Fatty acid composition (% of total FA) was analysed using gas chromatography. Differences between groups were analysed using a linear model with permutation using R software with the pgirmess package (P=0.05 for significance). Altogether, 2706 proteins with at least two peptides were identified in mares’ UF, with 164 being differentially expressed. Ubiquitin proteasome, involved in embryo-endometrium interactions, was the most enriched pathway in N mares (fold enrichment=15.12; P<0.0001). For metabolomics, ubiquinone biosynthesis [MetaFishNet, P=0.02; NES (Enrichment Score for the variable)/(mean of all Enrichment Score in all permutations in the dataset)=1.84] was enriched in N mares. N-Glycans, mainly guanosine diphosphate mannose (Kyoto Encyclopedia of Genes and Genomes, P=0.04; NES=−1.33) and leukotriene biosynthesis (Biocyc; P=0.006; NES=−1.31), were enriched in B mares with differentially expressed leukotrienes C4/D4. The proportion of saturated FA was higher in N vs. B mares (38.4±3.6% vs. 33.2±3.6%; P=0.03), probably due to increased palmitic (P=0.08) and stearic (P=0.08) acid proportions. In conclusion, pathways involved in uterine receptivity and inflammation seem to be enriched in B mares. Fatty acids that are readily available in the diet were more present in N mares, possibly because more elaborate FA are exported to the mammary gland for milk production. Nursing could thus modify the inflammatory response in the uterine environment at ~7.5 days post-ovulation and could affect reproductive efficiency in horses.

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