Detection of the formyl radical by EPR spin-trapping and mass spectrometry.

For the first time we here present the unambiguous identification of the formyl radical ((CHO)-C-center dot) by EPR (Electron Paramagnetic Resonance) spectroscopy and mass spectrometry (MS) using DMPO (5,5-dimethyl-1-pyrroline N-oxide) as spin trap at ambient temperature without using any catalyst(s). The (CHO)-C-center dot was continuously generated by UV photolysis in closed anoxic environment from pure formaldehyde (HCHO) in aqueous solution. The isotropic hyperfine structure constants of (CHO)-C-center dot were determined as a(N)= 15.72 G and a(H) = 21.27 G. The signals were deconvoluted and split by simulation in their single adduct components: DMPO-CHO, DMPO-H and DMPO-OH. We verified our results at first using MNP (2-methyl-2-nitroso-propane) as spin trap with known literature data and then mass spectrometry. Similarly the MNP adduct components MNP-CHO, MNP-H as well as its own adduct, the MNP-2-methyl-2-propyl (MNP-MP) were deconvoluted. Due to the low signal intensities, we had to accumulate single measurements for both spin traps. Using MS we got the exact mass of the reduced (CHO)-C-center dot adduct independently confirming the result of EPR detection of formyl radical

DIAMetAlyzer allows automated false-discovery rate-controlled analysis for data-independent acquisition in metabolomics.

The extraction of meaningful biological knowledge from high-throughput mass spectrometry data relies on limiting false discoveries to a manageable amount. For targeted approaches in metabolomics a main challenge is the detection of false positive metabolic features in the low signal-to-noise ranges of data-independent acquisition results and their filtering. Another factor is that the creation of assay libraries for data-independent acquisition analysis and the processing of extracted ion chromatograms have not been automated in metabolomics. Here we present a fully automated open-source workflow for high-throughput metabolomics that combines data-dependent and data-independent acquisition for library generation, analysis, and statistical validation, with rigorous control of the false-discovery rate while matching manual analysis regarding quantification accuracy. Using an experimentally specific data-dependent acquisition library based on reference substances allows for accurate identification of compounds and markers from data-independent acquisition data in low concentrations, facilitating biomarker quantification

Pseudomonas putida as saviour for troubled Synechococcus elongatus in a synthetic co-culture – interaction studies based on a multi-OMICs approach

In their natural habitats, microbes rarely exist in isolation; instead, they thrive in consortia, where various interactions occur. In this study, a defined synthetic co-culture of the cyanobacterium S. elongatus cscB, which supplies sucrose to the heterotrophic P. putida cscRABY, is investigated to identify potential interactions. Initial experiments reveal a remarkable growth-promoting effect of the heterotrophic partner on the cyanobacterium, resulting in an up to 80% increase in the growth rate and enhanced photosynthetic capacity. Vice versa, the presence of the cyanobacterium has a neutral effect on P. putida cscRABY, highlighting the resilience of pseudomonads against stress and their potential as co-culture partners. Next, a suitable reference process reinforcing the growth-promoting effect is established in a parallel photobioreactor system, which sets the basis for the analysis of the co-culture at the transcriptome, proteome, and metabolome levels. In addition to several moderate changes, including alterations in the metabolism and stress response in both microbes, this comprehensive multi-OMICs approach strongly hints towards the exchange of further molecules beyond the unidirectional feeding with sucrose. Taken together, these findings provide valuable insights into the complex dynamics between both co-culture partners, indicating multi-level interactions, which can be employed for further streamlining of the co-cultivation system

Genetic manipulation of the <em>Fusarium fujikuroi </em>fusarin gene cluster yields insight into the complex regulation and fusarin biosynthetic pathway.

In this work, the biosynthesis and regulation of the polyketide synthase/nonribosomal peptide synthetase (PKS/NRPS)-derived mutagenic mycotoxin fusarin C was studied in the fungus Fusarium fujikuroi. The fusarin gene cluster consists of nine genes (fus1-fus9) that are coexpressed under high-nitrogen and acidic pH conditions. Chromatin immunoprecipitation revealed a correlation between high expression and enrichment of activating H3K9-acetylation marks under inducing conditions. We provide evidence that only four genes are sufficient for the biosynthesis. The combination of genetic engineering with nuclear magnetic resonance and mass-spectrometry-based structure elucidation allowed the discovery of the putative fusarin biosynthetic pathway. Surprisingly, we indicate that PKS/NRPS releases its product with an open ring structure, probably as an alcohol. Our data indicate that 2-pyrrolidone ring closure, oxidation at C-20, and, finally, methylation at C-20 are catalyzed by Fus2, Fus8, and Fus9, respectively

Ring Trial on Quantitative Assessment of Bile Acids Reveals a Method- and Analyte-Specific Accuracy and Reproducibility

Bile acids are a key mediator of the molecular microbiome-host interaction, and various mass spectrometry-based assays have been developed in the recent decade to quantify a wide range of bile acids. We compare existing methodologies to harmonize them. Methodology for absolute quantification of bile acids from six laboratories in Europe were compared for the quantification of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) and conjugated products glycocholic acid (GCA) and taurocholic acid (TCA). For the bacterially modified secondary bile acids, the quantification of deoxycholic acid (DCA) and lithocholic acid (LCA) was compared. For the murine bile acids, we used the primary muricholic acids (alpha-MCA and, beta-MCA) and the intestinally produced secondary bile acid muricholic (omega-MCA). The standards were spiked into methanol:water (1:1) mix as well as in human and murine serum at either low concentration range (150-3000 nM) or high concentration range (1500-40,000 nM). The precision was better for higher concentrations. Measurements for the hydrophobic unconjugated bile acids LCA and omega-MCA were the most challenging. The quality assessments were generally very similar, and the comprehensive analyses demonstrated that data from chosen locations can be used for comparisons between studies

Ring Trial on Quantitative Assessment of Bile Acids Reveals a Method- and Analyte-Specific Accuracy and Reproducibility

Bile acids are a key mediator of the molecular microbiome-host interaction, and various mass spectrometry-based assays have been developed in the recent decade to quantify a wide range of bile acids. We compare existing methodologies to harmonize them. Methodology for absolute quantification of bile acids from six laboratories in Europe were compared for the quantification of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) and conjugated products glycocholic acid (GCA) and taurocholic acid (TCA). For the bacterially modified secondary bile acids, the quantification of deoxycholic acid (DCA) and lithocholic acid (LCA) was compared. For the murine bile acids, we used the primary muricholic acids (alpha-MCA and, beta-MCA) and the intestinally produced secondary bile acid muricholic (omega-MCA). The standards were spiked into methanol:water (1:1) mix as well as in human and murine serum at either low concentration range (150-3000 nM) or high concentration range (1500-40,000 nM). The precision was better for higher concentrations. Measurements for the hydrophobic unconjugated bile acids LCA and omega-MCA were the most challenging. The quality assessments were generally very similar, and the comprehensive analyses demonstrated that data from chosen locations can be used for comparisons between studies

Skeletal muscle hypertrophy rewires glucose metabolism: An experimental investigation and systematic review

Background: Proliferating cancer cells shift their metabolism towards glycolysis, even in the presence of oxygen, to especially generate glycolytic intermediates as substrates for anabolic reactions. We hypothesize that a similar metabolic remodelling occurs during skeletal muscle hypertrophy. Methods: We used mass spectrometry in hypertrophying C2C12 myotubes in vitro and plantaris mouse muscle in vivo and assessed metabolomic changes and the incorporation of the [U-13C6]glucose tracer. We performed enzyme inhibition of the key serine synthesis pathway enzyme phosphoglycerate dehydrogenase (Phgdh) for further mechanistic analysis and conducted a systematic review to align any changes in metabolomics during muscle growth with published findings. Finally, the UK Biobank was used to link the findings to population level. Results: The metabolomics analysis in myotubes revealed insulin-like growth factor-1 (IGF-1)-induced altered metabolite concentrations in anabolic pathways such as pentose phosphate (ribose-5-phosphate/ribulose-5-phosphate: +40%; P = 0.01) and serine synthesis pathway (serine: −36.8%; P = 0.009). Like the hypertrophy stimulation with IGF-1 in myotubes in vitro, the concentration of the dipeptide l-carnosine was decreased by 26.6% (P = 0.001) during skeletal muscle growth in vivo. However, phosphorylated sugar (glucose-6-phosphate, fructose-6-phosphate or glucose-1-phosphate) decreased by 32.2% (P = 0.004) in the overloaded muscle in vivo while increasing in the IGF-1-stimulated myotubes in vitro. The systematic review revealed that 10 metabolites linked to muscle hypertrophy were directly associated with glycolysis and its interconnected anabolic pathways. We demonstrated that labelled carbon from [U-13C6]glucose is increasingly incorporated by ~13% (P = 0.001) into the non-essential amino acids in hypertrophying myotubes, which is accompanied by an increased depletion of media serine (P = 0.006). The inhibition of Phgdh suppressed muscle protein synthesis in growing myotubes by 58.1% (P < 0.001), highlighting the importance of the serine synthesis pathway for maintaining muscle size. Utilizing data from the UK Biobank (n = 450 243), we then discerned genetic variations linked to the serine synthesis pathway (PHGDH and PSPH) and to its downstream enzyme (SHMT1), revealing their association with appendicular lean mass in humans (P < 5.0e-8). Conclusions: Understanding the mechanisms that regulate skeletal muscle mass will help in developing effective treatments for muscle weakness. Our results provide evidence for the metabolic rewiring of glycolytic intermediates into anabolic pathways during muscle growth, such as in serine synthesis