title: Time-resolved amino acid uptake of Clostridium difficile 630Δerm and concomitant fermentation product and toxin formation.
abstract: BACKGROUND
  Clostridium difficile is one of the major nosocomial threats causing severe gastrointestinal infections. Compared to the well documented clinical symptoms, little is known about the processes in the bacterial cell like the regulation and activity of metabolic pathways. In this study, we present time-resolved and global data of extracellular substrates and products. In a second part, we focus on the correlation of fermentation products and substrate uptake with toxin production.
  
  
  RESULTS
  Formation of different fermentation products during growth in a comparison between the two different media in a global approach was studied using non-targeted gas chromatography-mass spectrometry (GC-MS) based analysis. During cultivation in a casamino acids medium and minimal medium, the clinical isolate C. difficile 630Δerm showed major differences in amino acid utilization: In casamino acids medium, C. difficile preferred proline, leucine and cysteine as carbon and energy sources while glutamate and lysine were not or hardly used. In contrast, proline and leucine were consumed at a significantly later stage in minimal medium. Due to the more complex substrate mixture more fermentation products were detectable in the casamino acids medium, accompanied by major changes in the ratios between oxidative and reductive Stickland products. Different glucose consumption dynamics were observed in presence of either casamino acids or the minimal set of amino acids, accompanied by major changes in butanoate formation. This was associated with a variation in both the toxin yield and a change in the ratio of toxin A to toxin B.
  
  
  CONCLUSIONS
  Since in all media compositions, more than one substrate was available as a suitable carbon source, availability of different carbon sources and their metabolic fate appears to be the key factor for toxin formation.
authors.affiliation: Technische Universität Braunschweig, Department of Bioinformatics and Biochemistry and Braunschweig Integrated Center of Systems Biology (BRICS), Langer Kamp 19b, 38106, Braunschweig, Germany. m.neumann-schaal@tu-braunschweig.de.
authors.forename: Meina
authors.initials: M
authors.lastname: Neumann-Schaal
authors.affiliation: Technische Universität Braunschweig, Department of Bioinformatics and Biochemistry and Braunschweig Integrated Center of Systems Biology (BRICS), Langer Kamp 19b, 38106, Braunschweig, Germany. ju.hofmann@tu-braunschweig.de.
authors.forename: Julia Danielle
authors.initials: JD
authors.lastname: Hofmann
authors.affiliation: Technische Universität Braunschweig, Department of Bioinformatics and Biochemistry and Braunschweig Integrated Center of Systems Biology (BRICS), Langer Kamp 19b, 38106, Braunschweig, Germany. sabine.will@tu-braunschweig.de.
authors.forename: Sabine Eva
authors.initials: SE
authors.lastname: Will
authors.affiliation: Technische Universität Braunschweig, Department of Bioinformatics and Biochemistry and Braunschweig Integrated Center of Systems Biology (BRICS), Langer Kamp 19b, 38106, Braunschweig, Germany. d.schomburg@tu-braunschweig.de.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schomburg
mesh_terms: D000596:Amino Acids / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D001427:Bacterial Toxins / Q000378:metabolism*; D016360:Clostridioides difficile / Q000254:growth & development* / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004768:Enterotoxins / Q000378:metabolism*; D005285:Fermentation; D008401:Gas Chromatography-Mass Spectrometry; D005947:Glucose / Q000378:metabolism; D064210:Secondary Metabolism
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003470:Culture Media; D004768:Enterotoxins; C017721:casamino acids; C041348:tcdA protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile; D005947:Glucose