Control of key metabolic intersections in Bacillus subtilis

“…In B. subtilis, glutamate and glutamine are key amino acids involved in both the synthesis of other amino acids and the TCA cycle intermediate 2-oxoglutarate, providing a link between nitrogen and carbon metabolism (Sonenshein, 2007). However, an amino acid analysis of culture supernatants revealed that neither arginine nor glutamate/glutamine was significantly consumed by strain VPI 10463, regardless of the medium tested, whereas the BCAAs were preferentially used in PY 0 and PY 10 but conserved in PYG cultures (S. Karlsson and others, unpublished results).…”

Section: Discussionmentioning

confidence: 99%

Induction of toxins in Clostridium difficile is associated with dramatic changes of its metabolism

2008

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Certain amino acids, and cysteine in particular, promptly blocked toxin expression in Clostridium difficile strain VPI 10463 when added to late-exponential-phase peptone-yeast cultures, i.e. prior to normal induction of toxins A and B. Glucose reduced toxin yields by 80-fold, but only when supplemented at inoculation. Forty upregulated C. difficile proteins were identified during maximum toxin expression, and most of these were enzymes involved in energy exchange, e.g. succinate, CO/folate and butyrate metabolism. Transcription of tcdA (toxin operon) and folD (CO/ folate operon) was induced by 20-and 10-fold, respectively, and with strikingly similar kinetics between OD 0.8 and 1.2. The sigma factors tcdR and sigH were upregulated simultaneously with tcdA and folD (3.5-fold increase of mRNA level), whereas transcription of tcdC, codY, sigB and sigL showed little or no correlation with that of tcdA and folD. The results suggest a connection between toxin expression, alternative energy metabolism and initial sporulation events in C. difficile.

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“…However, the consensus sequences for the binding of CodY to DNA have not been completely established. 50 Finally, it has been demonstrated in B. subtilis that subtilin production is controlled by both the culture density (through a quorum-sensing mechanism) and the microbial growth phase. 45,51 Lactobacillales Lactic acid bacteria display numerous antimicrobial activities; among them, bacteriocins are especially important because of their use as food preservatives.…”

Section: Bacillalesmentioning

confidence: 99%