Influence of L-lactate and low glucose concentrations on the metabolism and the toxin formation of Clostridioides difficile

PLoS One. 2021 Jan 7;16(1):e0244988. doi: 10.1371/journal.pone.0244988. eCollection 2021.


The virulence of Clostridioides difficile (formerly Clostridium difficile) is mainly caused by its two toxins A and B. Their formation is significantly regulated by metabolic processes. Here we investigated the influence of various sugars (glucose, fructose, mannose, trehalose), sugar derivatives (mannitol and xylitol) and L-lactate on toxin synthesis. Fructose, mannose, trehalose, mannitol and xylitol in the growth medium resulted in an up to 2.2-fold increase of secreted toxin. Low glucose concentration of 2 g/L increased the toxin concentration 1.4-fold compared to growth without glucose, while high glucose concentrations in the growth medium (5 and 10 g/L) led to up to 6.6-fold decrease in toxin formation. Transcriptomic and metabolic investigation of the low glucose effect pointed towards an inactive CcpA and Rex regulatory system. L-lactate (500 mg/L) significantly reduced extracellular toxin formation. Transcriptome analyses of the later process revealed the induction of the lactose utilization operon encoding lactate racemase (larA), electron confurcating lactate dehydrogenase (CDIF630erm_01321) and the corresponding electron transfer flavoprotein (etfAB). Metabolome analyses revealed L-lactate consumption and the formation of pyruvate. The involved electron confurcation process might be responsible for the also observed reduction of the NAD+/NADH ratio which in turn is apparently linked to reduced toxin release from the cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Bacterial Toxins / metabolism*
  • Clostridioides difficile / drug effects
  • Clostridioides difficile / growth & development
  • Clostridioides difficile / metabolism*
  • Glucose / pharmacology*
  • Lactic Acid / pharmacology*
  • Metabolome / drug effects*
  • Sweetening Agents / pharmacology


  • Bacterial Proteins
  • Bacterial Toxins
  • Sweetening Agents
  • Lactic Acid
  • Glucose

Grants and funding

This work was funded by the Federal State of Lower Saxony, Niedersächsisches Vorab (VWZN2889/3215/3266).