An investigation of trehalose metabolism by the enteropathogen, Clostridium difficile

An exception was TreX, whose functional role was thought inconclusive as the protein lacked a number of expected conserved trehalase motifs. Using representative strains from each of the five toxigenic clades, hypervirulent strains were then shown to be capable of growing on trehalose at low (10 mM) or high (50 mM) concentrations, whilst non-hypervirulent strains could not. Transcriptional profiling of the treR, treA, treA2, ptsT, treX and treR2 trehalose metabolism genes then showed further inter-strain differences at the gene expression level.

Interestingly whilst an increase in expression levels was found in the non-hypervirulent strains at the low trehalose concentration this was evidently not sufficient to translate into observable growth. Finally, in the hypervirulent R20291 and M120 strains, the presence of trehalose was found to decrease expression levels of the tcdA and tcdB toxin genes and the early-sporulation sigma factor gene, sigE raising the possibility that trehalose may actually limit a number of key processes associated with pathogenesis. <br><br>For the first time it was then shown that the TreR regulator protein within the C. difficile genome displays DNA-binding activity to both the treR and treA genes.

Additionally, it was confirmed experimentally for the first time that the presence of trehalose-6-phosphate acts as an effector leading to increased binding of the TreR protein from R20291 to its target DNA, thus suggesting a potential role as a transcriptional activator. Finally, RNA-sequencing analysis of the hypervirulent R20291 strain provided an insight into the metabolic rewiring that C. difficile carries out during growth on an alternative carbon source.

Of importance and requiring further investigation, it revealed for the first time in C. difficile the induction of an alternative trehalose metabolism pathway, previously elucidated in Lactococcus lactis, whose trehalose metabolism relies on a similar pathway.