Contact-dependent suppression of Clostridioides difficile sporulation by enterococci

Sporulation by Clostridioides difficile occurs naturally in the gut among other bacteria such as enterococci, which are present in all animals. The long-term goal of this laboratory is to define the mechanistic basis of bacteria-bacteria and host interactions that modulate virulence of C. difficile. The overall objective of this proposal is to discover genetic factors involved in a potential proximity-dependent inhibition of C. difficile sporulation by enterococci. The central hypothesis is that enterococci suppress C. difficile sporulation via interactions at the cell surface. The rationale for this project is that determination of mechanisms of interaction between the two species will allow the development of treatments that limit the potential for C. difficile infection. Based on preliminary data, our overall working hypothesis for this proposal is: E. faecalis inhibits sporulation via its surface proteins when in cell-cell contact with C. difficile. To attain the overall objectives these two specific aims will be pursued: Aim 1) Identify genes in Enterococcus faecalis OG1RF that are involved in proximity-dependent inhibition of C. difficile sporulation. In these experiments, we will use an arrayed library of transposon insertion mutants to screen for genes in E. faecalis involved in suppression of sporulation. Aim 2) Define the transcriptional network of enterococci-mediated sporulation inhibition. We will develop a well calibrated transwell co-culture assay and will perform transcriptional profiling during induction of sporulation to determine genes involved in this phenomenon. The research proposed is innovative in the applicant’s opinion because it focuses specifically on interactions between two gastrointestinal pathogens and how cell contact with non-kin bacteria regulates a cell fate decision. The proposed research is significant because it will provide a context for understanding how enterococci, which commonly expand in antibiotics-treated patients, affect the balance between spore formation and vegetative toxin-producing C. difficile.