Clostridioides difficileLuxS mediates inter-bacterial interactions within biofilms

Abstract

AbstractThe anaerobic gut pathogen,Clostridioides difficile, forms adherent biofilms that may play an important role in recurrentC. difficileinfections. The mechanisms underlyingC. difficilecommunity formation and inter-bacterial interactions are nevertheless poorly understood.C. difficileproduces AI-2, a quorum sensing molecule that modulates biofilm formation across many bacterial species. We found that a strain defective in LuxS, the enzyme that mediates AI-2 production, is defective in biofilm developmentin vitro. Transcriptomic analyses of biofilms formed by wild type (WT) andluxSmutant (luxS) strains revealed a downregulation of prophage loci in theluxSmutant biofilms compared to the WT. Detection of phages and eDNA within biofilms may suggest that DNA release by phage-mediated cell lysis contributes toC. difficilebiofilm formation. In order to understand if LuxS mediatesC. difficilecrosstalk with other gut species,C. difficileinteractions with a common gut bacterium,Bacteroides fragilis, were studied. We demonstrate thatC. difficilegrowth is significantly reduced when co-cultured withB. fragilisin mixed biofilms. Interestingly, the absence ofC. difficileLuxS alleviates theB. fragilismediated growth inhibition. Dual species RNA-sequencing analyses from single and mixed biofilms revealed differential modulation of distinct metabolic pathways forC. difficileWT,luxSandB. fragilisupon co-culture, indicating that AI-2 may be involved in induction of selective metabolic responses inB. fragilis. Overall, our data suggest thatC. difficileLuxS/AI-2 utilises different mechanisms to mediate formation of single and mixed species communities.