Clostridioides difficile spore: coat assembly and formation

Abstract

Clostridioides difficile (C. difficile) is a Gram-positive, spore-forming, toxin-producing, obligate anaerobic bacterium. C. difficile infection (CDI) is the leading cause of healthcare-associated infective diarrhoea. The infection is mediated by the spore, a metabolically inactive form of C. difficile. The spore coat acts as a physical barrier to defend against chemical insults from hosts and natural environments. The composition of spore coat has already been revealed; therefore, the interactive networks of spore coat proteins and the dynamic process of coat assembly are the keys to design strategies to control and cure CDI. This review gives a brief discussion of the signal processing and transcriptional regulation of C. difficile sporulation initiation. Following the discussion, the spore formation is also introduced. Finally, this review mainly focuses on the spore coat assembly, a poorly understood process in C. difficile, and important proteins that have been studied.

Keywords: Clostridioides difficile; coat assembly; morphogenetic protein; spore formation; sporulation.

Figure 1.

Sporulation of Clostridioides difficile. This figure summarizes the sporulation initiation and spore formation described in this review. Red arrows indicate transcriptional activation. Red cross arrows indicate transcriptional inhibition. Red bold arrows indicate post-translational regulations. Question marks indicate suggestive but unconfirmed mechanisms.

Figure 2.

Coat assembly of Clostridioides difficile. This figure summarizes the coat assembly process described in this review. The coloured boxes on the left indicate SigE and SigK regulon. The box on the top right shows a proposed model of the spore coat assembly of the first stage, while the box on the bottom right shows the second stage. Question marks indicate unknown/unconfirmed proteins.