Abstract
Clostridioides difficile is a Gram-positive anaerobic intestinal pathogenic bacterium and the causative agent of antibiotic-associated diarrhea. C. difficile spore is a dormant state which acts as a vehicle of transmission and infection. In C. difficile spores, the outermost exosporium layer is the first barrier of interaction with the host and should carry spore ligands involved in spore-host interactions. C. difficile forms two types of spores (i.e., thin and thick exosporium layers). In this communication, we contribute to understand several biological aspects of these two exosporium morphotypes. By transmission electron microscopy, we demonstrate that both exosporium morphotypes appear simultaneously during sporulation and that spore-coat laminations are formed under anaerobic conditions. Nycodenz density-gradient allows enrichment of spores with a thick-exosporium layer morphotype and presence of polar appendage. Using translational fluorescent fusions with exosporium proteins BclA3, CdeA, CdeC, and CdeM as well as with several spore coat proteins, we observed that expression intensity and distribution of SNAP-translational fusions in R20291 strain is highly heterogeneous. Electron micrographs demonstrate that multicopy expression of CdeC, but not CdeM, SNAP translational fusion, increases the abundance of the thick exosporium morphotype. Collectively, these results raise further questions on how these distinctive exosporium morphotypes are made during spore formation.
Highlights
Clostridioides difficile is the leading cause of nosocomial antibiotic-associated diarrhea (Rupnik et al, 2009; Martin et al, 2016)
The outermost layer of C. difficile spores is thought to act as the site of contact during the first stages of infection
Most epidemically relevant strains have an exosporium with hair-like projections that builds on top of a thin layer of electron dense material surrounding the spore coat; alternatively, these projections may build on top of a thicker layer of electron dense material that surrounds the spore coats (PizarroGuajardo et al, 2016b)
Summary
Clostridioides difficile is the leading cause of nosocomial antibiotic-associated diarrhea (Rupnik et al, 2009; Martin et al, 2016). The main factor involved in the recurrence of CDI is the formation of metabolically dormant spores during the infection (Deakin et al, 2012). These newly formed spores are essential for the persistence of C. difficile in the host and the transmission of the disease to a new Clostridium difficile Spore Morphotypes During Sporulation susceptible host (Deakin et al, 2012). Sporulation is initiated by an asymmetric cell division that leads to the formation of the mother cell and the incipient forespore (Fimlaid et al, 2013). Sporulation in C. difficile is asynchronous, at a given time, multiple stages of development can be found (Pereira et al, 2013), hampering the study of synchronized cultures
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