The small acid-soluble proteins of Clostridioides difficile are important for UV resistance and serve as a check point for sporulation.

Hailee N Nerber,Joseph A Sorg,Bruce A Mcclane

doi:10.1371/journal.ppat.1009516

Abstract

Clostridioides difficile is a nosocomial pathogen which causes severe diarrhea and colonic inflammation. C. difficile causes disease in susceptible patients when endospores germinate into the toxin-producing vegetative form. The action of these toxins results in diarrhea and the spread of spores into the hospital and healthcare environments. Thus, the destruction of spores is imperative to prevent disease transmission between patients. However, spores are resilient and survive extreme temperatures, chemical exposure, and UV treatment. This makes their elimination from the environment difficult and perpetuates their spread between patients. In the model spore-forming organism, Bacillus subtilis, the small acid-soluble proteins (SASPs) contribute to these resistances. The SASPs are a family of small proteins found in all endospore-forming organisms, C. difficile included. Although these proteins have high sequence similarity between organisms, the role(s) of the proteins differ. Here, we investigated the role of the main α/β SASPs, SspA and SspB, and two annotated putative SASPs, CDR20291_1130 and CDR20291_3080, in protecting C. difficile spores from environmental insults. We found that SspA is necessary for conferring spore UV resistance, SspB minorly contributes, and the annotated putative SASPs do not contribute to UV resistance. In addition, the SASPs minorly contribute to the resistance of nitrous acid. Surprisingly, the combined deletion of sspA and sspB prevented spore formation. Overall, our data indicate that UV resistance of C. difficile spores is dependent on SspA and that SspA and SspB regulate/serve as a checkpoint for spore formation, a previously unreported function of SASPs.

Highlights

Clostridioides difficile is the leading cause of antibiotic associated diarrhea with ~224,000 annual infections in the United States [1,2,3]
We found that C. difficile SspA is the major contributor to UV resistance of the spores and that SspB is minorly involved in UV resistance
In addition to providing UV resistance to spores, the major C. difficile small acid-soluble proteins (SASPs) are involved in spore formation

Summary

Introduction

Clostridioides difficile is the leading cause of antibiotic associated diarrhea with ~224,000 annual infections in the United States [1,2,3]. Upon inoculation into a susceptible host, C. difficile spores germinate to the toxin-producing vegetative form [4]. These toxins lead to the disruption of the colonic epithelium and the common symptoms of disease (e.g., diarrhea and colitis) [4]. Vancomycin and fidaxomicin are the recommended treatments for C. difficile infection [4,6]. While these antibiotics treat the infection by targeting the actively-growing vegetative cells, the spore form is resistant to antibiotics [5,7]. In contrast to the anaerobic nature of the C. difficile vegetative cell, spores can survive the oxygen-rich environment outside of a host, and are considered the transmissible form [5,8,9]

Methods

Results

Conclusion