Genome-Wide Transcriptional Profiling of Clostridium perfringens SM101 during Sporulation Extends the Core of Putative Sporulation Genes and Genes Determining Spore Properties and Germination Characteristics.

Yinghua Xiao,Sacha A F T Van Hijum,Marjon H J Wells-Bennik,Tjakko Abee

doi:10.1371/journal.pone.0127036

Abstract

The formation of bacterial spores is a highly regulated process and the ultimate properties of the spores are determined during sporulation and subsequent maturation. A wide variety of genes that are expressed during sporulation determine spore properties such as resistance to heat and other adverse environmental conditions, dormancy and germination responses. In this study we characterized the sporulation phases of C. perfringens enterotoxic strain SM101 based on morphological characteristics, biomass accumulation (OD600), the total viable counts of cells plus spores, the viable count of heat resistant spores alone, the pH of the supernatant, enterotoxin production and dipicolinic acid accumulation. Subsequently, whole-genome expression profiling during key phases of the sporulation process was performed using DNA microarrays, and genes were clustered based on their time-course expression profiles during sporulation. The majority of previously characterized C. perfringens germination genes showed upregulated expression profiles in time during sporulation and belonged to two main clusters of genes. These clusters with up-regulated genes contained a large number of C. perfringens genes which are homologs of Bacillus genes with roles in sporulation and germination; this study therefore suggests that those homologs are functional in C. perfringens. A comprehensive homology search revealed that approximately half of the upregulated genes in the two clusters are conserved within a broad range of sporeforming Firmicutes. Another 30% of upregulated genes in the two clusters were found only in Clostridium species, while the remaining 20% appeared to be specific for C. perfringens. These newly identified genes may add to the repertoire of genes with roles in sporulation and determining spore properties including germination behavior. Their exact roles remain to be elucidated in future studies.

Highlights

Clostridium perfringens is the causative agent of various animal and human diseases including clinical gas gangrene and foodborne diarrhea [1]
The succession of events during growth and the sporulation process of C. perfringens SM101 was characterized in modified Duncan-Strong (mDS) medium in detail
Representative time points for different phases throughout this process were selected and whole-genome expression profiling was performed throughout sporulation. This confirmed expression of known sporulation genes, of genes that had been predicted to play a role in sporulation in other studies, and of genes that have so far not been associated with sporulation, but which may play a role in sporulation and potentially determine spore properties, including spore germination behavior

Summary

Introduction

Clostridium perfringens is the causative agent of various animal and human diseases including clinical gas gangrene and foodborne diarrhea [1]. Its dormant endospores are highly resistant to environmental insults, such as heat, draught, sanitizing agents, and preservatives. This allows for the widespread occurrence of this anaerobe in food materials and in the intestinal tract of humans and animals [2]. Noteworthy is that certain C. perfringens strains produce and release diarrhea-causing enterotoxin (CPE) during sporulation. The production of this toxin is strictly associated with spore formation and mother cell lysis in the gastrointestinal tract [4]

Methods

Results

Conclusion