The LexA regulated genes of the Clostridium difficile.

Beata Walter (1) , Maja Rupnik (1, 2, 3) , Vesna Hodnik (4) , Gregor Anderluh (4, 5) , Bruno Dupuy (6) , Nejc Paulič (4) , Darja Žgur-Bertok (4) , Matej Butala (4)

1 Institute of Public Health Maribor
2 Faculty of Medicine
3 Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins
4 Biotechnical Faculty
5 KI - National Institute of Chemistry [Llubljana]
6 PBA (U-Pasteur_6) - Pathogénèse des Bactéries Anaérobies / Pathogenesis of Bacterial Anaerobes

BACKGROUND: The SOS response including two main proteins LexA and RecA, maintains the integrity of bacterial genomes after DNA damage due to metabolic or environmental assaults. Additionally, derepression of LexA-regulated genes can result in mutations, genetic exchange and expression of virulence factors. Here we describe the first comprehensive description of the in silico LexA regulon in Clostridium difficile, an important human pathogen. RESULTS: We grouped thirty C. difficile strains from different ribotypes and toxinotypes into three clusters according to lexA gene/protein variability. We applied in silico analysis coupled to surface plasmon resonance spectroscopy (SPR) and determined 16 LexA binding sites in C. difficile. Our data indicate that strains within the cluster, as defined by LexA variability, harbour several specific LexA regulon genes. In addition to core SOS genes: lexA, recA, ruvCA and uvrBA, we identified a LexA binding site on the pathogenicity locus (PaLoc) and in the putative promoter region of several genes involved in housekeeping, sporulation and antibiotic resistance. CONCLUSIONS: Results presented here suggest that in C. difficile LexA is not merely a regulator of the DNA damage response genes but also controls the expression of dozen genes involved in various other biological functions. Our in vitro results indicate that in C. difficile inactivation of LexA repressor depends on repressor's dissociation from the operators. We report that the repressor's dissociation rates from operators differentiate, thus the determined LexA-DNA dissociation constants imply on the timing of SOS gene expression in C. difficile.

Mots clés: Clostridium difficile; Antibiotic resistance; Toxin regulation; SOS system; Surface plasmon resonance; LexA repressor

Domaines: Microbiologie et Parasitologie

Beata Walter, Maja Rupnik, Vesna Hodnik, Gregor Anderluh, Bruno Dupuy, et al.. The LexA regulated genes of the Clostridium difficile.. BMC Microbiology, 2014, 14 (1), pp.88. ⟨10.1186/1471-2180-14-88⟩. ⟨pasteur-00976526⟩