Impacts of perR on oxygen sensitivity, gene expression, and murine infection in Clostridioides difficile 630Δerm.

Abstract

Clostridioides difficile infection (CDI), characterized by colitis and diarrhea, afflicts approximately half a million people in the United States every year, burdening both individuals and the healthcare system. C. difficile 630Δerm is an erythromycin-sensitive variant of the clinical isolate C. difficile 630 and is commonly used in the C. difficile research community due to its genetic tractability. 630Δerm possesses a point mutation in perR, an autoregulated transcriptional repressor that regulates oxidative stress resistance genes. This point mutation results in a constitutively de-repressed PerR operon in 630Δerm. To address the impacts of perR on phenotypes relevant for oxygen tolerance and relevant to a murine model of CDI, we corrected the point mutant to restore PerR function in 630Δerm (herein, 630Δerm perR WT). We demonstrate that there is no difference in growth between 630Δerm and a 630Δerm perR WT under anaerobic conditions or when exposed to concentrations of O2 that mimic those found near the surface of the colonic epithelium. However, 630Δerm perR WT is more sensitive to ambient oxygen than 630Δerm, which coincides with alterations in expression of a variety of perR-dependent and perR-independent genes. Finally, we show that 630Δerm and 630Δerm perR WT do not differ in their ability to infect and cause disease in a well-established murine model of CDI. Together, these data support the hypothesis that the perR mutation in 630Δerm arose as a result of exposure to ambient oxygen and that the perR mutation in 630Δerm is unlikely to impact CDI-relevant phenotypes in laboratory studies.