Project description:Clostridioides difficile (formerly Clostridium difficile) colonizes the gastrointestinal tract following disruption of the microbiota and can initiate a spectrum of clinical manifestations ranging from asymptomatic to life-threatening colitis. Following antibiotic treatment, luminal oxygen concentrations increase, exposing gut microbes to potentially toxic reactive oxygen species (ROS). Though typically regarded as a strict anaerobe, C. difficile can grow at low oxygen concentrations. How the bacterium adapts to a microaerobic environment and whether those responses to oxygen are conserved amongst strains is not entirely understood. Here, two C. difficile strains (630 and CD196) were cultured in 1.5% oxygen and the transcriptional response was evaluated via RNA-sequencing. During growth in a microaerobic environment, several genes predicted to protect against oxidative stress were upregulated, including ruberythrins and rubredoxins. Genes involved in metal homeostasis were positively correlated with increasing oxygen levels and were also amongst the most differentially transcribed. These included ferrous iron transporters (feo), a zinc transporter (zupT), and predicted siderophore transporters. To directly compare the transcriptional landscape between C. difficile strains, a ‘consensus-genome’ was generated. On the basis of the identified conserved genes, basal transcriptional differences as well as variations in the response to oxygen were evaluated. While several responses were similar between the strains, there were significant differences in the abundance of transcripts for amino acid and carbohydrate metabolism. Furthermore, homologous metal homeostasis genes were similarly transcribed, but the intracellular metal concentrations significantly varied both in an oxygen-dependent and independent manner. Overall, these results indicate that C. difficile adapts to grow in a low oxygen environment through transcriptional changes, though the specific strategy employed varies between strains.
Project description:Metabolomic and transcriptomic analysis of changes in the exponential and stationary phase of Clostridioides difficile after cultivation in casamino acids medium (reference) and supplemented with L-lactate and the connection to toxin production.
Project description:Purpose: to determine the differentially expressed genes in the phase-variable rough and smooth colony isolates of C. difficile Methods: C. difficile R20291 was grown on BHIS agar to obtain distinct colonies. Individual rough and smooth colonies were chosen for propagation on BHIS-agar for 24 hours as described in Garrett, et al., PLoS Biology, 2019. Growth was collected from n = 2 biological replicates. RNA was purified using TriSure and chloroform, beadbeating, and isopropanol/ethanol precipitation. Quality was verified with Bioanalyzer Assay. Samples were submitted to Genewiz for depletion of rRNA using the TruSeq RiboZero Gold Kit, library preparation, and single-end sequencing on the Illumina HiSeq 2500 platform. RNA sequencing analysis was done using CLC Genomic Workbench v20. Reads were mapped to C. difficile R20291 genome using the software's default menalties for mismatch, deletion, and insertion differences from the reference genome. Transcript reads were normalized as RPKM. Results: 88 genes were differentially expressed between bacteria from rough versus smooth colonies, with equal to or greater than a 2-fold change and p < 0.05 with FDR correction.