Comparative transcriptional analysis of clinically relevant heat stress response in Clostridium difficile strain 630 - PubMed (original) (raw)

Comparative Study

Comparative transcriptional analysis of clinically relevant heat stress response in Clostridium difficile strain 630

Nigel G Ternan et al. PLoS One. 2012.

Abstract

Clostridium difficile is considered to be one of the most important causes of health care-associated infections worldwide. In order to understand more fully the adaptive response of the organism to stressful conditions, we examined transcriptional changes resulting from a clinically relevant heat stress (41 °C versus 37 °C) in C. difficile strain 630 and identified 341 differentially expressed genes encompassing multiple cellular functional categories. While the transcriptome was relatively resilient to the applied heat stress, we noted upregulation of classical heat shock genes including the groEL and dnaK operons in addition to other stress-responsive genes. Interestingly, the flagellin gene (fliC) was downregulated, yet genes encoding the cell-wall associated flagellar components were upregulated suggesting that while motility may be reduced, adherence--to mucus or epithelial cells--could be enhanced during infection. We also observed that a number of phage associated genes were downregulated, as were genes associated with the conjugative transposon Tn5397 including a group II intron, thus highlighting a potential decrease in retromobility during heat stress. These data suggest that maintenance of lysogeny and genome wide stabilisation of mobile elements could be a global response to heat stress in this pathogen.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1

Figure 1. Projection of differentially expressed genes on the Clostridium difficile 630 genome.

Those genes showing at least 1.5-fold change with p<0.05 were selected. From outside to inside: Ring 1, molecular clock of C. difficile strain 630 genome; Ring 2 (red), coding DNA sequences of the forward strand of the genome; Ring 3 (yellow), coding DNA sequences(CDS) of the opposite strand of the genome; Ring 4 (blue), genes upregulated at 41°C; Ring 5 (green), genes downregulated at 41°C.

Figure 2

Figure 2. Functional category annotation of differentially expressed genes (>1.5 fold, p<0.05) in the Clostridium difficile strain 630 heat stress transcriptome.

Key: Orange – up regulated; blue – down regulated.

Figure 3

Figure 3. Comparison of qRT-PCR, iTRAQ proteomics and microarray data for selected Clostridium difficile strain 630 genes.

For each individual gene, expressional fold-change values (up-hatched columns) are shown relative to the 37°C control. Corresponding iTRAQ fold-changes (gray columns) are included for comparison with microarray data (down-hatched columns) and show good correlation between the three data sets. 16S rRNA, tpi, and CD2849, whose expression did not change by more than 1.5-fold, were used as reference genes.

Figure 4

Figure 4. The flagellar motor assembly in Clostridium difficile strain 630.

Graphic is adapted from Kyoto Encyclopedia of Genes and Genomes (

http://www.genome.jp/kegg/

). Several genes involved in the flagellar assembly showed altered expression levels in response to heat-stress. Additional genes found in C. difficile (FlgN, fliA, FliT) were added following BLAST searching. There appear to be no homologues of the master regulator, FlhD/C in C. difficile strain 630. Key: Red box, down regulated >1.5 fold; blue box, up regulated >1.5 fold, black box, no statistically significant change.

Figure 5

Figure 5. Genomic context of Transposon Tn5397 in the genome of Clostridium difficile strain 630.

Key: Arrows represent direction of changes in gene expression; genes lacking an arrow are unchanged. Tn5397 ORF numbers are shown above the genes. CD0506: group II intron. tetM: tetracycline resistance determinant.

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SJ was supported by a Vice Chancellor's Research Scholarship award (2007–2010) from the University of Ulster. GMcM was supported by an Innovation Leaders award (2009) from the HSC Research and Development office (http://www.publichealth.hscni.net/directorate-public-health/hsc-research-and-development). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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