Coxiella burnetii transcriptional analysis reveals serendipity clusters of regulation in intracellular bacteria - PubMed (original) (raw)
Coxiella burnetii transcriptional analysis reveals serendipity clusters of regulation in intracellular bacteria
Quentin Leroy et al. PLoS One. 2010.
Abstract
Coxiella burnetii, the causative agent of the zoonotic disease Q fever, is mainly transmitted to humans through an aerosol route. A spore-like form allows C. burnetii to resist different environmental conditions. Because of this, analysis of the survival strategies used by this bacterium to adapt to new environmental conditions is critical for our understanding of C. burnetii pathogenicity. Here, we report the early transcriptional response of C. burnetii under temperature stresses. Our data show that C. burnetii exhibited minor changes in gene regulation under short exposure to heat or cold shock. While small differences were observed, C. burnetii seemed to respond similarly to cold and heat shock. The expression profiles obtained using microarrays produced in-house were confirmed by quantitative RT-PCR. Under temperature stresses, 190 genes were differentially expressed in at least one condition, with a fold change of up to 4. Globally, the differentially expressed genes in C. burnetii were associated with bacterial division, (p)ppGpp synthesis, wall and membrane biogenesis and, especially, lipopolysaccharide and peptidoglycan synthesis. These findings could be associated with growth arrest and witnessed transformation of the bacteria to a spore-like form. Unexpectedly, clusters of neighboring genes were differentially expressed. These clusters do not belong to operons or genetic networks; they have no evident associated functions and are not under the control of the same promoters. We also found undescribed but comparable clusters of regulation in previously reported transcriptomic analyses of intracellular bacteria, including Rickettsia sp. and Listeria monocytogenes. The transcriptomic patterns of C. burnetii observed under temperature stresses permits the recognition of unpredicted clusters of regulation for which the trigger mechanism remains unidentified but which may be the result of a new mechanism of epigenetic regulation.
Conflict of interest statement
Competing Interests: The authors have declared that no competing interests exist.
Figures
Figure 1. Eukaryotic RNA depletion and the atypical profile of C. burnetii rRNA.
(A) This figure represents the electrophoregram showing the overlap of total RNA after RNA extraction and bacterial RNA after eukaryotic RNA depletion. (B) This figure represents the electrophoregram showing the overlap of bacterial RNA after eukaryotic RNA depletion RNA and bacterial mRNA after bacterial rRNA depletion. (C) This figure represents the gel-like representation of the fractions obtained after the different RNA depletions.
Figure 2. Hierarchical clustering of differentially expressed genes.
CS30, CS 60, HS30 and HS60 represent the cold shock stress for 30 min and 60 min and the heat shock stress for 30 min and 60 min, respectively. Green plots represent genes that are downregulated upon temperature stress, red plots represent genes that are upregulated upon temperature stress, and gray plots represent genes with variable regulation observed in biological replicates (p>0,05).
Figure 3. Functional category classification of genes differentially expressed upon exposure to stress temperatures.
(A) The figure represents the proportion of genes differentially expressed according to the COG functional classification for each condition and genes differentially expressed at least one time in all of the conditions (All).
Figure 4. Transcriptional profiles of the early responses to temperature stress.
(A) The Outer circle represents the ORFing of C. burnetii genome. The blue, purple and black sections represent respectively the spotted ORF from the strand +, the spotted ORF from the strand – and the ORF not spotted. (B) The diagram represents the level of interactions with the other proteins based on String software. (C) The inner circles represent the transcriptomic profiles observed with the four tested conditions. The green, red and gray sections represent respectively the down-regulated, the up-regulated and the not regulated genes.
Figure 5. Distribution of differentially expressed genes.
This figure represents the total number of differentially expressed genes included in different window sizes (between 5 and 11 genes) that contain differentially expressed genes.
Figure 6. Transcriptional profiles from previously reported analyses of intracellular bacteria.
The Outer circle represents the ORFing of the different intracellular bacteria. The blue and purple sections represent respectively the spotted ORF from the strand + and the spotted ORF from the strand –. The inner circles represent the transcriptomic profiles observed in the different studies. The green, red and gray sections represent respectively the down-regulated, the up-regulated and the not regulated genes.
References
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