Transcriptome analysis identifies Bacillus anthracis genes that respond to CO2 through an AtxA-dependent mechanism

BMC Genomics

Stephen H Leppla²  Stephen F Porcella¹  Sarah Anzick¹  Kimmo Virtaneva¹  Stacy M Ricklefs¹  Craig Martens¹  Inka Sastalla²  Andrei P Pomerantsev³  Andrew T McKenzie² 

[1] Genomics Unit, Research Technologies Section, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT 59840, USA;Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA;National Institutes of Health, 33 North Drive, Building 33, Room 1W20B, Bethesda, MD 20892, USA

关键词: Gene-environment interaction;    Small RNA;    Toxin production;    AtxA;    RNA sequencing;    Illumina;    pXO1;    Bacillus anthracis;   

Others  :  1217646
DOI  :  10.1186/1471-2164-15-229

 received in 2013-07-09, accepted in 2014-03-12,  发布年份 2014

【 摘 要 】

Background

Upon infection of a mammalian host, Bacillus anthracis responds to host cues, and particularly to elevated temperature (37°C) and bicarbonate/CO₂ concentrations, with increased expression of virulence factors that include the anthrax toxins and extracellular capsular layer. This response requires the presence of the pXO1 virulence plasmid-encoded pleiotropic regulator AtxA. To better understand the genetic basis of this response, we utilized a controlled in vitro system and Next Generation sequencing to determine and compare RNA expression profiles of the parental strain and an isogenic AtxA-deficient strain in a 2 × 2 factorial design with growth environments containing or lacking carbon dioxide.

Results

We found 15 pXO1-encoded genes and 3 chromosomal genes that were strongly regulated by the separate or synergistic actions of AtxA and carbon dioxide. The majority of the regulated genes responded to both AtxA and carbon dioxide rather than to just one of these factors. Interestingly, we identified two previously unrecognized small RNAs that are highly expressed under physiological carbon dioxide concentrations in an AtxA-dependent manner. Expression levels of the two small RNAs were found to be higher than that of any other gene differentially expressed in response to these conditions. Secondary structure and small RNA-mRNA binding predictions for the two small RNAs suggest that they may perform important functions in regulating B. anthracis virulence.

Conclusions

A majority of genes on the virulence plasmid pXO1 that are regulated by the presence of either CO₂ or AtxA separately are also regulated synergistically in the presence of both. These results also elucidate novel pXO1-encoded small RNAs that are associated with virulence conditions.

【 授权许可】

   
2014 McKenzie et al.; licensee BioMed Central Ltd.

【 图 表 】

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