Activation of the latent PlcR regulon in Bacillus anthracis.
Many genes in Bacillus cereus and Bacillus thuringiensis are under the control of the transcriptional regulator PlcR and its regulatory peptide, PapR. In Bacillus anthracis, the causative agent of anthrax, PlcR is inactivated by truncation, and consequently genes having PlcR binding sites are expressed at very low levels when compared with B. cereus. We found that activation of the PlcR regulon in B. anthracis by expression of a PlcR-PapR fusion protein does not alter sporulation in strains containing the virulence plasmid pXO1 and thereby the global regulator AtxA. Using comparative 2D gel electrophoresis, we showed that activation of the PlcR regulon in B. anthracis leads to upregulation of many proteins found in the secretome of B. cereus, including phospholipases and proteases, such as the putative protease BA1995. Transcriptional analysis demonstrated expression of BA1995 to be dependent on PlcR-PapR, even though the putative PlcR recognition site of the BA1995 gene does not exactly match the PlcR consensus sequence, explaining why this protein had escaped recognition as belonging to the PlcR regulon. Additionally, while transcription of major PlcR-dependent haemolysins, sphingomyelinase and anthrolysin O is enhanced in response to PlcR activation in B. anthracis, only anthrolysin O contributes significantly to lysis of human erythrocytes. In contrast, the toxicity of bacterial culture supernatants from a PlcR-positive strain towards murine macrophages occurred independently of anthrolysin O expression in vitro and in vivo.
Sastalla
Inka
I
Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Maltese
Lauren M
LM
Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Pomerantseva
Olga M
OM
Biological Defense Research Directorate, Naval Medical Research Center, Rockville, MD, USA.
Pomerantsev
Andrei P
AP
Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
Keane-Myers
Andrea
A
Biological Defense Research Directorate, Naval Medical Research Center, Rockville, MD, USA.
Leppla
Stephen H
SH
Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
D000595:Amino Acid Sequence; D000818:Animals; D000881:Anthrax / Q000382:microbiology; D001408:Bacillus anthracis / Q000235:genetics* / Q000472:pathogenicity; D001409:Bacillus cereus / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D018085:Regulon; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
C082932:ATXA protein, Bacillus anthracis; D001426:Bacterial Proteins; C099480:PlcR protein, Bacillus; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators