Microbiology

Anthrax Regulation

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Science  28 Feb 2003:
Vol. 299, Issue 5611, pp. 1285
DOI: 10.1126/science.299.5611.1285b

Bacillus anthracis is distinguished from its more benign relations among the bacilli by the possession of plasmids containing virulence genes. The virulence genes are transcribed in response to elevated environmental temperature and carbon dioxide levels—key host signals. The plasmid pXO1 carries the anthrax toxin gene and its regulating genes. Mignot et al. have discovered that the toxin gene regulator AtxA on the plasmid also regulates the expression of cell surface proteins of the semicrystalline S-layer, via the PagR transcription factor. In the presence of carbon dioxide only one of the S-layer genes is expressed. The S-layer genes are on the bacterial chromosome, so AtxA appears to be a master regulator on the plasmid coordinating the expression of many genes throughout the genome, leading to successful infection. The need for B. anthracis to shift S-layer type in vivo may relate to structural constraints on toxin secretion. So, plasmids alone do not a pathogen make. — CA

Mol. Microbiol. 47, 917 (2003).

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