AtxA, a Bacillus anthracis global virulence regulator.

Fifteen years ago, AtxA was isolated as a toxin gene activator and five years later it was shown to be a Bacillus anthracis master regulator. AtxA controls the expression of more than a hundred genes belonging to all genetic elements, the chromosome and both virulence plasmids, including those encoding the major virulence factors. AtxA can activate or repress gene expression. The mechanism by which AtxA exerts its control is unknown; it is indirect on some genes but may be direct on others. The expression of many AtxA-controlled genes is induced by the presence of bicarbonate/CO(2). AtxA links the metabolic state and virulence gene expression.