Regulation of virulence in Bacillus anthracis: the phosphotransferase system transmits the signals.

Bacillus anthracis causes host damage by producing two toxins, the lethal factor and the oedema factor. Their production and that of other virulence factors depend on the activity of the AtxA transcription factor. The mechanisms that control AtxA activity are reported in this issue of Molecular Microbiology. The protein can be phosphorylated at two distinct sites by components of the phosphotransferase system (PTS). One phosphorylation event stimulates transcription activation by AtxA, whereas the second prevents AtxA activity. This mode of regulation and the predicted domain structures are highly similar to transcription regulators controlled by PTS regulation domains (PRDs). Thus, the phosphorylated domains of AtxA represent a novel form of PRDs. As a similar organization is found in transcription regulators in many other pathogens, AtxA might become the paradigm of a new class of virulence regulators.