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.