Bacillus anthracis, the etiological agent of anthrax, is a Gram-positive sporulating bacterium. Its life-cycle can be divided schematically into two phases: multiplication in the mammalian host and persistence in the soil. A central regulator AtxA interferes with expression of more than 70 genes in vitro and an undefined number ex vivo. The exact molecular mechanism of action of AtxA is unknown, but the involvement of cascades of relay regulators has been described. Other regulators have also been implicated in the regulatory networks; these are mainly transition state regulators, which have been studied in other Bacillus species. They contribute to the regulation of expression of virulence- and persistence-factor genes, and to the regulation of atxA itself.