TABLE 1.

B. anthracis strains used in this study

Strain	Description	Source or reference
B. anthracis Ames	Fully virulent; pXO1+ pXO2+	40
B. anthracis Sterne	Attenuated; pXO1+ pXO2−	40
purH::Kan strain	B. anthracis Ames containing an Ω-Kan-2 fragment insertion in the purH gene	This paper
ΔpurH strain	B. anthracis Ames containing an Ω-Kan-2 fragment replacement of the purH gene	This paper
ΔpurD strain	B. anthracis Ames containing an Ω-Kan-2 fragment replacement of the purD gene	This paper
ΔpurH + purH strain	ΔpurH strain genetically complemented with native purH on the pEO3 plasmid	This paper
ΔpurH + purD strain	ΔpurH strain genetically complemented with native purD on the pEO3 plasmid	This paper
ΔpurD + purD strain	ΔpurD strain genetically complemented with native purD on the pEO3 plasmid	This paper