FIG 4.

Virulence phenotypes associated with genes differentially expressed in the B. abortus ybeY deletion strain. Cultured peritoneal macrophages from BALB/c mice were infected with B. abortus 2308 or with isogenic deletion strain B. abortus Δbab2_0822, B. abortus Δbab2_1109, or B. abortus Δbab2_0700. At 2, 24, and 48 h postinfection, the macrophages were lysed, and the number of intracellular brucellae present in these phagocytes was determined by serial dilution and plating on agar medium. The asterisk denotes a statistically significant difference (P < 0.05; Student's t test) between the isogenic deletion strains and parental strain 2308 at 48 h postinfection.