FIG. 3.

Phenotype of the B. anthracis BA1877 deletion strain. The parental strain 34F2 (A and C) and the 34F2ΔBA1877 deletion strain (B and D) were grown on SM agar plates for 48 h (A and B) or in SM liquid medium for 9 h (C and D) at 37°C. (A and B) Plates were photographed with an AlphaInnotech imaging system. Two representative papillae are indicated by the arrows. (C and D) Samples were analyzed with a phase-contrast microscope. The images shown are representative of multiple images taken for both strains. Phase-bright spores (some indicated by the arrows) were found at a higher frequency (at least 20-fold) in fields of 34F2ΔBA1877 cells than in fields of 34F2 cells.