Fig 3.

Effect of B. anthracis on amoeba viability. (A) Representative phase-contrast images (Axio Imager; 63× objective) of A. castellanii cultured with or without the indicated B. anthracis strains for 24 h at 37°C. Insets are ×10 enlargements of a subsection of the larger photograph (dashed box). (B) Representative phase-contrast image (Axio Imager; 63× objective) of B. anthracis filaments undergoing sporulation after 12 h of coculture with A. castellanii at 37°C. r, spores being released from the mother cell. (C) The number of viable A. castellanii amoebas cocultured without bacteria (amoeba only) or with Sterne 7702, TKO, or 9131 at the indicated times at 37°C was quantified using a hemacytometer and trypan blue staining.