FIG. 4.

Colony formation from (A) and DPA level in (B) ger3 sleB spoVF spores prepared with different DPA concentrations. (A) Strain PS4138 (ger3 sleB spoVF) was sporulated for 2 days with different DPA concentrations, spores were purified, aliquots were applied to LB medium agar plates without (○) or after (•) pretreatment with Ca-DPA, and colonies were counted after incubation for ∼24 h at 37°C. Spore viability is expressed relative to that of spores made with 300 μg/ml DPA plated without Ca-DPA treatment, which was set at 100%. (B) The level of DPA in ∼200 PS4138 spores made at different DPA concentrations was determined by LTRS as described in Materials and Methods. ○, percentage of spores that contain DPA; •, level of DPA in spores that contain DPA. All values for DPA levels are expressed relative to the level in spores made with 300 μg/ml DPA, which was set at 100%. Note that for spores made with no added DPA, the data have been plotted as if the DPA concentration in the medium was 0.1 μg/ml in order to readily display all the data.