FIG. 7.

Apparent spore viability of (A) and DPA level in (B) sleB spoVF sspA sspB spores made with different DPA concentrations. (A) Spores of strain PS3664 (sleB spoVF sspA sspB) were sporulated for 1.5 days with different DPA concentrations, the spores were purified and applied to LB medium plates without (•) or after (○) prior treatment with Ca-DPA, and colonies were counted after incubation for ∼24 h at 37°C as described in Materials and Methods. Spore viability was expressed relative to that of spores prepared with 300 μg/ml DPA and applied to plates after Ca-DPA treatment, and this value was set as 100%. The actual viability of the latter spores was essentially identical to that for wild-type spores (±25%). (B) The DPA levels in individual spores prepared with different DPA concentrations were determined by LTRS as described in Materials and Methods. The DPA level in spores prepared with 300 μg/ml DPA in the sporulation medium was set at 100%, and values for all other spore preparations were expressed relative to this value. The symbols used are: ○, percentage of spores that contain DPA; •, level of DPA in those spores that have DPA. 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.