FIG. 6.

Kinetics of cpe gene expression and CPE production by DS cultures of SM101. (A) RT-PCR analysis of cpe gene transcription in cultures growing from 1 to 7 h in DS medium at 37°C. The spo0A gene was used as a housekeeping gene, and a sample lacking reverse transcriptase (−RT) was run to show the absence of DNA contamination in these samples. The sizes of products, based on comparison against DNA size markers (not shown), are shown to the right of each gel. (B) Western blot analyses of CPE production after 1 to 7 h of growth in DS medium at 37°C. To show that CPE production is dependent on sporulation, this figure shows the absence of CPE production by an 8-h culture of SM101 grown at 37°C in TGY, a medium that does not induce sporulation. The size of the immunoreactive protein, based on the migration of prestained markers (not shown), is indicated on the right.