Fig. 6. (A) Induction of the prespore marker psA-lacZ in cells of a random integrant and an Ax2/gskA– strain. Cells were developed in suspension culture and pulsed with 300 µM cAMP. Samples were taken at t=0 (–cAMP) and t=8 hours (+cAMP), and ß-galactosidase activity was determined. All samples were measured in triplicate and the means and standard deviations are presented. The accumulation of ß-galactosidase is higher in the gskA-null mutant than in the random integrant. This is likely to be due to copy number differences for the reporter construct in the two strains. (B) Induction of spore cell differentiation by 8-Bromo-cAMP in a random integrant and an Ax2/gskA– strain. The random integrant and Ax2-derived gskA-null mutant were plated at low density (10⁴ cells/cm²), in spore induction medium and exposed to 15 mM 8-bromo-cAMP for 24 hours (Kay, 1989). Spores were counted and expressed as a percentage of total number plated. Data are expressed as mean number±s.e.m. (n=3).