FIGURE 4.

Combined activation of promoters in an operon. (A) RT-qPCR analysis of expression levels of the seven operon genes in the activation mutants after 48 h of incubation. The expressions of the seven operon genes in M. xanthus ZE9 were each set as 1, and the expressions of the genes in mutant strains are shown as the relative expression. (B) Yields of epothilone A and epothilone B in M. xanthus ZE9 and the activation mutants. The error bars represent the standard deviation of three independent experiments. For statistical analysis between the ancestral strain and mutant strains, the signals of ** and * mean p < 0.01 and p < 0.05, respectively.