FIG. 9.

Effect of orf2 on developmental expression of orf1-lacZ fusions. (A) Developmental expression from the wild-type 2.4-kb Ω4406 upstream DNA segment (▪) or its derivative with a stop codon mutation in orf2 (□), fused to lacZ in pPV12K and integrated at Mx8 attB. Average β-galactosidase specific activity is shown for three independently isolated transformants (Materials and Methods). (B) Developmental lacZ expression from Tn5 lac Ω4406-Tc^r (inserted in orf1) in M. xanthus with orf2 disrupted by plasmid integration. The arrangement of M. xanthus DNA (thin line) and plasmid vector DNA (thick line) is shown at the top. The triangle shows the position of Tn5 lac Ω4406-Tc^r. The graph shows the average β-galactosidase specific activity of three independently isolated transformants with this structure (▪) (Materials and Methods). As a control, developmental β-galactosidase specific activity was measured for Tn5 lac Ω4406-Tc^r-containing strain MJL100 (○). In both panels, β-galactosidase specific activity is expressed in nanomoles of o-nitrophenyl phosphate per minute per milligram of protein, and error bars show 1 standard deviation of the data.