FIG. 2.

Developmental expression of Tn5 lac Ω4406 compared with the 3.2-kb Ω4406 upstream segment fused to lacZ. Developmental β-galactosidase specific activity was measured as described previously (28) for Tn5 lac-containing strain DK4294 (•) and for M. xanthus DK1622 containing a single copy of the 3.2-kb Ω4406 upstream DNA fused to promoterless lacZ within pREG1666 and integrated at Mx8 attB (▪; points are the average for three independent transductants). β-galactosidase specific activity is expressed in nanomoles of o-nitrophenyl phosphate per minute per milligram of protein.