Table 1.

Levels of repA mRNA from autorepressed promoters: Effect of iteron numbers

	Integrated prophages in DH5Δlac
	λincCrepA-lacZ		λincCrepAincA-lacZ
lacZ activity (Miller units)*	14  ± 1.2	28  ± 2.6	13  ± 1.3	25  ± 0.36
Number of prophages (iterons)	1  (5)	2  (10)	1  (14)	2  (28)
Phage yield by ter assay†	<103	7  × 105	<103	7  × 105
Relative repA mRNA‡	1	1.5  ± 0.10	1.4  ± 0.26	1.5  ± 0.25
Transformants with pSP102	7  × 103	4  × 103	5  × 103§	<10
Transformants with pVM11¶	7  × 103	4  × 103	<10	<10

^*The activity was measured from log phase cultures grown in L broth (30) and units were used to estimate prophage numbers. The units may not be compared between the two prophages because a transcription terminator in incA and a damaged par promoter precedes lacZ in the incA carrying prophage (unpublished results). 

^†The assay helps to discriminate between mono- and poly-lysogens (13). 

^‡ RNA was measured by primer extension exactly as described for Fig. 3 by using aliquots from the same culture used for measuring lacZ activity. 

^§ As opposed to overnight for others, these colonies appeared after 48 hr at 37°C. 

^¶pVM11 is ΔrepAΔincA whereas pSP102 is ΔincA only.