TABLE 2.

Effects of rlrA and rorA on the inheritance by spores of pSLA2 plasmids replicating in a circular mode

Expt no.	Plasmid	rlrA	rorA	Frequency of plasmid inheritance (%)a
1	pQC36	−	−	0.1
2	pQC125	+	−	0.005
3	pQC91	+	−	0.001
4	pQC61	−	+	0.7
5	pQC48	+	+	28
6	pQC101	+	+	78

^apSLA2 circular plasmids were introduced into ZX7, and thiostrepton-resistant colonies were inoculated into CM medium containing thiostrepton (23). After 7 days at 30°C, spores were streaked on CM plates without selection for 7 days at the same temperature. Harvested spores were diluted in water and plated equally on LB and on LB medium containing thiostrepton. After 3 days of incubation, we counted the number of colonies on plates. The frequency of plasmid inheritance = 100 × ratio of colonies on LB containing thiostrepton-resistant colonies on LB.