FIG. 6.

TraM inhibits basal levels of TraR and modulates the activity of induced levels of TraR in controlling Ti plasmid conjugative transfer. Cultures of A. tumefaciens NTL4 harboring one or more plasmids, as indicated, coding for traR (pSRKGmtraR), traM (pYZ1), and a TraR-dependent traA::lacZ reporter fusion (pZLB251) were grown in MG/L medium supplemented with IPTG (1 mM), N-(3-oxo-octanoyl)-l-HSL (AAI; 10 or 100 nM as noted), or both, as indicated, for 4 h; samples were harvested; and the cells were assayed for β-galactosidase activity. Enzyme activity is expressed as Miller units. Error bars show standard deviations.