Fig. 2.

Engineered bacteria sense and remember ATC exposure in vitro. (A) Schematic of experimental design, as described in Methods. (B) In vitro triggering of PAS132. (C) In vitro memory of ATC exposure. (D) PAS132 was grown in liquid culture in the presence of ATC at the indicated concentration for 4 h, then plated on M9 glucose X-gal plates to determine the minimum dose of ATC required to switch the cells from the cI state to the Cro state. For all panels, means ± SD of three or more independent samples are shown. (E) Competitive growth assay to compare fitness of parental and engineered E. coli strains (Results, Methods). Mixed cultures of MG1655 rpsL and PAS132 were titered before (gray bars) and after (black bars) subculturing with a 10¹⁵-fold net serial dilution.