Table 1.

Indole rescue phenotypes of E. coli strain K12ΔHIΔtrp with and without complementation by vector pCDS5KO::trpRBA.

Strain	Minimal medium M9	M9 + Tryptophan	M9 + Indole
K12ΔHIΔtrp	−	+	−
K12ΔHIΔtrp/pCDS5KO::trpRBA	−	+	+

E. coli strains were grown on minimal medium M9 agar plates, with and without supplementation by tryptophan or indole. After incubation for 24 h, growth was assessed visually and is indicated by +/− (growth/no growth). Both strains grew in the presence of tryptophan and neither grew in the absence of tryptophan or indole. Only K12ΔHIΔtrp/pCDS5KO::trpRBA was able to grow in the absence of tryptophan when supplemented with indole.