a–c, 24-point MIC curves of wild-type E. coli and the five SPOCK assay hit strains that were used for follow-up investigation. Overnight cultures were inoculated 1/10,000 into fresh LB media in final volumes of 100 µl in 96-well microtiter plates, and antibiotic was added to the concentrations indicated. Cultures were incubated until untreated control cultures reached stationary phase, and optical density at 600 nm was measured (mean ± range; n = 2 biologically independent experiments). d–f, 12-point kill curves of wild-type E. coli and the five strains described above. Cultures were grown to stationary phase in LB media in final volumes of 100 µl in 96-well microtiter plates. Antibiotic was introduced at the concentrations noted, and cells were incubated for an additional 24 h prior to plating (mean ± range; n = 2 biologically independent experiments). We note here that perhaps because of its lack of cell envelope integrity in stationary phase, the ΔldcA strain displays promiscuous sensitivity to killing by ampicillin and gentamicin, in addition to ciprofloxacin, whereas ΔnlpI, ΔompR, ΔyfgL, and ΔyibP display stationary phase sensitivity to ciprofloxacin exclusively, relative to the wild type. LdcA (EMBO J. 18, 4108–4117; 1999), NlpI (Proc. Natl. Acad. Sci. USA 112, 10956–10961; 2015), and YibP (EnvC) (Mol. Microbiol. 52, 1255–1269; 2004) modulate peptidoglycan cross-linking and recycling, whereas OmpR (J. Biol. Chem. 277, 24155–24161; 2002) and YfgL (BamB) (Cell 121, 235–245; 2005) play roles in governing membrane protein composition.