Colicin Sensitivity Assay for Salmonella

Colicin sensitivity was assayed as described (Nedialkova et al., 2014 (link)). Briefly, an overnight culture of colicin-producing Salmonella enterica serovar Typhimurium strain SL1344 (Spriewald et al., 2015 (link)) was diluted to OD_600nm = 0.8, 25 μL was spotted in the center of LB agar plates containing 0.5 μg/mL mitomycin C (Sigma-Aldrich) and 100 μM diethylenetriamine pentaacetic acid (DTPA; Sigma-Aldrich), and grown overnight for 20 h at 37°C. To 10 mL of top agar (0.75% agar), 10 μL of an overnight culture of an individual S. Reading isolate (tester isolate) was added and gently vortexed. The top agar containing the S. Reading isolate was poured onto the plate previously spotted with strain SL1344, incubated for 20 h at 37°C, and the formation of an inhibition zone (halo) around colicin-producing SL1344 was measured to determine the sensitivity of each S. Reading isolate.