Bacitracin resistance of various B. subtilis strains.

The names of the proteins introduced into B. subtilis to completely or partly replace the B. subtilis BceAB transporter and the species to which they belong are indicated between brackets on the left of the table. All MSD proteins are members of sub-family IV except NP_391349, which belongs to sub-family III. Strains (ri means that the corresponding ABC transporter was reconstituted/introduced into the appropriate B. subtilis background, see Table S2) were grown in medium alone (−IPTG) or in medium containing 1 mM IPTG (+ IPTG) to induce bceR expression and then tested to determine their bacitracin resistance in 96-well microtiter trays [22]. At the end of the incubation period, OD at 600 nm was monitored using a TECAN microtiter tray reader. IC50 is defined as bacitracin concentration (µg.ml−1) giving 50% growth inhibition. Results are expressed as mean IC50 values obtained in at least 3 different experiments ± standard deviations. The ratio (IC50 with IPTG (+)/IC50 without IPTG (−)) is given in the case of IC50 values >5 (nc: not calculated).