Figure 3

The overproduction of RibM allowed growth of a Δ ribU ::Kan^r Δ ribB ::Erm^r Bacillus subtilis strain. Streaks (top) and drops (bottom, about 50,000 cells) of B. subtilis ΔribU::Kan^r ΔribB::Erm^r cells expressing ribM from plasmid pHT01ribM_opt were applied to LB plates (about 0.5 μM riboflavin) containing the indicated (additional) amount of riboflavin and 100 μM IPTG. Growth was recorded after incubation for 36 h at 37°C. As controls, strains were transformed with the empty vector pHT01. Apparently, only the strains transformed with pHT01ribM_opt could grow on culture media (LB) with low amounts of riboflavin.