RpoN expression. (a) RpoN expression under different growth conditions. 1: NBAF; 2: NBH2F; 3: NBLF; 4: ammonium-free NBAF; 5: FWAFC; 6: FWH2FC; 7: FWLFC; 8: FWAF; 9: FWH2F; 10: FWLF. Media abbreviations were detailed in Methods. (b) RpoN over-expression. Total protein (5 μg) was separated by 10% SDS-PAGE and analyzed by Western blot analysis with the RpoN-specific antiserum. Two biological samples were shown for IPTG-induced WTV and RpoN+ strains. IPTG was added at final concentration 1 mM.