Nitrogen sources that were differentially used by the σ54 mutanta

Nitrogen sourceUtilization
Wild typeσ54 mutantComplemented σ54 mutant
15 mM NH4Cl+++
0.3 mM NH4Clb++
15 mM NO3++
7.5 mM urea++
3.75 mM agmatine+++
7.5 mM l-ornithinec++
15 mM l-serinec++
  • a Growth was assessed by measuring the optical density at 600 nm after incubation of cells in 4 ml minimal medium supplemented with the indicated nitrogen source for 24 h at 37°C and 220 rpm. +, utilization (OD600 > 0.36); −, no utilization (OD600 < 0.36).

  • b Growth was assessed in 100 ml minimal medium (500-ml Erlenmeyer flask).

  • c Growth with l-ornithine or l-serine as the nitrogen source was assessed for 36 h.