Figure 5.

High ATP and low proline promote transcription of the mgtCBR coding region in an independent and additive manner. A. Fluorescence produced by an adenine auxotroph (EG9652) harbouring plasmid pGFP303 with the PhoP-dependent mgtCBR promoter and wild-type mgtCBR leader fused to a promoterless gfp gene, the plasmid vector pfpv25, or pGFP303 derivatives with conserved A nucleotides at position 44–46 substituted by Ts (pGFP303 A_44–46→T) or with the three mgtP Pro codons substituted by Gly codons (pGFP303 mgtP_Pro→Gly). Bacteria were grown in N-minimal media with 10 µM Mg²⁺ in the presence of either 25 µM or 250 µM adenine. Fluorescence was monitored following growth for 6.5 h with shaking at 37°C under microaerophilic conditions in a Victor³ plate reader. Data correspond to a representative of four independent experiments. B. mRNA levels of the coding regions of the mgtC gene produced by a proline and adenine auxotroph (EL333) grown under different combinations of high and low levels proline and adenine. The RNA values were normalized relative to those corresponding to the rrs gene. Bacteria were grown in N-minimal media with 500 µM Mg²⁺ in the presence of 1 mM proline and 25 µM adenine for 1 h, and then grown for 1 h in media either containing or lacking proline, 25 µM or 250 µM adenine.