Regulation of the Escherichia coli NADH dehydrogenase-2 gene expression by phosphate and glycerol.

SCHURIG-BRICCIO, L. A.; RINTOUL, M. R.; BALDOMA, L.; BADIA, J.; RODRÍGUEZ-MONTELONGO, L.; RAPISARDA V. A.

Rosario

Congreso; XLII Reunión Anual de SAIB; 2006

SAIB

 NADH dehydrogenase-2 of Escherichia coli, encoded by ndh gene, is used during aerobic and nitrate respiration. The expression of ndh, is subject to a complex network of regulatory controls at the transcriptional level. It was reported that the gene, is expressed mainly in exponential phase of growth and that its expression decays in stationary phase by the regulation of several transcriptional factors (i.e.: FNR, IHF, Fis, etc.). However, in our current studies of NDH-2 activity, we found that expression was maintained up to stationary phase. These contradictory observations are based on the different culture media used: M9 minimal medium in our assays or LB complete medium in previous reports. By comparative expression of transcriptional fusions in different minimal media, we determined that the maintenance of NDH-2 activity in stationary phase depends on the presence of at least 25 mM phosphate. Besides phosphate, glycerol was also required. No correlation between the differential expression and the identified transcriptional factors was found by analysis with several chromosomal mutants. Deletion analysis of the ndh promoter region allowed us to recognise nucleotides from -255 to -205 as essential for the regulation by phosphate and glycerol. Our results suggest that glycerol-phosphate is a key compound in the regulation of ndh gene.