Regulation by metals of phosphate-dependent ndh expression in Escherichia coli

GRILLO PUERTAS, MARIANA; SCHURIG-BRICCIO, LICI ARIANE; RODRIGUEZ-MONTELONGO, LUISA; RINTOUL, MARIA REGINA; RAPISARDA, VIVIANA ANDREA

Córdoba

Congreso; SAIB; 2009

SAIB

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The ndh gene, which codified NADH dehydrogenase-2 in E. coli, is highly regulated at transcriptional level by diverse external stimuli. Our laboratory reported that ndh expression was maintained in stationary phase when cells were grown in the presence of at least 37 mM phosphate. Preliminary observations also indicated that ndh expression was decreased when cells were grown in the presence of copper. The aim of this work was to study the regulation of phosphate-dependent ndh expression during stationary phase by transition metals. The experiments were performed using chromosomal fusions of the complete promoter or its deletions with lacZ. A concentrations range of Cu2+ was added at different times of growth. b-Galactosidase activity and viability were determined. In exponential phase cells, ndh expression was not regulated by copper. However, during stationary phase, the phosphate-dependent gene expression was totally repressed when cells were incubated for 1 h with 1 mM CuSO4. This copper effect was also observed with ndh  promoter deletions from -250 to -100. Viability was not modified in any of the conditions tested. To analyze a possible copper-specific ndh repression, others metals that regulate metal-responsive promoters were assayed. Further studies should be done to elucidate this metal-mediated regulation of ndh during stationary phase.