RAPISARDA Viviana Andrea
congresos y reuniones científicas
Differential expression of the Escherichia coli NADH dehydrogenase-2 depending on the medium and the phase of growth
VOLENTINI, S. I.; RAPISARDA, V. A.; FARÍAS, R. N.; MASSA, E. M.; RODRÍGUEZ-MONTELONGO, L.
Iguazu, Misiones (Argentina)
Congreso; XL Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2004
NADH dehydrogenase-2 (NDH-2) of Escherichia coli is an enzyme of respiratory chain located in the plasmatic membrane and encoded by ndh gene. According to the bibliography, ndh gene is expressed only in exponential phase of growth due to the negative regulation of the global transcription factor FNR, in the absence of oxygen. In order to deepen the studies on expression, we worked with the strain JRG2689 that contains a plasmid with the b-galactosidase gene under the ndh promoter. We measured the b-galactosidase activity along growth curves and we proved that the expression profile of the enzyme was coincident with the data reported previously when the cells were growing in rich medium Luria Broth or in minimal medium MT. In both media an increase of the expression of the enzyme in the exponential phase of growth was followed by a decrease before entering the stationary phase. However, when the cells were growing in M9 minimal medium, the maximal expression was reached in early stationary phase and it was maintained in later stationary phase. These data were corroborated measuring the membrane NDH-2 activity in a wild type strain grew in the different media and harvested either in exponential or in stationary phase of growth. In this work we demonstrated that the expression pattern of NDH-2 during the growth curves depends on the media. Further studies should be done to elucidate the FNR involvement in these processes.