DIFFERENTIAL EXPRESSION OF THE Escherichia coli NADH DEHYDROGENASE-2

VOLENTINI SI; RAPISARDA VA; FARIAS RN; MASSA EM; RODRIGUEZ MONTELONGO L

Iguazu, Misiones

Congreso; Reunion Anual de SAIB; 2004

SAIB

  NADH dehydrogenase-2 (NDH-2) of Escherichia coli is an enzyme of the respiratory chain, coded by ndh gene. According to the bibliography, ndh is expressed only in exponential phase of growth due to the negative regulation of the global transcription factor FNR, in the absence of oxygen and iron-limitation in stationary phase. In order to deepen the studies on expression, we worked with a strain that contains a plasmid with the lacZ gene under the ndh promoter. We measured the b-galactosidase activity along growth curves and we saw that the expression profile of the enzyme was coincident with the data reported previously when the cells were growing in LB (rich medium) or in MT (minimal medium). However, when the cells were growing in M9 minimal medium, the maximum level of 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 participation of FNR, oxygen and metals in these processes.