Selection of lacZ operon fusions in genes of gluconate metabolism in E. coli. characterization of a gntT::lacZ fusion.

The initial steps involved in the utilization of gluconate by E. coli, its incorporation into the cell and subsequent phosphorylation to gluconate 6-phosphate, conform two systems that duplicate activities. These systems, GntI and GntII, are specified by two sets of genes distinctly regulated and located respectively at the malA-asd (75 min) and fdp-valS (96 min) regions of the bacterial chromosome. The presence of duplicate activities in the metabolism of gluconate of E. coli, has made difficult the study of the expression and participation of the GntI and GntII systems. In order to advance in this respect, the phage lambda placMu53 was used to select operon gnt::lacZ fusion in a E. coli strain delta (edd-zwf), delta (gnd-his), delta lac. Here we report the study of a gntT::lacZ fusion. This transductant allowed to differentiate the inducible expression of the gntT and gntU genes. Its characteristics, in agreement with previous reports, support the central role of the gntT gene in this metabolism.