SUMMARY: Mutants of mucoid defective in fructose-bisphosphate aldolase (FBA), NADP-linked glyceraldehyde-3-phosphate dehydrogenase (GAP) or 3-phosphoglycerate kinase (PGK) were unable to grow on gluconeogenic precursors like glutamate, succinate or lactate. The and mutants could grow on glucose, gluconate or glycerol, but mutants could not. This suggests that the metabolism of glucose or gluconate does not require either PGK or NADP-linked GAP but does require the operation of the aldolase-catalysed step. For gluconeogenesis, however, all three steps are essential. Recombinant plasmids carrying genes for FBA, PGK, GAP or phospho-2-keto-3-deoxygluconate aldolase (EDA) activities were constructed from a genomic library of mucoid selecting for complementation of deficiency mutations. Analysis of their complementation profile indicated that one group of plasmids carried and genes, while another group carried , 6-phosphogluconate dehydratase () and glucose-6-phosphate dehydrogenase () genes. The gap gene was not linked to any of these markers. Partial restoration of FBA activity in spontaneous revertants of Fba mutants was accompanied by a concomitant loss of PGK activity. These experiments indicate a linkage between the and genes on the chromosome.


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