Fructose metabolism in wild-type, fructokinase-negative and revertant strains of Rhizobium leguminosarum

Nitrogen Fixation Research Group, School of Environmental and Life Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia ABSTRACT SUMMARY: Rhizobium leguminosarum accumulates fructose by an active process sensitive to azide, 2,4-dinitrophenol and carbonyl cyanide m -chlorophenylhydrazone. The fructose is not phosphorylated during transport. Sorbose and glucose interfere with fructose uptake. Inside the cell fructose is metabolized via fructose 6-phosphate; there is no evidence for an alternative metabolic route via sorbitol to glucose or via sorbitol 6-phosphate to fructose 6-phosphate. Tn5-induced mutants lacking fructokinase failed to grow on fructose, mannitol or sorbitol and grew slowly on sucrose; growth was normal on all other single carbon sources tested. Growth of these mutants on a range of carbon sources was retarded by added fructose. Revertants which had regained the capacity to utilize fructose all had an unstable fructokinase which could be partially stabilized by fructose.