Pentose Metabolism in Rhizobium leguminosarum MNF300 and in Cowpea Rhizobium NGR234
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L-Arabinose is broken down by Rhizobium leguminosarum MNF300 via 2-oxoglutarate semialdehyde. Enzyme activities in cells grown on succinate, mannitol or arabinose indicated much greater modulation of arabinonate dehydratase, 2-keto-3-deoxyarabinonate dehydratase and 2-oxoglutarate semialdehyde dehydrogenase than of arabinose dehydrogenase or of arabinono-γ-lactonase. In cowpea Rhizobium NGR234, all the enzymes of L-arabinose metabolism except L-arabinono-γ-lactonase were inducible. Assays for such enzymes in snake bean bacteroids indicated that L-arabinose did not reach the bacteroids in large quantities. The Tn5-induced mutant MNF3045 of R. leguminosarum was unable to grow on L-arabinose and accumulated L-arabinono-γ-lactone and L-arabinonate. Product accumulation and enzyme assays suggested that this mutant was defective in L-arabinonate dehydratase. It nodulated peas and the nodules fixed N2, indicating that the supply of L-arabinose is not essential for bacteroid function. Another Tn5-induced mutant of R. leguminosarum, MNF3041, lacked ribokinase and was unable to grow on D-ribose; this mutant was also able to nodulate peas and fix N2.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Environmental and Life Sciences|
|Publisher:||Society for General Microbiology|
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