METABOLISM OF AMINO ACIDS IN AGROBACTERIUM TUMEFACIENS: I. UPTAKE OF L-VALINE BY RESTING CELLS

Abstract

The characteristics of14C-valine uptake by Agrobacterium tumefaciens are described. Highly significant differences were observed with the non-tumorogenic strain IIBNV6and the tumorogenic strain IIBV7K.Resting cells of strain IIBNV6displayed an amino acid uptake pattern, energy requirement, pool saturation, and substrate specificity typical of bacteria (e.g. Escherichia colt) which have been studied previously. In contrast, cells of the strain IIBV7K exhibited an apparent independence from external energy requirements and showed a non-specific competition by structurally unrelated amino acids for14C-valine uptake.In cells of this tumorogenic strain,14C-valine was metabolized after its uptake from the medium, and the metabolic product was effluxed into the extracellular fluid. This product was identified as α-ketoisovaleric acid. Cells of the strain IIBV7K were unable to accumulate this keto acid, although IIBNV6cells took it up readily.Valine uptake by IIBV7K cells was inhibited by a host of structurally unrelated amino acids, which were able to displace the accumulated valine from these cells.The deamination of valine to α-ketoisovaleric acid appears to be associated with a transaminase-type reaction in cells of the strain IIBV7K. Hydroxylamine inhibited the efflux of the product in this strain, whereas in the non-tumorogenic strain it inhibited14C-valine uptake.