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Uric acid utilization in Platymonas convolutae and symbiotic Convoluta roscoffensis

  • A. E. Douglas (a1)

Abstract

Uric acid is an excellent nitrogen source for the growth of cultures of Platymonas convolutae, the symbiotic alga from Convoluta roscoffensis, and related Platymonas and Tetraselmis species. Nitrate-grown cells of P. convolutae and T. tetrathele have two uptake systems for uric acid, which conform to Michaelis–Menten kinetics; a high-affinity system operating in the concentration range 0·2–4·5 μM a nd a low-affinity system operating at higher concentrations of uric acid. Uric acid uptake by P. convolutae is abolished by uncouplers of phosphorylation. In darkness, intact cells of P. convolutae metabolize [2-14C]uric acid to [14C]carbon dioxide. These results are consistent with the proposal that the algal symbionts of C. roscoffensis utilize uric acid, received from the host, as a nitrogen source.

Aposymbiotic juvenile and symbiotic adult C. roscoffensis under standard culture conditions contain uric acid. The solid uric acid content of juveniles declines on establishment of symbiosis with P. convolutae and the endogenous uric acid is utilized in the adult symbiosis under conditions of nitrogen demand. However, adult C. roscoffensis do not utilize exogenous uric acid. The growth of adult but not juvenile C. roscoffensis is dependent on nitrogen enrichment of the medium, and it is proposed that uric acid utilization is of significance to the growth of the developing symbiosis in a nitrogen-poor environment.

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Uric acid utilization in Platymonas convolutae and symbiotic Convoluta roscoffensis

  • A. E. Douglas (a1)

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