Glycolate metabolism in cyanobacteria. IV. Uptake, growth and metabolic pathways

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Abstract
Anacystis nidulans (UTEX 625) and Anabaena cylindrical (CCAP 1403/2a) incorporated minor quantities of [14C]‐glycolate via diffusion, whereas Plectonema boryanum (PCC 73110) and Nostoc 268 rapidly incorporated [14C]‐glycolate. A carrier mediated uptake across the membrane is suggested for the two latter strains. In these strains the initial [14C]‐glycolate incorporation (>30 s) was inhibited by the uncoupler m‐chlorophenylhydrazone and the F0F1‐ATPase inhibitor N,N′‐dicyelohcxylearbodiimide (DCCD) but was not affected by inhibitors of glycolate metabolism: 2‐pvridyl‐hydroxymethanesulfonic acid (HPMS), glycidate, aminooxyacetic acid and aminoacetoniirile. The incorporation rate was about 0.5 and 40 umol (ma chl a)−1 h−1 at 17 μM and 5 mM glycolate, respectively, Anacystis nidulans did not grow on gtycolate. whereas Anabaena cylindrical to some extent did which suggests an inducible glycolate uptake system in this strain. Anahaena 7120 and Nostoc 268 grew photoheterotrophically on glycolate. The reduced [14C]‐glvcolale uptake by Anabaena 7120 in the presence of glycidate. aminooxyaeetic acid and aminoacetonitrile indicates that in the light, a large part of the [14C]‐glycolate incorporated was metabolized via glycine to serine. The net uptake of [14C]‐glycolate and the effect of different inhibitors was dependent on the source of nitrogen used (for growth and the nitrogen status during the assay. In cells cultivated in N‐free medium (nitrogen‐fixing cells) a larger part of the [14C]‐glycolate seemed to be metabolized via glycine to serine compared to that in cells cultivated in presence of NH4Cl (nonnitrogen‐fixing cells). The capacity to incorporate [14C]‐glyeolate by non‐nitrouen‐fixing cells was enhanced in presence of NH4CI.