Stimulation of nitrogenase activity and photosynthesis in some cyanobacteria by glyoxylate

Abstract

The effect og glyoxylate on nitrogenase activity (C2H2 reduction) and photosynthesis (H14CO3 fixation and O2 evolution) was in vestigated in the three heterocystous cyanobacteria Anabaena cylindrica, A. variabiltis and N. muscorum. Glyoxylate had virtually no effect on the rate of dark respiration and was unable to sustain photoheterotrophic growth, though some slight stimulation (= 30%) of photorophic growth was noted. A considerable stimulation of both nitrogenase and photosynthetic activities was observed in presence of glyoxylate. In the light the stimulation increased with time up to about 15‐25 h after adding optimal concentrations of 4–6 mM glyoxylate. Placing glyoxylate treated samples in the dark or adding DCMU (30 μM) in the light, showed that glyoxylate initially supported significantly higher nitrogenase activity than did samples in absence of glyoxylate. However, after a prolonged incubation in the dark or in presence of DCMU glyoxylate is unable to relieve the adverse effects of such conditions. The stimulation of the nitrogenase activity was even more pronounced when the glyoxylate was added to cells preincubated in the dark (“carbon starved”) than for cells kept constantly in light. The results suggest that glyoxylate, or a metabolite, may act as an inhibitor of cyanobacterial photorespiration and this hypothesis is discussed.

Glyoxylate Induced Changes in the Carbon and Nitrogen Metabolism of the Cyanobacterium Anabaena cylindrica

“…This pigment is an easily mobilized nitrogen reserve in cyanobacteria. As noted earlier (3,4), the Chl a content slightly increased initially, but decreased in long-term experiments (more than a 24-h treatment). The ratio of Chl a to phycocyanin was always higher if glyoxylate was present (Table II).…”

“…Increased glycolate excretion was earlier found in Anabaena when glyoxylate was present (6). Na glycolate given at 2, 5, 10, and 20 mm caused some stimulation in both N2 and CO2 fixation, but glyoxylate given at equimolar concentrations caused several-fold larger effects (3,4). Moreover, glycolate was without effect on the MSX-induced release of NH4+, while glyoxylate slightly stimulated NH4' release (5 (5,7,16).…”

“…A stimulation of CO2 fixation by glyoxylate has been noted in the cyanobacterium Anabaena cylindrica (3,4), and in several eucaryotic systems, e.g. tobacco (21,23), soybean cells (16,22), and spinach cells (17).…”

“…Glyoxylate is known to stimulate the nitrogenase activity (3,4,28) Sodium glyoxylate was treated and used as given in (3). Transmission electron microscopy of the cyanobacterium was as described in Sharma et al (26).…”

Effects of Aminooxyacetate and Aminoacetonitrile on Glycolate and Ammonia Release by the Cyanobacterium Anabaena cylindrica

“…Cells were grown in pure culture in either NH4Cl-supplemented (N+) or N-free (N-) BG 11 medium (26) and sparged continuously with sterile air. Cultivation and cell harvesting from N+ and N-media were carried out as detailed earlier (1,3,4). The N+-grown cultures were used in experiments on the release of ammonium and amino acid pool sizes, while N-grown cells were used in the remainder of the experiments.…”