Ascorbic Acid and Heterocyst Development in the Blue–Green Alga Amabaema ambigua

Abstract

AbstraetThe nitrogen-fixing blue-green alga Anabaena ambigua was grown in a medium which contained either ammonium chloride as nitrogen source or molecular nitrogen. In the latter case the alga produced heterocysts. The material was analysed for ascorbic acid, dehydro-ascorbic acid and diketogulotiic acid. The amount of ascorbic acid was found always to be higher in the alga grown with molecular nitrogen. When the alga grown with combined nitrogen was transferred to the medium lacking it, there was an increase in the ascorbic acid content. Conversely, when material cultured on the nitrogenfree medium was suspended in the medium containing ammonium chloride, there •was a decrease in the celiuiar ascorbic acid. Exogenously added ascorbic acid, up to 0.5 mg per ml, increased the heterocyst frequency to nearly three times that of the control. D-isoascorbic acid, an analogue of ascorbic acid, also showed an enhancement of heterocyst production.Algal extracts were fractionated by poiyacrylamide electrophoresis, and the presence of ascorbic acid oxidase was detected on the gels. Two bands, with M values 0.J4 and 1.0, were found to give positive test for the enzyme. The total enzyme activity was 16.7 "/ty higher in cells grown with molecular nitrogen than in those gro'wn Tvith combined nitrogen. The exact location of tbe enzyme in the alga ist not known although the heterocysts were earlier shown to contain ascorbic acid. Cytochemical tests, however, indicated strong peroxidase activity in tbe heterocysts.

PlantL-ascorbic acid: chemistry, function, metabolism, bioavailability and effects of processing

“…Distinct from its effects on cell expansion, are reports on the influence of L‐AA on cell division and differentiation 41,101–103. Exogenous L‐AA has been found to accelerate the onset of cell proliferation in root primordia of Allium, Pisum and Lupinus ,42,97,104 due to an increased proportion of cells progressing through the G1/S transition 42,104–106.…”

Oxygen relations of nitrogen fixation in cyanobacteria.

“…Considering, however, that the affinity of ascorbate peroxidase for hydrogen peroxide is much higher than that of catalase, ascorbate peroxidase may be much more effective in protecting the cells from the toxic effects of hydrogen peroxide. Ascorbate peroxidase activity could be limited by low substrate concentration in vegetative cells but not in heterocysts, which maintain much higher concentrations of ascorbate (347).…”