The effect of potassium ion and light on the growth and ultrastructure of bracteacoccus cinnabarinus
Rentas, Angelo G.
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The green alga, Bracteacoccus cinnabarinus, was grown photoheterotrophically and heterotrophically with sodium acetate and potassium acetate as carbon-sources. The algae were also grown photoautotrophically. Using cells grown under all three conditions, the effects of potassium on the alga's macroscopic characteristics (e.g. cell size, color) were determined. The effects of potassium on the algal ultrastructure were studied with those cells grown photoautotrophically. It was also decided to determine if cells grown on medium containing acetate as the sole carbon-source could synthesize the glyoxylate cycle enzyme, isocitrate lyase. It was found that cells grown photoheterotrophically on potassium acetate were smaller and less colorful. This was not found to be true, however, of cells grown heterotrophically on potassium acetate. It was suggested that the combination of increased external potasium ion concentration and light induced transport of potassium ion into the cell leads to an internal potassium ion concentration inhibitory to the cell. Electron microscopy studies showed that cells grown photoautotrophically and photoheterotrophically on sodium acetate possess chloroplasts having normally stacked lamellae. Cells grown photoheterotrophically on potassium acetate, however, possessed chloroplasts whose lamellae were loosely stacked, appearing to have spread apart. It was suggested that this may have been caused by the increased external potassium ion concentration and the light induced transport of potassium ions and water into the intralamellar spaces. The increased influx of water and potassium ions into the intralamellar spaces could have led to an increased intralamellar volume and "spreading" of the chloroplast lamellae. That part of the study concerned with isocitrate lyase synthesis revealed that cells grown heterotrophically on sodium acetate do produce measurable quantities of the enzyme.