Cellular changes during boron‐deficient culture of the diatom Cylindrotheca fusiformis

Abstract

The effects of boron‐deficient culture were studied on the unicellular diatom. Cylindrotheca fusiformis Reimann and Lewin. After 24 to 30 h, cell division was almost completely inhibited in boron‐deficient cultures. By 48 h of culture, boron‐deficient diatoms had approximately twice the modal cell volume of control cells, and at least twice the amount of organic constituents such as protein (2.0x), insoluble carbohydrate (2.4x), total phenols (2.6x), and chlorophyll at (2.1x). Boron deficiency led to irreversible damage after this time. Dark respiration was 1 nmol O2/min × 106 cells for both control and boron‐deficient diatoms prior to 40 h of culture. By 48 h, the respiratory rate of boron‐deficient diatoms was double that of controls. The proportion of 14C‐glucose metabolized by the pentose phosphate pathway was similar in both control and boron‐deficient diatoms after 24 and 48 h of culture. After 24 h, the in vitro activity of glucose‐6‐phosphate dehydrogenase was similar in both control and boron‐deficient cells, although the pool size of its substrate, glucose‐6‐phosphate, was 26% greater in boron‐deficient cells. The cellular amount of glucose‐6‐phosphate dehydrogenase continued to increase once mitosis was arrested in boron‐deficient diatoms. Boric acid (1 mM) inhibited 6‐phosphogluconate dehydrogenase by 18% in diatom homogenates. During the early stages of boron deficiency, the uptake of silicate, nitrate, and phosphate, and the in vitro activity of β‐glucosidase were similar to control diatoms. After cell division was inhibited, boron‐deficient diatoms accumulated more nitrate and phosphate, and retained a higher level of β‐glucosidase than control cells.

Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119

“…Smyth and Dugger (21), using the diatom Cylindroteca fusiformis, explained this accumulation by photosynthetic enhancement in B-deficient cultures. This explanation is not valid in Anabaena.…”

Boron-Dependent Degradation ofNIP5;1mRNA for Acclimation to Excess Boron Conditions inArabidopsis

“…Since then, B was shown to be essential for diatoms (Smyth and Dugger, 1981) and cyanobacteria (Bonilla et al, 1990) as well as for animals, including zebra fish (Danio rerio) (Rowe and Eckhert, 1999), trout (Oncorhynchus mykiss) (Eckhert, 1998;Rowe et al, 1998), frogs (Xenopus laevis) (Fort et al, 1998), and mice (Mus musculus) (Lanoue et al, 2000). Although the precise physiological role of B has not been established, it is beneficial for human health (Nielsen, 2000).…”

Importance of extracellular organic carbon production in the total primary production by tidal-flat diatoms in comparison to phytoplankton

“…The algal cells (POC fraction), which were disrupted by a sonic probe, and the supernatants (Colloidal-OC fraction), which were extracted with EDTA solution, were assayed for presence of the intracellular enzyme glucose-6-phosphate dehydrogenase (GGPD, EC 1.1.1.49) activity using the method of Smyth & Dugger (1981), to determine the extent of contamination of the extraceilular polymer by intracellular material. Protein in the algal cells and the supernatant was measured by the method of Smyth & Dugger (1981) and the Bradford method (Bradford 1976).…”