ROLE OF SILICON IN DIATOM METABOLISM . A SILICON REQUIREMENT FOR DEOXYRIBONUCLEIC ACID SYNTHESIS IN DIATOM CYLINDROTHECA-FUSIFORMIS REIMANN AND LEWIN

Silicon deprivation of young cells of C. fusiformis in light-dark synchronized cultures completely inhibited mitosis without affecting normal increase in volume. During the first 12 h of silicon starvation, all major cell constituents, including ribonucleic acid, increased by at least 75%; deoxyribonucleic acid (DNA), however, increased by only 10%. Reintroduction of silicic acid to 12 h silicon-starved cells resulted in immediate stimulation of net DNA synthesis followed by mitosis, cytokinesis, cell wall formation and cell separation in 85% of the population. The cells were sensitive to inhibition of DNA synthesis during the first half of their division cycle. Approx. 50% of the silicon required for cell wall formation was sufficient to reverse the inhibition. Low concentrations of germanium inhibited mitosis and cell wall formation, but not DNA synthesis; high concentrations inhibited overall growth. © 1969.