Role of silicon in diatom metabolism. V. Silicic acid transport and metabolism in the heterotrophic diatom Nitzschia alba.

摘要: 1. In the heterotrophic diatom, Nitzschia alba, 31Si(OH)4 appears to be transported by a carrier-mediated membrane transport system which conforms Michaelis-Menten type saturation kinetics with Ks of 4.5×10-6M and Vmax 3.35 gmmoles/g wet wt/min at 30°C. A Q10 2.0 was calculated from rates silicic acid uptake 20°C Calculations same data showed that energy activation for is 12.1 Kcal/mole. Optimum pH broad, ranging between 6 9. 2. During pulse-labelling 31Si(OH)4, label increases in cytoplasm more rapidly than cell wall, indicating build-up cytoplasmic pool or its derivatives, suggesting possible chemical transformation cytoplasm. The concentration 31Si reaches 30 40 times external concentration, but accumulated does not flow out into Si-free medium exchange non-radioative Si(OH)4. 3. The metabolic inhibitors DNP, CCCP, iodoacetamide, azide, antimycin strongly inhibit 90–97%, whereas ionophorous compounds, nigericin valinomycin, have no effect. 4. Inhibition protein synthesis cycloheximide inhibits 50–70%. 5. Germanic acid, an inhibitor diatom growth, uptake; Ki 2.2×10-6. 6. Sub-cellular fractionation cells exposed 10 min 90% wall; remaining 10% distributed various fractions including “soluble fraction”. 7. The demonstrate required net N. alba cells, suggest active may involved. role nature are discussed.