DIATOM MINERALIZATION OF SILICIC ACID. V. ENERGETIC AND MACROMOLECULAR REQUIREMENTS FOR Si(OH)4 MINERALIZATION EVENTS DURING THE CELL CYCLE OF NAVICULA PELLICULOSA1

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Abstract
The reactions and processes which underlie the silicification mechanism (incorporation of soluble pool Si into insoluble material) in the diatom Navicula pelliculosa (Bréb.) Hilse are quite sensitive to low temperature. Furthermore incorporation is completely blocked in 66Ge‐Si(OH)4 preloaded cells treated with an inhibitor of oxidative phosphorylation (2,4‐dinitrophenol) or a sulfhydryl blocking agent (N ‐ethylmaleimide). De novo protein synthesis is not required for incorporation in cells preloaded 3 h, but cycloheximide added to cells preloaded 1 h inhibits incorporation after 2 h. These results are interpreted to indicate that purely chemical reactions, which are uncoupled from cellular metabolism, cannot completely account for Si(OH)4 polycondensation during silica frustule morphogenesis in the diatom. A temperature sensitive cellular process or reaction, postcytokinesis, is also postulated to be required before silicification can occur.