Centric diaton 1 n 10 rphogenesis : a 1110 del based 011 a DLA algorith 111 investigating the potential role of l 11 icrotubules

Diatoms are single-celled algae which possess characteristic rigid cell walls (frustules) composed of amorphous silica. Frustule formation occurs within a specialised organelle termed thc silica deposition vesicle (SOY). During diatom morphogenesis, silica particles arc transported to the SOY by silica transport vesicles, Once released within the SOY, the particles are then thought to diffuse until they encounter part of the growing aggregate upon which they adhere. The particles may then undergo a further period of surface relocalisation (sintering) which leads to a smoothing of the surface. A number of computer simulations based on a modified diffusion-limited aggregation (OLA) algorithm, have been undertaken to investigate the potential role of micro tubules (which arc known to be associated with the periphery of the SOY) in localising deposition of new siliceous material. Based on our findings, we present a new model of diatom morphogenesis which is able to account for many morphological features of diatoms including the influence of environmental effects such as changes in pH and salinity, and the formation of a regular branched pattern. .f;;) 1999 Elsevier Science B.Y. All rights reserved.