Combined sem ultrastructure studies and PCR with individual diatom cells

Perforation of frustules of individual cells of the diatom Aulacoseira skvo rtzowii Edlund, Stoermer & Taylor with an extended glass needle controlled by a micro-manipulator was used to liberate the protoplast. The isolated to tal DNA was used in subsequent amplification with specific primers and sequ encing of a fragment of the rbcL gene. Comparison of the sequence of the am plified rbcL gene fragment from A. skvortzowii, with those known for other plants, revealed that it is closest to the sequence of rbcL from the marine diatom Skeletonema costatum (12 amino acid substitutions over a fragment o f 130 amino acid residues). Features of the ultra-structure of A. skvortzow ii that are important for species identification (form and density of areol ae, form of suture spine, etc.) remained intact when using this technique. The combined approach promises a breakthrough in the application of DNA seq uencing to diatom research.