Bipolar budding in yeasts - an electron microscope study

Bud formation in yeasts with bipolar budding was studied by electron microscopy of thin sections. Budding in yeasts of the species Saccharomycodes ludwigii, Hanseniaspora valbyensis and Wickerhamia fluorescens resulted in concentric rings of scar ridges on the wall of the mother cell. The wall between the ridges consisted of the scar plug left by the former budding and opened up in the formation of the next bud. The wall of the bud arose from under the wall of the mother cell. In the yeasts of the species Nadsonia elongata more than one bud might be formed from the same plug. In Schizoblastosporion starkeyi-henricii the scar ridges were close together and apparently not separated by the entire plug. In all species a cross wall was formed between mother cell and bud which consisted of an electron-light layer between two layers of more electron-dense material. The cells separated along the light layer