1. BC35F: Biotechnology of Industrial Ethanol Production Saccharomyces cerevisiae Cell Biology and Biochemistry 1 (Continued)

2. S. cerevisiae cell wall properties: Flocculation vs Buoyancy (flotation) Flocculation:phenomenon of asexual cellular aggregation in which cells adhere reversibly to form marcoscopic flocs, which sediment out of suspension. Bottom yeasts (lager beers) flocculate Top yeasts (ales) are buoyant BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)

4. S. cerevisiae cell wall properties: Flocculation:brought about by flocculins:cell surface glycoproteins which bind to cell surface mannoproteins, similar in action to lectins. Agglomeration: irreversible aggregation, giving rise to baking industry problems with dough leavening: “grit” or “sand”. BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)

5. Sporulation:spore-formation induced in S. cerevisiae by N-deprivation and supplying acetate as respiratory substrate. Meiosis occurs and a four-lobed nucleus forms, which gives rise to 4 spores. BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)

8. Genome.Now complete sequence available. Dr Ashby will discuss further. Extrachromosomal DNA: Mitochondrial (say no more!) 2  m DNA: ~60 copies of circular, histone-covered plasmids of unknown function; useful as cloning vectors. “Killer” plasmids: dsRNA encoding toxins to kill sensitive strains 20s, 23s RNA: naked circular ssRNAs BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)

9. Mitochondria One, few or several? Not sure: BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)

10. Vacuole.One or few? Isolated or linked to E.R? Not sure. Functions:Protein turnover/trafficking Control of [Trehalose] intracellular pH control Storage of most nutrients: polyphosphate, basic amino acids, metal ions; uptake by proton antiport. BC35F: Lecture 1 Cell Biology of S. cerevisiae (continued)