Replication terminates at the terminus terc

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- Replication terminates at the Terminus (terC), triggering… Cytokinesis (about 20 Minutes in E. coli ) • Z Ring Formation - Composed of ~10,000 Tubulin-like Fts Z Molecules Fts Z = Filamentous temperature-sensitive Mutant Z - Zip A anchors the Z Ring in the Cell Membrane Zip A = Z-interacting protein, Anchor • Septum (L= hedgerow) Synthesizing Enzymes are assembled - Cell Membrane is pinched inward - Septum Formation separates Daughter Cells • Z-Ring constricts inward, pulling Septum Synthesizing Activity inward - The Septum consists of the Cell Wall and the Cell Membrane. • The Daughter Cells separate
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Growth of Bacteria Page 5 Population Growth: The Bacterial Growth Curve • It ʼ s inconvenient (and incredibly tedious) to follow individual Microbes - It ʼ s more convenient to follow Populations The Bacterial Growth Curve (In the Lab) • Batch Culture (Flasks containing 50 ml of Tryptone Broth) • Shaking Water Bath (37°C) • If the Growth of an in-vitro Population is plotted-out, the Result will be a characteristic Growth Curve with 4 distinct Phases: - Lag Phase • Period during which Bacteria adapt to their new Environment - Logarithmic Phase (Exponential Phase) • Period during which Bacteria undergo rapid Binary Fission - Stationary Phase (Stationary, as in sta nding in Pla ce) • Period during which Death Rate equals Growth Rate - Death Phase • Period during which Death Rate exceeds Growth Rate • Generation Time (also called Doubling Time) is the Interval between successive Binary Fissions - Generation Times are determined during Exponential Growth • Your Clan will receive ~5 ml of Exponential E. coli - You ʼ ll keep them Exponential (in the Shaking Water Bath) • You ʼ ll take a Spectrophotometer Reading every 10 Minutes - When the Light Absorption has doubled, your Culture has doubled E. coli can have a Generation Time as short as 20 Minutes This oft-quoted Figure is a bit Misleading. It ʼ s true that under Ideal Growth Conditions, E. coli can indeed divide every 20 Minutes. But Replication in E. coli takes approximately 40 Minutes. So E. coli that are dividing every 20 Minutes have multiple DNA Replication Forks i.e. Granddaughter Chromosome Replication begins before Daughter Chromosome Replication has finished. They can ʼ t do this for Long. A 40 Minute Generation Time is more Sustainable.
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