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L.02. Growth of Bacteria

In 1951 esther lederberg demonstrated that e coli

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- In 1951 Esther Lederberg demonstrated that E. coli could be infected with a Temperate Bacteriophage named Lambda Phage (Luck). Temperate Bacteriophage (Bacterial Viruses) can integrate their DNA into the Host Cell Genome, mysteriously “disappear” for several Generations , and then excise themselves and subsequently lyse the Host Cell. - In 1952 Joshua Lederberg (Esther ʼ s Husband) demonstrated Sex in E. coli (Luck). The Discovery that Bacteria could have Sex was almost as amaziating as the Discovery that Bacteria obeyed the Laws of Mendelian Genetics. - In 1955 François Jacob used a Waring Blender to interrupt E. coli Matings to generate the first Map of a Bacterial Chromosome (Choice). Their “Coitus interruptus” Experiments were rude, crude and convincing. - In 1958 Matthew Meselson and Franklin Stahl demonstrated that DNA Replication in E. coli was indeed Semi-Conservative (Choice). Theirs was the first Genetic Proof of the Double Helix Theory. - During the 1950s François Jacob and Jacques Monod dissected the Lactose Operon in E. coli and the surprisingly similar Operon Lambda Phage uses to regulate its Replication (Choice). • So by the End of the 1950s E. coli had become the Organism of Choice for Bacterial Genetics and Molecular Biology.
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Growth of Bacteria Page 4 Individual Growth: The Cell Cycle in Bacteria Bacteria reproduce by Binary Fission (G= split into two) Chromosomal Replication (about 40 Minutes in E. coli ) • The Origin (oriC) and the Terminus (terC) on the Chromosome move to the Middle of the Cell -The Proteins needed for Chromosome Replication assemble to form a Replisome (Repli cation + G= body) • Chromosome Replication - Replication begins at the Origin (oriC) Replication is Bi-Directional (i.e. occurs in both Directions from the Origin) - Cell Elongation begins as Chromosome Replication begins • New Origins are moved toward opposite Poles of the Cell E. coli has at least 7 Enzymes termed Penicillin-Binding Proteins (PBP1a, PBP1b, PBP2, PBP3, PBP4, PBP5 and PBP6), which were first identified because Penicillin binds to them. It took a while for their Function to be discovered. Peptidoglycan Synthesis occurs until the Cell is approximately double its normal Length.
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