Lecture 15 Microbes

Lecture 15 Microbes - ANNOUNCEMENTS Wednesday, March 10th...

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ANNOUNCEMENTS – Wednesday, March 10th Final Exam will be comprehensive; I’ve posted an old midterm from a previous year to provide a good idea of what to expect. Final Exam Review Session: Saturday, March 13 th from 5-7 PM in CENTER 115. Final Exam also here in CENTER 115, 7-10 PM, Monday March 15 th . PS5 Key now posted on website. Regrades available after class. I would greatly appreciate your feedback via CAPE. Lecture 15 Bacteria and Viruses Microbial Systems: Viruses & Bacteria -“ model systems” reveal broad principles - unique systems in pathogenesis 0.5 μ m E. coli bacterium Bacteriophage viruses Relative size of microbes Why study bacteria? 1. DNA technology (E. coli is a “micro-factory”) 2. Clinical (and war) importance (anthrax) 3. Study of evolution (mutation rate) Bacterium Virus Animal cell
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Why Study Bacteria: Evolutionary Study from Bacteria Takaaki Sato, Haruyuki Atomi, Tadayuki Imanaka “Archaeal Type III RuBisCOs Function in a Pathway for AMP Metabolism” Science, Vol 315, page 1003, 16 February 2007 In plants and other photosynthetic organisms, rubisco functions to ±x carbons during Calvin Cycle in photosynthesis. In T. kodakaraensis (a non- photosynthetic archaeal bacterium), rubisco is found to function in glycolysis. Thus, before photosynthesis occurred on Earth, rubisco was just another protein in sugar metabolism. A prokaryotic cell Pili: attachment structures Nucleoid and chromosome: Not enclosed by a membrane Plasma membrane Cell wall and capsule: structural support Flagella: locomotion organelle (a) A typical rod-shaped bacterium (b) TEM result 0.5 μm Microbial Systems: E. Coli infection of human intestine - Simplest true organism - Rapid asexual reproduction by binary fission (~20 min.) - results in clonal growth - Mutation - spontaneous mutations w/high reproduction rate - genetic recombination - Bacterial sex: gene transfer and genetic recombination Genetic Diversity of Bacteria The “lab rat” of molecular biology
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Chromosome – usually a single circular dsDNA molecule (~4000 genes) Plasmids – small circular DNA molecules – replicate independently of chromosome – found in many bacteria The Bacterial Genome BFP, mTFP1, Emerald, Citrine, mOrange, mApple, mCherry and mGrape Artwork by Nathan Shaner, photography by Paul Steinbach, created in the lab of Roger Tsien in 2006 Mutant strain arg - trp + Only mixed samples gave rise to colonies on medium lacking amino acids. Mutant strain arg + trp Mixture could make arginine but not tryptophan could make tryptophan but not arginine Genetic Diversity from Recombination Colonies grew Bacterial Sex: Mechanisms of Gene Transfer 3 different processes bring together bacterial DNA from different individuals: 1. Transformation 2. Transduction 3. Conjugation
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Alteration of a bacterial cell’s genotype and phenotype by the uptake of naked, foreign DNA from the surrounding environment. Bacterial Gene Transfer:
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Lecture 15 Microbes - ANNOUNCEMENTS Wednesday, March 10th...

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