17 Prokaryotes I - Lecture 17 Monera Historical...

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Lecture 17: Monera April 26, 2007
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Carl Linnaeus 1707-1778 Historical classifications 3 kingdoms were recognized: 1- Animalia: Organism that moved and ate, grow and eventually stopped growing. 2- Plantae: Organisms that did not move, or eat but grew indefinitely 3- Minerals
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Evolutionary tree Prokaryote called true bacteria Prokaryotes capable of living in extremes Include all eukaryotes At the molecular level Bacteria and Archaea are distinct from each other and from eukaryotes.
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Genome sequence Over 100 prokaryotic genomes are sequenced and the results support presence of 3 domains of life.
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Prokaryotes Structurally simplest and physically smallest and most abundant organisms. Total weight exceeds that of other organisms. One gram of soil contains 2.5 billion individuals. Evolutionarily oldest organisms and most successful form of life. Prokaryotes capable of living in environment that supports no other form of life
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3.5 billion years old fossil of prokaryotes
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Thermophilic prokaryotes Hot spring in Yellowstone park
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Why are prokaryotes so successful? 1- Metabolic diversity 2- Rapid division ( E. coli double in size /20 min) 3- Adaptability Question Molecular mechanism responsible for their adaptability?
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Prokaryotes are metabolically diverse 1- Autotroph (self feeding) A: Photosynthetic autotroph B: Chemosynthetic autotroph Sulfur oxidizing bacteria, cells are filled with sulfur particles found in polluted waters and sulfur spring
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Prokaryotes are metabolically diverse 2- Heterotrophs Requiring organic compounds as a carbon source. Majority are saprophytic Important decomposers in the environment
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Why are prokaryotes important? 1- Autotrophic bacteria are major contributors to carbon balance 2- Nitrogen fixation 3- Producers of 90% of CO2 4- Biological decomposers 5- Source of antibiotics 6- Commercial use for production of amino acids & enzymes 7- Food industry 8- potent disease causing agents
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Nitrogen fixing bacteria Anabaena lives in the water fern in the paddies Growing rice without a fertilizer
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Characteristics of prokaryotic cells Lack of organized nucleus bounded by nuclear envelop Circular DNA in a region of cells called nucleoid. In addition to chromosomal DNA they may contain extra chromosomal circular DNA called plasmids that replicate independent from cells chromosomes. Cytoplasm contains as many as 10,000 ribosomes. These cytoplasmic ribosomes are smaller in size (70S) than those of eukaryotes (80S) .
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