Lecture 12, Ch. 27

Lecture #12

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Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity

Classification ● ● ●

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Kingdom: Monera? Domain: Bacteria Domain: Archaea

Shape •cocci (sphere) •bacilli (rod) •helical (spiral)

Structural characteristics ●

Cell wall~ peptidoglycan (sugars & proteins); √ Gram +: w/peptidoglycan penicillin action √ Gram -: little peptidoglycan, lipopolysaccharides; most pathogens; impede drug action

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Capsule: adherence; protection Pili: adherence; conjugation

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Motility ● ●

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1- Flagella 2- Helical shape (spirochetes) 3- Slime 4-Taxis (movement away or toward a stimulus)

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Form & Function ●

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Nucleoid region (genophore: non-eukaryotic chromosome) Plasmids Asexual reproduction: binary fission (not mitosis) “Sexual” reproduction (not meiosis): transformation~ uptake of genes from surrounding environment conjugation~ direct gene transfer from 1 prokaryote to another transduction~ gene transfer by viruses Endospore: resistant cells for harsh conditions (250 million years!)

Nutrition & Metabolism ●

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Photoautotrophs: photosynthetic; harness light to drive the synthesis of organics (cyanobacteria) Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO2 Photoheterotrophs: use light to generate ATP but get carbon in an organic form Chemoheterotrophs: consume organic molecules for both energy and carbon saprobes- dead organic matter decomposers parasites- absorb nutrients from living hosts Nitrogen fixation: conversion of atmospheric nitrogen (N2) to ammonium (NH4+) Oxygen relationships: obligate aerobes; facultative anaerobes; obligate anaerobes

Prokaryotic ecology ●

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Decomposers: unlock organics from corpses and waste products Symbiosis~ •symbiont/host •mutualism (+, +) •parasitism (+, -) •commensalism (+, 0) Disease •opportunistic: normal residents of host; cause illness when defenses are weakened •Koch’s postulates: criteria for bacterial disease confirmation •exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) •endotoxins: components of gram membranes (Salmonella)