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Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity

Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity. Classification. Domain: Bacteria Found almost everywhere Domain: Archaea Usually found in extreme environments. Structure of Bacteria. Shape cocci (sphere) Can be alone or in colonies bacilli (rod)

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Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity

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  1. Chapter 27~ Prokaryotes and the Origins of Metabolic Diversity

  2. Classification • Domain: Bacteria • Found almost everywhere • Domain: Archaea • Usually found in extreme environments

  3. Structure of Bacteria • Shape • cocci (sphere) • Can be alone or in colonies • bacilli (rod) • Usually solitary but can be in chains • helical (spiral) • Corkscrew shape

  4. Structural characteristics • Almost all prokaryotes have a Cell wall • Made of peptidoglycan (sugars & proteins) • Gram +: large amount of peptidoglycan outside of membrane • Gram -: little peptidoglycan in between two membranes- outer one has lipopolysaccharides • Usually more harmful and resistant to drugs than gram + • Capsule: adherence and additional protection • Pili: adherence and conjugation

  5. Motility • Flagella • Helical shape (spirochetes) • Slime • Taxis • movement away or toward a stimulus

  6. Form & Function • 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: makes cell resistant in harsh conditions (250 million years)

  7. Prokaryotic Growth • Conditions for growth vary with species • cold conditions ( refrigerator) slow growth • Most have generations times of 1-3 hours but some can divide every 20 minutes • Statistic • 1 cell could give rise to a colony weighing 1 million kg in 24 hrs if no limits on growth!!!!! • Equals 2.2 million pounds in 24hrs!

  8. Nutrition & Metabolism • Photoautotrophs: photosynthetic; harness light to drive the synthesis of organic compounds (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

  9. Nutrition & Metabolism • Oxygen relationships: • Obligate aerobes • Use O2 for cell. resp. and cannot live with out it • Facultative anaerobes • Will use O2 if present but can grow by fermentation in anaerobic environments • Obligate anaerobes • Poisoned by O2

  10. Domain Archea Bacteria • 3 main groups • Methanogens • Give off methane, anerobes, live in swamps and marshes where O2 is low, give off methane gas • Halophiles • Live in saline places like great salt lake • Extreme thermophiles • Hot environments, deep sea vents

  11. Domain Bacteria • 5 Major groups ( see pg 514 of book)

  12. Prokaryotic ecology • Decomposers: unlock organics from corpses and waste products • Symbiosis: • Symbionts ( organisms involed in relationship) / host • mutualism (+, +) • Rhizobium and legumes • parasitism (+, -) • Bacteria that cause illness • commensalism (+, 0) • Bacteria in human body

  13. Prokaryotes and Disease Opportunistic: normal residents of host; cause illness when defenses are weakened Ex. Streptococcuespneumoniae • Exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) • Endotoxins: components of gram - membranes (Salmonella)

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