Prokaryotes: - PowerPoint PPT Presentation

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  1. Prokaryotes: Archaea & Bacteria

  2. The Tree of Life • All living things classified in three domains: • Bacteria • Archaea • Eukarya

  3. Amazing Living Things • Microbes indispensable to life: • Produce much of Earth’s: • Oxygen • Decomposition • Over half of Earth’s biomass • More bacterial cells than human cells in your body!

  4. Prokaryotes • Prokaryotes have: • Circular DNA, RNA, ribosomes, cytoplasm, plasma membrane • Most prokaryotes have a cell wall, a capsule (around the cell wall) and a flagellum • Prokaryotes don’t have: • Organelles such as nucleus, chloroplasts, mitochondria.

  5. Generalized Prokaryote Nucleoid DNA Plasmid DNA Cytosol Flagellum Capsule PlasmaMembrane Cell Wall

  6. Prokaryotic DNA • The area that contains the genetic material is referred to as the nucleoid. • The genes are usually in one continuous circular loop of DNA. • There may be other small circles of DNA outside the nulceoid called plasmids.

  7. Bacteria/Archaea • Habitats (name a place, and they live there!) • They are specialists • human skin, mouth, respiratory tract, large intestine, urogenital tract, etc. • salty Dead Sea • extreme pH • archea in deep sea vents: 90-106o C • Aerobes and anaerobes

  8. Some Prokaryotes Thrive in Extreme Conditions Cyanobacteria in Yellowstone Hot Springs

  9. Archaea • Unique lipid membranes, cell walls, and rRNA • Methanogens • Convert CO2 to methane • Swamps, hot springs, vent communities, cow stomachs • Halophiles - survive concentrated salt environment • Thermoacidophiles - thrive in hot, acidic environment • Generally in EXTREME environments

  10. Bacteria • Evolve Rapidly • Most of the time are asexual • Classified by shape, locomotion, pigments, nutrients, colonies

  11. Bacteria • Shape: • Cocci - round • Bacilli - rod • Spirilla - spirals

  12. (b) (c) Three Common Bacterial Shapes (a) bacillus cocci spirillus

  13. The Prokaryote Flagellum Flagella Bacterium

  14. Bacteria • Reproduction • Reproduction is asexual, by simple splitting (binary fission) • Daughter cells are genetic clones of the parent cell

  15. Binary Fission DNA

  16. Bacteria - Reproduction • Binary fission: • Very fast, up to once every 20 minutes • One bacterium-> 1021 in 24 hours. • Conjugation: (sexual reproduction) • Used only occasionally.

  17. Bacteria – Sexual Reproduction • Conjugation: • Genetic variation through pili (structures similar to flagella) and plasmid DNA • DNA is exchanged between bacterial cells • Occurs through a special large, hollow pilus • One bacterium acts as a donor, transferring DNA to the recipient.

  18. Conjugation Donor Recipient Sex Pilus

  19. Benefits of Bacteria • Symbiosis (mutualism) • Ruminants’ digestive tracts • Nitrogen fixing in soil, nodules on certain legumes • Bacteria on/in the human body: intestines and vitamin K and B12 • Biodegradation - oil • Food production - cheese, yogurt, sauerkraut • Decomposers

  20. Our Relationship With Bacteria

  21. Bacterial Pathogens • Some cause disease = pathogenic • In humans: • Strep throat • Toxins - tetanus, botulism • Pneumonia • "Flesh-eating" bacteria • Plague • Tuberculosis • Cholera • Lyme disease ANTIBIOTICS= anti bacterial!!!

  22. The Causes of Tooth Decay

  23. Transmission of Bacterial Pathogens • Airborne • Water • Food • Direct (skin contact, blood, and other body fluids) • Insect vectors and other hosts such as deer tick (Lyme) or mosquito.

  24. Germ Theory of Disease • Theory that microorganisms are the cause of disease. • 1859 – Louis Pasteur • Credited with the idea that human diseases were caused by bacteria and viruses (germ theory) • Very important discovery in the field of medicine

  25. Infectious Diseases • Average age of death, in first world countries, jumped 30+ years in last century due to antibiotics, and enhanced hygiene and nutrition. • Antibiotic-resistant infections on the rise in hospitals in the U.S. • This is due to bacterial evolution in response to widespread use of antibiotics!