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Understanding Prokaryotes: The Essential Role of Bacteria and Archaea in Our World

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Prokaryotes, classified as Bacteria and Archaea, play an indispensable role in sustaining life on Earth. They are found in diverse environments, from human bodies to extreme places like the Dead Sea and hot springs. Prokaryotes lack organelles but possess unique structures and can thrive in varied conditions. Their rapid reproduction and unique processes like conjugation allow for genetic diversity. While many bacteria are beneficial, some are pathogenic. Understanding prokaryotes helps us appreciate their vital contributions, including oxygen production, decomposition, and human health.

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Understanding Prokaryotes: The Essential Role of Bacteria and Archaea in Our World

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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!

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