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Prokaryotes

Prokaryotes. A Quick Tour. Bacteria Video. Bacteria Video. Bacteria on the point of a pin. They are small. “Heat-loving” prokaryotes (a Nevada geyser basin-water temp=104 o C). They are found everywhere that there is life. The three domains of life. Classification schemes.

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Prokaryotes

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  1. Prokaryotes A Quick Tour

  2. Bacteria Video • Bacteria Video

  3. Bacteria on the point of a pin They are small

  4. “Heat-loving” prokaryotes (a Nevada geyser basin-water temp=104oC) They are found everywhere that there is life

  5. The three domains of life

  6. Classification schemes Classification schemes

  7. A Comparison of the Three Domains of Life

  8. Diversity of Form and Function

  9. The most common shapes of prokaryotes Rod Coccus Spiral

  10. Cell Surface (1) • Cell wall • Peptidoglycan(found only in eubacteria) • Gram stain • LPS (lipopolysaccharide) • Gram negative bacteria have an outer membrane containing LPS (endotoxin)

  11. Gram-positive and gram-negative bacteria

  12. Gram-positive and gram-negative bacteria

  13. Cell Surface (2) • Capsule • A gelatinous secretion of some prokaryotes which provides additional protection and helps them to adhere to surfaces and to form aggregates

  14. Cell Surface (3) • Pili • Surface appendages used for adherence to a host or surface. • Sex pilus provides means for transfer of DNA during conjugation

  15. Pili

  16. Motility (1) • Flagella • Rotate rather than whip • Thinner than eukaryotic flagella • Not covered by an extension of the plasma membrane

  17. Form and function of prokaryotic flagella

  18. Prokaryotic flagella

  19. Prokaryotic flagella

  20. Prokaryotic flagella (Bacillus)

  21. Motility (2) • Gliding • Some bacteria move by gliding through a layer of slimy chemicals secreted by the bacteria

  22. Motility (3) • Taxis • Movement toward (positive) or away from (negative) a stimulus • Phototaxis • Chemotaxis

  23. Genome • One double stranded circular chromosome • Chromosome is concentrated in a region of the cell called the Nucleoid region. • Very little protein is associated with the bacteria DNA • Plasmids- small rings of DNA having supplemental (nonessential) genes

  24. Growth, Reproduction, and Gene exchange (1) • Reproduction by binary fission (no mitosis/no meiosis) • Generation time is widely variable • Short generation times allow prokaryotic populations to adapt to rapidly changing environmental conditions. New mutations are screened by natural selection very rapidly

  25. Growth, Reproduction, and Gene exchange (2) • Endospores • A protective mechanism available to some Gram positive organisms to survive adverse environmental conditions. • Resistent to heat, dessication, chemicals • May remain dormant for years

  26. An anthrax endospore

  27. Endospores

  28. Growth, Reproduction, and Gene exchange (3) • Genetic recombination methods • Transformation • Transduction • Conjugation

  29. Prokaryote colonies in culture

  30. Bacterial and fungal colonies

  31. Nutrition and Metabolism (1) • Photoautotrophs • Chemoautotrophs • Photoheterotrophs • Chemoheterotrophs

  32. Major Nutritional Modes

  33. Nutrition and Metabolism (2)Chemoheterotrophs • Saprobes • Decomposers that absorb nutrients from dead organic material • Parasites • Absorb nutrients from living hosts

  34. Nutrition and Metabolism (3) • Nitrogen metabolism • Eukaryotes can only use nitrogen in certain forms to build proteins and nucleic acids. Prokaryotes can metabolize most nitrogen compounds • Nitrogen Fixation is Unique to certain prokaryotes and is the only mechanism that makes atmospheric nitrogen available to living things for incorporation into organic molecules

  35. Nutrition and Metabolism (4) • Oxygen and growth • Obligate aerobes • Require oxygen, use cellular respiration • Facultative anaerobes • Use oxygen when it is available, but in its absence can grow using fermentation • Obligate anaerobes • Poisoned by oxygen • Live by fermentation or anaerobic respiration

  36. Mini-tour of prokaryote groups

  37. Major groups of prokaryotes

  38. Domain Archaea • Cell walls lack peptidoglycan • Many inhabit the most extreme environments on earth • Methanogens • Use H2 to reduce CO2 to CH4 • Some are used as decomposers in sewage treatment • Extreme Halophiles • High salt environments (15-20%) • Extreme thermophiles

  39. Extreme halophiles Seawater evaporation ponds, used for commercial salt preparation. Colors are from growth of extreme halophiles. Salinity is 15-20%

  40. Hot springs, home of thermophiles

  41. Five of the Major Clades of Bacteria • Proteobacteria • Gram-positive bacteria • Cyanobacteria • Spirochetes • Chlamydias

  42. Cyanobacteria • Photoautotrophs with plantlike photosynthesis • Chloroplasts evolved from a cyanobacterium that lived as an endosymbiont within a larger host cell • Capable of Nitrogen Fixation

  43. One of the most independent organisms on earth: Cyanobacteria (Anabaena)

  44. Cyanobacteria: Gloeothece (top left), Nostoc (top right), Calothrix (bottom left), Fischerella (bottom right)

  45. A bloom of cyanobacteria

  46. Miscellaneous Topics (1) • Chemical cycles • Prokaryotes are critical links in the recycling of chemical elements between the biological and physical components of ecosystems (critical to the continuation of life) • Decomposers • Autotrophic bacteria

  47. Miscellaneous Topics (2) • Symbiosis • Ecological relationship between organisms of different species that are in direct contact. • Mutualism • Both organisms benefit • Commensalism • One organism benefits while neither helping or hurting the other • Parasitism • The parasite benefits at the expense of the host

  48. Miscellaneous Topics (3) • Disease • Opportunistic pathogens • Koch’s postulates • Find the same pathogen in each diseased individual • Isolate pathogen from a diseased subject and grow it in pure culture • Use the cultured pathogen to induce the disease in experimental animal • Re-isolate the same pathogen in the diseased experimental animals • Toxins • Exotoxins • Endotoxins

  49. Haemophilus influenzae on nasal mucosa

  50. Lyme disease, a bacterial disease transmitted by ticks

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