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Welcome to Biology 213

Welcome to Biology 213. Into the Prokaryotes!. The History of Life. Organizing Life As We Know It Today. Robert Whittaker, 1969. Carl Woese’s Tree Based on ssuRNA Sequence Analysis!. Organizing Life: The Debate. Our tour begins with the prokaryotic kingdoms/domains….

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Welcome to Biology 213

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  1. Welcome to Biology 213 Into the Prokaryotes!

  2. The History of Life

  3. Organizing Life As We Know It Today Robert Whittaker, 1969

  4. Carl Woese’s Tree Based on ssuRNA Sequence Analysis!

  5. Organizing Life: The Debate Our tour begins with the prokaryotic kingdoms/domains…

  6. "The key to taking the measure of biodiversity lies in a downward adjustment of scale. The smaller the organism, the broader the frontier and the deeper the unmapped terrain...... A lifetime can be spent in a Magellanic voyage around the trunk of a single tree." -(E. O. Wilson, 1995)

  7. The Prokaryotes: Characteristics Source: www.agen.ufl.edu/~chyn/age2062/ lect/lect_06/lect_06.htm

  8. The Prokaryotes: Characteristics • No membrane-bound nucleus • Single chromosome (+plasmids) • Typically have a Cell Wall • Reproduction by prokaryotic fission • Enormous metabolic diversity! Source: micro.magnet.fsu.edu/cells/ bacteriacell.html

  9. Prokaryotic Cell Walls

  10. Many Prokaryotes have Capsules outside the cell wall Capsules have a role in adherence, virulence, protection, securing nutrients, and cell-to-cell recognition.   Capsule-producing bacillus-shaped bacteria.

  11. Many Prokaryotes also have surface appendages called PILI • Prokaryotes such as this E coli, strain 0157:H7 use pili to adhere to one another or to a surface

  12. Many Prokaryotes are MotileMechanism 1 = Flagella Analogous to Eukaryotic Flagella! Chains of Flagellin

  13. Many Prokaryotes are MotileMechanism 2 = Helical FilamentsMechanism 3 = “Slimy Threads” Spirochetes: A. Cross section of a spirochete showing the location of endoflagella between the inner membrane and outer sheath; B. Borrelia burgdorferi, the agent of Lyme disease; C. Treponema pallidum, the spirochete that causes syphilis.Source:www.bact.wisc.edu/Bact303/ MajorGroupsOfProkaryotes

  14. Many Prokaryotes are Motile This results in taxis, or the movement towards or away from a stimulus. Many prokaryotes can move directionally along gradients of light, chemicals, or even magnetic fields!

  15. Prokaryotes can be distinguished by SHAPE The three most common shapes: Rod-shaped bacilli Spherical Cocci Helical Spirillum Prokaryotes that clump together = staphylo- Prokaryotes that form chains = strepto-

  16. The Prokaryotes: Characteristics Ubiquitous! Bacteria can be found virtually anywhere, including in dental plaque (left) and on the surface of a contact lens (right). Courtesy MicrobeLibrary.org

  17. The Prokaryotes: Characteristics • Abundant! A single teaspoon of topsoil contains about a billion bacterial cells (and about 120,000 fungal cells and some 25,000 algal cells). The human mouth is home to more than 500 species of bacteria. Source: www.microbeworld.org Nitrifying bacteria cross sectionPhoto credit: Mary Ann Bruns, Center for Microbial Ecology, Michigan State University

  18. The Prokaryotes: Characteristics Prokaryotes reproduce rapidly through binary fission

  19. The Prokaryotes: Characteristics Prokaryotes reproduce asexually, but still exchange genetic information via transformation, conjugation, and transduction Mutation is also a very important source of genetic variation in prokaryotes!

  20. The Prokaryotes: Characteristics Some prokaryotes can form resistant cells called ENDOSPORES The chromosome is replicated and becomes encased in an extremely durable wall

  21. Terms to Describe Metabolic Diversity Categorize prokaryotes according to how the acquire ENERGY and a CARBON SOURCE Can use LIGHT = PHOTOTROPHS or CHEMICALS = CHEMOTROPHS Need only CO2 = AUTOTROPHS or Need 1+ ORGANIC NUTRIENTS = HETEROTROPHS

  22. Example: An Alternate Strategy How would I describe a bacteria that could do this??

  23. Most Prokaryotes are CHEMOHETEROTROPHS Can be either SAPROBES- absorb nutrients from dead organic matter or PARASITES- absorb nutrients from living hosts

  24. Chemoheterotrophic Prokaryotes Utilize a Diverse Assortment of Organic Nutrients Some prokaryotes utilize very specific media; Some, such as E. coli, can utilize a variety of carbon sources Lactobacillus

  25. Relationships with Oxygen • Obligate Aerobes (cannot live without O2) • Facultative Aerobes (use O2 if present, but can do fermentation) • Obligate Anaerobes (poisoned by oxygen!)

  26. Nitrogen Metabolism Fixation = N2 NH3 (ammonia)

  27. Many Prokaryotes Process Nitrogen 1. Denitrification- nitrite (NO2) or nitrate (NO3-) converted to Nitrogen Gas (N2) 2. Nitrogen Fixation- convert atmospheric nitrogen (N2) to ammonium (NH4+) Anabaena

  28. This Enormous Diversity of Strategies Probably Evolved Early Earliest Strategy?

  29. This Enormous Diversity of Strategies Probably Evolved Early Probably heterotrophic… Glycolysis! Natural Selection would eventually favor photosynthesis

  30. The Archaea

  31. Prokaryotes: the Archae • Thermophiles like unusually hot temperatures. A few species have been found to survive even above 110 degrees Celsius (water boils at 100 degrees Celsius). • Psychrophiles like extremely cold temperatures (even down to -10 degrees Celsius). • Halophiles thrive in unusually salty habitats. Some can thrive in water that’s 9% salt; sea water contains only 0.9% salt. • Acidophiles prefer acidic conditions; Alkaliphiles prefer very alkaline environs. Source: www.microbeworld.org

  32. Prokaryotes: the Archae • Methanogens use CO2 to oxidize H2, producing methane as a waste product. Methanogens are strict anaerobes! This appears to be a monophyletic group that evolved very early.

  33. Prokaryotes: the Archae • No peptidoglycan in their cell walls • Use multiple RNA Polymerases • Some of their genes have introns • They are not affected by antibiotics • They use histones to organize their DNA Do these seem like prokaryotic or eukaryotic traits?? Is this consistent with what we’ve learned from rRNA?

  34. The “Bacteria”

  35. The Proteobacteria • Gram negative • Diverse: photoautotrophs, chemoautotrophs, heterotrophs, may be anaerobic or aerobic • Five subgroups fall out: Alpha, Beta, Gamma, Delta, and EpsilonProteobacteria

  36. The Alpha Proteobacteria • Most symbiotic/parasitic • Mitochondria evolved from aerobic alphas! • Famous Alphas include: Nitrogen fixing symbionts, the plant pathogen Agrobacterium, and Rocky Mountain Spotted fever Alfalfa (Medicago sativa) S. meliloti cells SEM courtesy of William Margolin.

  37. The Beta Proteobacteria • Diverse group, includes Nitrosomonas. Nitrosomasconverts ammonium to nitrite • Also includes Thiobacillus, the sulfur and iron oxidizing bacteria (obligate chemoautotrophs, using inorganic compounds as electron donors and carbon dioxide as the carbon source)

  38. The Beta Proteobacteria More famous Beta Proteobacteria: • Bordetella pertussis • Neisseria meningitidis. Causes meningococcal meningitis • Neisseria gonorrhoeae. Causes gonorrhea, one of the most common sexually-transmitted diseases (STDs): 355,642 cases in the U.S. in 1998

  39. The Gamma Proteobacteria • Diverse group including photosynthetic sulfur bacteria • Famous heterotrophic members include: Legionella, Salmonella, Vibriocholerae,Escherichia coli, and Yersiniapestis Buboes are a symptom of the bubonic plague. (Photo courtesy Jose Quintas - University of Chicago)

  40. The Delta Proteobacteria • Include the very elaborate myxobacteria- soil bacteria that secrete a slimy substratum and produce fruiting bodies when conditions become poor • Also includes bacterial predators, the bdellovibrios

  41. The Epsilon Proteobacteria • Closely related to the deltas • Includes Helicobacter pylori (stomach ulcers) and Campylobacter jejuni (the bacterium most frequently implicated in gastrointestinal upsets) Scanning electron microscope image of Campylobacter jejuni, illustrating its corkscrew appearance and bipolar flagella. Source: Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia.

  42. The “Bacteria”

  43. The Chlamydias • All parasitic, living inside animal cells (dependent on host for ATP) • Gram-negative and lack peptidoglycan in their cell walls • Famous Chlamydias: Chlamydia trachomatis causes blindness and nongonococcalurethritis (most common STD in the US) Scanning electron micrograph of a chlamydia inclusion body leaving a host cell in a dramatic fashion. The inset shows a closeup of the elementary bodies breaking free of the inclusion body. Source: CDC

  44. The Spirochetes • Long Cells (0.25mm!), uses internal filament to produce corkscrew-like movement • Famous spirochetes include: Treponemapallidum (syphilis) and Borreliaburgdorferi (Lyme disease) Source: dev.triothinkquest.org

  45. The Gram-Positive Bacteria • All gram-positive and a few gram negative • Includes the actinomycetes (tuberculosis, leprosy, + Streptomyces) • Also includes solitary species (Bacillus, Staphylococcus, Streptococcus)

  46. Another Unusual “Gram +” Electron micrograph of thin-sectioned mycoplasma cells. Cells are bounded by a single membrane. (Photo: RM Cole, Bethesda, Maryland).

  47. The “Bacteria”

  48. The Cyanobacteria • Only prokaryotes with oxygenic photosynthesis (early endosymbionts?) • Solitary or colonial in aquatic environments • Some filamentous forms can fix nitrogen

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