1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 27 Prokaryotes

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: They’re (Almost) Everywhere! Most prokaryotes are microscopic – What they lack in size they more than make up for in numbers Number of prokaryotes in a single handful of fertile soil greater than the number of people who have ever lived

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Thrive almost everywhere – Places too acidic, too salty, too cold, or too hot for other organisms Figure 27.1

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Astonishing genetic diversity

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structural, functional, and genetic adaptations contribute to prokaryotic success Most unicellular although some species form colonies

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Variety of shapes 3 most common  spheres (cocci), rods (bacilli), and spirals 1  m 2  m 5  m (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral Figure 27.2a–c

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of cell wall is very important, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gram stain – classifies bacteria into two groups based on cell wall composition, Gram-positive and Gram- negative (a) Gram-positive. Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. The alcohol rinse does not remove the violet dye, which masks the added red dye. (b) Gram-negative. Gram-negative bacteria have less peptidoglycan, and it is located in a layer between the plasma membrane and an outer membrane. The violet dye is easily rinsed from the cytoplasm, and the cell appears pink or red after the red dye is added. Figure 27.3a, b Peptidoglycan layer Cell wall Plasma membrane Protein Gram- positive bacteria 20  m Outer membrane Peptidoglycan layer Plasma membrane Cell wall Lipopolysaccharide Protein Gram- negative bacteria

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell wall of many prokaryotes – covered by a capsule, a sticky layer of polysaccharide or protein 200 nm Capsule Figure 27.4

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some prokaryotes have fimbriae and pili – Which allow them to stick to their substrate or other individuals in a colony 200 nm Fimbriae Figure 27.5

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most motile bacteria propel w/ flagella – Structurally and functionally different from eukaryotic flagella Flagellum Filament Hook Cell wall Plasma membrane Basal apparatus 50 nm Figure 27.6

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many bacteria exhibit taxis – ability to move toward or away from certain stimuli

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells (most) – lack compartmentalization

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some prokaryotes – Do have specialized membranes that perform metabolic functions (a) Aerobic prokaryote(b) Photosynthetic prokaryote 0.2  m1  m Respiratory membrane Thylakoid membranes Figure 27.7a, b

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic genome – Ring of DNA, not surrounded by a membrane, located in a nucleoid region Figure 27.8 1  m Chromosome

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some also have plasmids

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproduce quickly by binary fission – And can divide every 20 min. – 3 hours

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many form endospores – Remain viable in harsh conditions for centuries Endospore 0.3  m Figure 27.9

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Rapid reproduction and horizontal gene transfer – Evolution of prokaryotes to changing environments

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diversity of nutritional and metabolic adaptations – Photoautotrophy – Chemoautotrophy – Photoheterotrophy – Chemoheterotrophy

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutritional modes Table 27.1

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolism w/ respect to O 2 Obligate aerobes – Require O 2 Facultative anaerobes – Can survive w/, w/o O 2 Obligate anaerobes – Poisoned by O 2

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen Metabolism e.g. nitrogen fixation – Convert atmospheric N 2 to ammonia

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooperation Cyanobacterium Anabaena – Photosynthetic cells and nitrogen-fixing cells exchange metabolic products Photosynthetic cells Heterocyst 20  m Figure 27.10

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A tentative phylogeny of some of the major taxa of prokaryotes based on molecular systematics Figure 27.12 Domain Bacteria Domain Archaea Domain Eukarya Alpha Beta Gamma Epsilon Delta Proteobacteria Chlamydias Spirochetes Cyanobacteria Gram-positive bacteria Korarchaeotes Euryarchaeotes Crenarchaeotes Nanoarchaeotes Eukaryotes Universal ancestor

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Proteobacteria Chromatium; the small globules are sulfur wastes (LM) Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Bdellovibrio bacteriophorus Attacking a larger bacterium (colorized TEM) 2.5  m 1  m 0.5  m 10  m 5  m 2  m Figure 27.13 Rhizobium (arrows) inside a root cell of a legume (TEM) Nitrosomonas (colorized TEM) Chromatium; the small globules are sulfur wastes (LM) Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Bdellovibrio bacteriophorus Attacking a larger bacterium (colorized TEM) Helicobacter pylori (colorized TEM).

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chlamydias, spirochetes, Gram-positive bacteria, and cyanobacteria Chlamydia (arrows) inside an animal cell (colorized TEM) Leptospira, a spirochete (colorized TEM) Streptomyces, the source of many antibiotics (colorized SEM) Two species of Oscillatoria, filamentous cyanobacteria (LM) Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM) 2.5  m 5  m 50  m 1  m Figure 27.13

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Domain: Archaea Archaea share certain traits with bacteria – And other traits with eukaryotes Table 27.2

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extreme thermophiles – Thrive in very hot environments

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extreme halophiles – Live in high saline environments Figure 27.14

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Methanogens – Live in swamps and marshes – Produce methane as a waste product

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes are so important to the biosphere that if they were to disappear – The prospects for any other life surviving would be dim

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Major role in recycling of elements between the living and nonliving components of ecosystems

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Decomposers – Break down corpses, dead vegetation, and waste products Nitrogen-fixers – Add usable nitrogen to the environment

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic Relationships e.g. mutualism and commensalism Figure 27.15

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some are parasites

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pathogenic Prokaryotes Prokaryotes cause ~1/2 human diseases – e.g. Lyme disease 5 µm Figure 27.16

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Typically cause disease by releasing exotoxins or endotoxins Some pathogenic bacteria are potential weapons of bioterrorism

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Experiments using prokaryotes – Have led to important advances in DNA technology

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bioremediation – Use of organisms to remove pollutants from the environment Figure 27.17

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Also major tools in – Mining – Synthesis of vitamins – Production of antibiotics, hormones, and other products