Evolution and Diversity of Prokaryotes

1. Chapter 16 0 The Origin and Evolution of Microbial Life: Prokaryotes and Protists

2. 0 How Ancient Bacteria Changed the World • Mounds of rock found near the Bahamas • Contain photosynthetic prokaryotes

3. Layers of a bacterial mat • Fossilized mats 2.5 billion years old mark a time when photosynthetic prokaryotes • Were producing enough O2 to make the atmosphere aerobic

4. EARLY EARTH AND THE ORIGIN OF LIFE • 16.1 Life began on a young Earth • Planet Earth formed some 4.6 billion years ago

5. The early atmosphere probably contained • H2O, CO, CO2, N2, and some CH4 • Volcanic activity, lightning, and UV radiation were intense Figure 16.1A

6. Fossilized prokaryotes called stromatolites • Date back 3.5 billion years Figure 16.1B

7. Ceno-zoic Meso-zoic Humans Paleozoic Land plants Origin of solarsystem andEarth Animals 4 1 Proterozoiceon Archaeaneon Multicellulareukaryotes years ago Billions of 3 2 Prokaryotes Single-celledeukaryotes Atmospheric oxygen • A clock analogy tracks the origin of the Earth to the present day • And shows some major events in the history of Earth and its life Figure 16.1C

8. 16.2 How did life originate? • Organic molecules • May have been formed abiotically in the conditions on early Earth

9. TALKING ABOUT SCIENCE • 16.3 Stanley Miller’s experiments showed that organic molecules could have arisen on a lifeless earth Figure 16.3A

10. “Atmosphere” CH4 Water vapor Electrode H2 NH3 Condenser Cold water Cooled watercontaining organic molecules H2O“Sea” Sample forchemical analysis • Simulations of such conditions • Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA Figure 16.3B

11. 16.4 The first polymers may have formed on hot rocks or clay • Organic polymers such as proteins and nucleic acids • May have polymerized on hot rocks

12. C A C U A A G G G A C G U G G A C U G U G C A A U U G U C U A U U A C G A 2 Assembly of a complementary RNAchain, the first step inreplication of the original “gene” G G C U C U U 1 Formation of short RNApolymers: simple “genes” Monomers • 16.5 The first genetic material and enzymes may both have been RNA • The first genes may have been RNA molecules • That catalyzed their own replication Figure 16.5

13. Self-replication of RNA RNA Self-replicating RNA acts astemplate on which poly-peptide forms. Polypeptide Polypeptide acts as primitive enzyme that aids RNA replication. • 16.6 Membrane-enclosed molecular cooperatives may have preceded the first cells • RNA might have acted as templates for the formation of polypeptides • Which in turn assisted in RNA replication Figure 16.6A

14. Membrane RNA Polypeptide LM 650 • Membranes may have separated various aggregates of self-replicating molecules • Which could be acted on by natural selection Figure 16.6B, C

15. Colorized SEM 650 PROKARYOTES • 16.7 Prokaryotes have inhabited Earth for billions of years • Prokaryotes are the oldest life-forms • And remain the most numerous and widespread organisms Figure 16.7

16. 16.8 Bacteria and archaea are the two main branches of prokaryotic evolution • Domains Bacteria and Archaea • Are distinguished on the basis of nucleotide sequences and other molecular and cellular features

17. Differences between Bacteria and Archaea Table 16.8

18. Colorized SEM 3,000 Colorized SEM 12,000 Colorized SEM 9,000 • 16.9 Prokaryotes come in a variety of shapes • Prokaryotes may be shaped as • Spheres (cocci) • Rods (bacilli) • Curves or spirals Figure 16.9A–C

19. 16.10 Various structural features contribute to the success of prokaryotes

20. Colorized TEM 70,000  Capsule • External Structures • The cell wall • Is one of the most important features of nearly all prokaryotes • Is covered by a sticky capsule Figure 16.10A

21. Pili Colorized TEM 16,000 • Some prokaryotes • Stick to their substrate with pili Figure 16.10B

22. Flagellum Colorized TEM 14,000 Plasmamembrane Cell wall Rotary movement ofeach flagellum • Motility • Many bacteria and archaea • Are equipped with flagella, which enable them to move Figure 16.10C

23. Reproduction and Adaptation • Prokaryotes • Have the potential to reproduce quickly in favorable environments

24. Endospore TEM 34,000 • Some prokaryotes can withstand harsh conditions • By forming endospores Figure 16.10D

25. Respiratorymembrane TEM 45,000 Thylakoidmembrane TEM 6,000 • Internal Organization • Some prokaryotic cells • Have specialized membranes that perform metabolic functions Figure 16.10E

26. 16.11 Prokaryotes obtain nourishment in a variety of ways • As a group • Prokaryotes exhibit much more nutritional diversity than eukaryotes

27. Types of Nutrition • Autotrophs make their own organic compounds from inorganic sources • Photoautotrophs harness sunlight for energy and use CO2 for carbon • Chemoautotrophs obtain energy from inorganic chemicals instead of sunlight

28. Heterotrophs obtain their carbon atoms from organic compounds • Photoheterotrophs can obtain energy from sunlight • Chemoheterotrophs are so diverse that almost any organic molecule can serve as food for some species Figure 16.11A

29. Nutritional classification of organisms Table 16.11

30. Colorized SEM 13,000 • Metabolic Cooperation • In some prokaryotes • Metabolic cooperation occurs in surface-coating colonies called biofilms Figure 16.11B

31. 16.12 Archaea thrive in extreme environments—and in other habitats • Archaea are common in • Salt lakes, acidic hot springs, deep-sea hydrothermal vents Figure 16.12A, B

32. Archaea are also a major life-form in the ocean

33. Colorized TEM 5,000 LM 13,000 • 16.13 Bacteria include a diverse assemblage of prokaryotes • Bacteria are currently organized into several subgroups, including • Proteobacteria Figure 16.13A, B

34. Chlamydias • Spirochetes

35. Nitrogen-fixingcells Colorized SEM 2,8000 Colorized SEM 2,800 LM 650 Photosyntheticcells • Gram-positive bacteria • Cyanobacteria, which photosynthesize in a plantlike way Figure 16.13C, D

36. Tick that carriesthe Lyme diseasebacterium SEM 2,800 Spirochetethat causesLyme disease SEM 12,000 “Bull’s-eye”rash CONNECTION • 16.14 Some bacteria cause disease • Pathogenic bacteria cause disease by producing • Exotoxins or endotoxins Figure 16.14A, B

37. CONNECTION • 16.15 Bacteria can be used as biological weapons • Bacteria, such as the species that causes anthrax • Can be used as biological weapons Figure 16.15

38. CONNECTION • 16.16 Prokaryotes help recycle chemicals and clean up the environment • Bioremediation • Is the use of organisms to clean up pollution

39. Rotatingspray arm Rock bed coated withaerobicbacteriaand fungi Outflow Liquid wastes • Prokaryotes are decomposers in • Sewage treatment and can clean up oil spills and toxic mine wastes Figure 16.16A, B

40. PROTISTS • 16.17 The eukaryotic cell probably originated as a community of prokaryotes • Eukaryotic cells • Evolved from prokaryotic cells more than 2 billion years ago

41. The nucleus and endomembrane system • Probably evolved from infoldings of the plasma membrane

42. Mitochondria and chloroplasts • Probably evolved from aerobic and photosynthetic endosymbionts, respectively

43. Cytoplasm Plasmamembrane Endoplasmicreticulum Nuclearenvelope Ancestral prokaryote Nucleus Membrane infolding Aerobic heterotrophicprokaryote Cell with nucleus andendomembrane system Somecells Photosyntheticprokaryote Ancestral host cell Endosymbiosis Mitochondrion Chloroplast Mitochondrion Photosyntheticeukaryotic cell • A model of the origin of eukaryotes Figure 16.17

44. LM 275 • 16.18 Protists are an extremely diverse assortment of eukaryotes • Protists • Are mostly unicellular eukaryotes • Molecular systematics • Is exploring eukaryotic phylogeny Figure 16.18

45. Fungi Ciliates Plants Diatoms Animals Amoebas Red algae Water molds Green algae Diplomonads Brown algae Apicomplexans Euglenozoans Dinoflagellates Choanoflagellates Cellular slime molds Plasmodial slime molds Closest algal relatives of plants Amoebozoa Alveolates Stramenopila Ancestral eukaryote • 16.19 A tentative phylogeny of eukaryotes includes multiple clades of protists • The taxonomy of protists • Is a work in progress Figure 16.19

46. Colorized SEM 4,000 • 16.20 Diplomonads and euglenozoans include some flagellated parasites • The parasitic Giardia • Is a diplomonad with highly reduced mitochondria Figure 16.20A

47. Colorized SEM 1,300 Colorized SEM 1,300 • Euglenozoans • Include trypanosomes and Euglena Figure 16.20B, C

48. SEM 2,300 • 16.21 Alveolates have sacs beneath the plasma membrane and include dinoflagellates, apicomplexans, and ciliates • Dinoflagellates • Are unicellular algae Figure 16.21A

49. TEM 26,000 Apex Red blood cell • Apicomplexans are parasites • Such as Plasmodium, which causes malaria Figure 16.21B

50. Cilia Macronucleus LM 60 • Cilliates • Use cilia to move and feed Figure 16.21C