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CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole.

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Presentation on theme: "CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole."— Presentation transcript:

1 CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 24 Early Life and the Diversification of Prokaryotes

2 © 2014 Pearson Education, Inc.  Earth formed 4.6 billion years ago  The oldest fossil organisms are prokaryotes dating back to 3.5 billion years ago  Prokaryotes are single-celled organisms in the domains Bacteria and Archaea  Some of the earliest prokaryotic cells lived in dense mats that resembled stepping stones Overview: The First Cells

3 © 2014 Pearson Education, Inc. Figure 24.1

4 © 2014 Pearson Education, Inc.  Prokaryotes are the most abundant organisms on Earth  There are more in a handful of fertile soil than the number of people who have ever lived  Prokaryotes thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms  Some prokaryotes colonize the bodies of other organisms

5 © 2014 Pearson Education, Inc. Figure 24.2

6 © 2014 Pearson Education, Inc. Concept 24.1: Conditions on early Earth made the origin of life possible  Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages 1.Abiotic synthesis of small organic molecules 2.Joining of these small molecules into macromolecules 3.Packaging of molecules into protocells, membrane- bound droplets that maintain a consistent internal chemistry 4.Origin of self-replicating molecules

7 © 2014 Pearson Education, Inc. Synthesis of Organic Compounds on Early Earth  Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, and hydrogen)  As Earth cooled, water vapor condensed into oceans, and most of the hydrogen escaped into space

8 © 2014 Pearson Education, Inc.  In the 1920s, A. I. Oparin and J. B. S. Haldane hypothesized that the early atmosphere was a reducing environment  In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible

9 © 2014 Pearson Education, Inc.  However, the evidence is not yet convincing that the early atmosphere was in fact reducing  Instead of forming in the atmosphere, the first organic compounds may have been synthesized near volcanoes or deep-sea vents  Miller-Urey-type experiments demonstrate that organic molecules could have formed with various possible atmospheres  Organic molecules have also been found in meteorites Video: Hydrothermal VentVideo: Tubeworms

10 © 2014 Pearson Education, Inc. Figure 24.3 Mass of amino acids (mg) Number of amino acids

11 © 2014 Pearson Education, Inc. Figure 24.3a

12 © 2014 Pearson Education, Inc. Abiotic Synthesis of Macromolecules  RNA monomers have been produced spontaneously from simple molecules  Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock

13 © 2014 Pearson Education, Inc. Protocells  Replication and metabolism are key properties of life and may have appeared together  Protocells may have been fluid-filled vesicles with a membrane-like structure  In water, lipids and other organic molecules can spontaneously form vesicles with a lipid bilayer

14 © 2014 Pearson Education, Inc.  Adding clay can increase the rate of vesicle formation  Vesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment

15 © 2014 Pearson Education, Inc. Figure 24.4 Vesicle boundary Precursor molecules only 1  m Relative turbidity, an index of vesicle number (a) Self-assembly Time (minutes) Precursor molecules plus montmorillonite clay 20  m (c) Absorption of RNA(b) Reproduction

16 © 2014 Pearson Education, Inc. Figure 24.4a Precursor molecules only Relative turbidity, an index of vesicle number Time (minutes) Precursor molecules plus montmorillonite clay (a) Self-assembly

17 © 2014 Pearson Education, Inc. Figure 24.4b 20  m (b) Reproduction

18 © 2014 Pearson Education, Inc. Figure 24.4c Vesicle boundary 1  m (c) Absorption of RNA

19 © 2014 Pearson Education, Inc. Self-Replicating RNA  The first genetic material was probably RNA, not DNA  RNA molecules called ribozymes have been found to catalyze many different reactions  For example, ribozymes can make complementary copies of short stretches of RNA

20 © 2014 Pearson Education, Inc.  Natural selection has produced self-replicating RNA molecules  RNA molecules that were more stable or replicated more quickly would have left the most descendant RNA molecules  The early genetic material might have formed an “RNA world”

21 © 2014 Pearson Education, Inc.  Vesicles with RNA capable of replication would have been protocells  RNA could have provided the template for DNA, a more stable genetic material

22 © 2014 Pearson Education, Inc. Fossil Evidence of Early Life  Many of the oldest fossils are stromatolites, layered rocks that formed from the activities of prokaryotes up to 3.5 billion years ago  Ancient fossils of individual prokaryotic cells have also been discovered  For example, fossilized prokaryotic cells have been found in 3.4-billion-year-old rocks from Australia

23 © 2014 Pearson Education, Inc. Figure 24.5 Time (billions of years ago) 10  m 30  m 5 cm Nonphotosynthetic bacteria Cyanobacteria Stromatolites Possible earliest appearance in fossil record

24 © 2014 Pearson Education, Inc. Figure 24.5a Time (billions of years ago) Nonphotosynthetic bacteria Cyanobacteria Stromatolites Possible earliest appearance in fossil record

25 © 2014 Pearson Education, Inc. Figure 24.5b 30  m 3-billion-year-old fossil of a cluster of nonphotosynthetic prokaryote cells

26 © 2014 Pearson Education, Inc. Figure 24.5c 5 cm 1.1-billion-year-old fossilized stromatolite

27 © 2014 Pearson Education, Inc. Figure 24.5d 10  m 1.5-billion-year-old fossil of a cyanobacterium

28 © 2014 Pearson Education, Inc.  The cyanobacteria that form stromatolites were the main photosynthetic organisms for over a billion years  Early cyanobacteria began the release of oxygen into Earth’s atmosphere  Surviving prokaryote lineages either avoided or adapted to the newly aerobic environment

29 © 2014 Pearson Education, Inc. Concept 24.2: Diverse structural and metabolic adaptations have evolved in prokaryotes  Most prokaryotes are unicellular, although some species form colonies  Most prokaryotic cells have diameters of 0.5–5 µm, much smaller than the 10–100 µm diameter of many eukaryotic cells  Prokaryotic cells have a variety of shapes  The three most common shapes are spheres (cocci), rods (bacilli), and spirals

30 © 2014 Pearson Education, Inc. Figure  m (a) Spherical (b) Rod-shaped (c) Spiral 1  m

31 © 2014 Pearson Education, Inc. Figure 24.6a (a) Spherical 1  m

32 © 2014 Pearson Education, Inc. Figure 24.6b (b) Rod-shaped 1  m

33 © 2014 Pearson Education, Inc. Figure 24.6c 3  m (c) Spiral

34 © 2014 Pearson Education, Inc. Cell-Surface Structures  A key feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment  Eukaryote cell walls are made of cellulose or chitin  Bacterial cell walls contain peptidoglycan, a network of modified sugars cross-linked by polypeptides

35 © 2014 Pearson Education, Inc.  Archaeal cell walls contain polysaccharides and proteins but lack peptidoglycan  Scientists use the Gram stain to classify bacteria by cell wall composition  Gram-positive bacteria have simpler walls with a large amount of peptidoglycan  Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic

36 © 2014 Pearson Education, Inc. Figure 24.7 Peptido- glycan layer Cell wall Gram-negative bacteria 10  m Gram-positive bacteria (b) Gram-negative bacteria (a) Gram-positive bacteria Plasma membrane Plasma membrane Peptidoglycan layer Cell wall Outer membrane Carbohydrate portion of lipopolysaccharide

37 © 2014 Pearson Education, Inc. Figure 24.7a Peptido- glycan layer Cell wall (a) Gram-positive bacteria Plasma membrane

38 © 2014 Pearson Education, Inc. Figure 24.7b (b) Gram-negative bacteria Plasma membrane Peptidoglycan layer Cell wall Outer membrane Carbohydrate portion of lipopolysaccharide

39 © 2014 Pearson Education, Inc. Figure 24.7c Gram-negative bacteria 10  m Gram-positive bacteria

40 © 2014 Pearson Education, Inc.  Many antibiotics target peptidoglycan and damage bacterial cell walls  Gram-negative bacteria are more likely to be antibiotic resistant  A polysaccharide or protein layer called a capsule covers many prokaryotes

41 © 2014 Pearson Education, Inc. Figure 24.8 Bacterial cell wall Bacterial capsule Tonsil cell 200 nm

42 © 2014 Pearson Education, Inc.  Some bacteria develop resistant cells called endospores when they lack an essential nutrient  Other bacteria have fimbriae, which allow them to stick to their substrate or other individuals in a colony  Pili (or sex pili) are longer than fimbriae and allow prokaryotes to exchange DNA

43 © 2014 Pearson Education, Inc. Figure 24.9 Fimbriae 1  m

44 © 2014 Pearson Education, Inc. Motility  In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from a stimulus  Chemotaxis is the movement toward or away from a chemical stimulus

45 © 2014 Pearson Education, Inc.  Most motile bacteria propel themselves by flagella scattered about the surface or concentrated at one or both ends  Flagella of bacteria, archaea, and eukaryotes are composed of different proteins and likely evolved independently

46 © 2014 Pearson Education, Inc. Figure Flagellum Filament 20 nm Hook Motor Cell wall Rod Peptidoglycan layer Plasma membrane

47 © 2014 Pearson Education, Inc. Figure 24.10a 20 nm Hook Motor

48 © 2014 Pearson Education, Inc. Evolutionary Origins of Bacterial Flagella  Bacterial flagella are composed of a motor, hook, and filament  Many of the flagella’s proteins are modified versions of proteins that perform other tasks in bacteria  Flagella likely evolved as existing proteins were added to an ancestral secretory system  This is an example of exaptation, where existing structures take on new functions through descent with modification

49 © 2014 Pearson Education, Inc. Internal Organization and DNA  Prokaryotic cells usually lack complex compartmentalization  Some prokaryotes do have specialized membranes that perform metabolic functions  These are usually infoldings of the plasma membrane

50 © 2014 Pearson Education, Inc. Figure Respiratory membrane 0.2  m 1  m Thylakoid membranes (a) Aerobic prokaryote(b) Photosynthetic prokaryote

51 © 2014 Pearson Education, Inc. Figure 24.11a Respiratory membrane 0.2  m (a) Aerobic prokaryote

52 © 2014 Pearson Education, Inc. Figure 24.11b 1  m Thylakoid membranes (b) Photosynthetic prokaryote

53 © 2014 Pearson Education, Inc.  The prokaryotic genome has less DNA than the eukaryotic genome  Most of the genome consists of a circular chromosome  The chromosome is not surrounded by a membrane; it is located in the nucleoid region  Some species of bacteria also have smaller rings of DNA called plasmids

54 © 2014 Pearson Education, Inc. Figure Plasmids 1  m Chromosome

55 © 2014 Pearson Education, Inc.  There are some differences between prokaryotes and eukaryotes in DNA replication, transcription, and translation  These allow people to use some antibiotics to inhibit bacterial growth without harming themselves

56 © 2014 Pearson Education, Inc. Nutritional and Metabolic Adaptations  Prokaryotes can be categorized by how they obtain energy and carbon  Phototrophs obtain energy from light  Chemotrophs obtain energy from chemicals  Autotrophs require CO 2 as a carbon source  Heterotrophs require an organic nutrient to make organic compounds

57 © 2014 Pearson Education, Inc.  Energy and carbon sources are combined to give four major modes of nutrition  Photoautotrophy  Chemoautotrophy  Photoheterotrophy  Chemoheterotrophy

58 © 2014 Pearson Education, Inc. Table 24.1

59 © 2014 Pearson Education, Inc. The Role of Oxygen in Metabolism  Prokaryotic metabolism varies with respect to O 2  Obligate aerobes require O 2 for cellular respiration  Obligate anaerobes are poisoned by O 2 and use fermentation or anaerobic respiration, in which substances other than O 2 act as electron acceptors  Facultative anaerobes can survive with or without O 2

60 © 2014 Pearson Education, Inc. Nitrogen Metabolism  Nitrogen is essential for the production of amino acids and nucleic acids  Prokaryotes can metabolize nitrogen in a variety of ways  In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N 2 ) to ammonia (NH 3 )

61 © 2014 Pearson Education, Inc. Metabolic Cooperation  Cooperation between prokaryotes allows them to use environmental resources they could not use as individual cells  In the cyanobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts (or heterocytes) exchange metabolic products

62 © 2014 Pearson Education, Inc. Figure  m Heterocyst Photosynthetic cells

63 © 2014 Pearson Education, Inc.  In some prokaryotic species, metabolic cooperation occurs in surface-coating colonies called biofilms

64 © 2014 Pearson Education, Inc. Reproduction  Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours  Key features of prokaryotic biology allow them to divide quickly  They are small  They reproduce by binary fission  They have short generation times

65 © 2014 Pearson Education, Inc. Adaptations of Prokaryotes: A Summary  The ongoing success of prokaryotes is an extraordinary example of physiological and metabolic diversification  Prokaryotic diversification can be viewed as a first great wave of adaptive radiation in the evolutionary history of life

66 © 2014 Pearson Education, Inc.  Prokaryotes have considerable genetic variation  Three factors contribute to this genetic diversity  Rapid reproduction  Mutation  Genetic recombination Concept 24.3: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes

67 © 2014 Pearson Education, Inc. Rapid Reproduction and Mutation  Prokaryotes reproduce by binary fission, and offspring cells are generally identical  Mutation rates during binary fission are low, but because of rapid reproduction, mutations can accumulate rapidly in a population  High diversity from mutations allows for rapid evolution  Prokaryotes are not “primitive” but are highly evolved

68 © 2014 Pearson Education, Inc. Figure Experiment 0.1 mL (population sample) Results Daily serial transfer Old tube (discarded after transfer) New tube (9.9 mL growth medium) Population growth rate (relative to ancestral population) Generation 10,00020,00015,000 5,

69 © 2014 Pearson Education, Inc. Figure 24.14a Results Population growth rate (relative to ancestral population) Generation 10,00020,00015,000 5,

70 © 2014 Pearson Education, Inc. Genetic Recombination  Genetic recombination, the combining of DNA from two sources, contributes to diversity  Prokaryotic DNA from different individuals can be brought together by transformation, transduction, and conjugation  Movement of genes among individuals from different species is called horizontal gene transfer

71 © 2014 Pearson Education, Inc. Transformation and Transduction  A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation  Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)

72 © 2014 Pearson Education, Inc. Figure Phage infects bacterial donor cell with A  and B  alleles. Donor cell A  B  Phage DNA

73 © 2014 Pearson Education, Inc. Figure Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Donor cell AA BB A  B  Phage DNA

74 © 2014 Pearson Education, Inc. Figure Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Donor cell AA AA BB A  B  Phage DNA

75 © 2014 Pearson Education, Inc Phage infects bacterial donor cell with A  and B  alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Phage with A  allele infects bacterial recipient cell. Recipient cell Crossing over Donor cell A − B − AA AA AA BB A  B  Phage DNA Figure

76 © 2014 Pearson Education, Inc. Figure Phage infects bacterial donor cell with A  and B  alleles. Incorporation of phage DNA creates recombinant cell with genotype A  B . Phage DNA is replicated and proteins synthesized. Fragment of DNA with A  allele is packaged within a phage capsid. Phage with A  allele infects bacterial recipient cell. Recombinant cell Recipient cell Crossing over Donor cell A  B − A − B − AA AA AA BB A  B  Phage DNA

77 © 2014 Pearson Education, Inc. Conjugation and Plasmids  Conjugation is the process where genetic material is transferred between prokaryotic cells  In bacteria, the DNA transfer is one way  In E. coli, the donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA

78 © 2014 Pearson Education, Inc. Figure Sex pilus 1  m

79 © 2014 Pearson Education, Inc.  The F factor is a piece of DNA required for the production of pili  Cells containing the F plasmid (F + ) function as DNA donors during conjugation  Cells without the F factor (F – ) function as DNA recipients during conjugation  The F factor is transferable during conjugation

80 © 2014 Pearson Education, Inc. Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient)

81 © 2014 Pearson Education, Inc. Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) Broken strand peels off and enters F − cell.

82 © 2014 Pearson Education, Inc. Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) Broken strand peels off and enters F − cell. Donor and recipient cells synthesize complementary DNA strands.

83 © 2014 Pearson Education, Inc. Figure One strand of F  cell plasmid DNA breaks at arrowhead. Bacterial chromosome Bacterial chromosome F plasmid Mating bridge F  cell (donor) F − cell (recipient) F  cell F  cell Broken strand peels off and enters F − cell. Recipient cell is now a recombinant F  cell. Donor and recipient cells synthesize complementary DNA strands.

84 © 2014 Pearson Education, Inc.  The F factor can also be integrated into the chromosome  A cell with the F factor built into its chromosomes functions as a donor during conjugation  The recipient becomes a recombinant bacterium, with DNA from two different cells

85 © 2014 Pearson Education, Inc. R Plasmids and Antibiotic Resistance  Genes for antibiotic resistance are carried in R plasmids  Antibiotics kill sensitive bacteria, but not bacteria with specific R plasmids  Through natural selection, the fraction of bacteria with genes for resistance increases in a population exposed to antibiotics  Antibiotic-resistant strains of bacteria are becoming more common

86 © 2014 Pearson Education, Inc. Concept 24.4: Prokaryotes have radiated into a diverse set of lineages  Prokaryotes have radiated extensively due to diverse structural and metabolic adaptations  Prokaryotes inhabit every environment known to support life

87 © 2014 Pearson Education, Inc. An Overview of Prokaryotic Diversity  Applying molecular systematics to the investigation of prokaryotic phylogeny has produced dramatic results  Molecular systematics led to the splitting of prokaryotes into bacteria and archaea  Molecular systematists continue to work on the phylogeny of prokaryotes

88 © 2014 Pearson Education, Inc. Figure UNIVERSAL ANCESTOR Domain Eukarya Gram-positive bacteria Cyanobacteria Spirochetes Chlamydias Proteobacteria Nanoarchaeotes Crenarchaeotes Euryarchaeotes Korarchaeotes Eukaryotes Domain Archaea Domain Bacteria

89 © 2014 Pearson Education, Inc.  The use of polymerase chain reaction (PCR) has allowed for more rapid sequencing of prokaryote genomes  A handful of soil may contain 10,000 prokaryotic species  Horizontal gene transfer between prokaryotes obscures the root of the tree of life

90 © 2014 Pearson Education, Inc. Bacteria  Bacteria include the vast majority of prokaryotes familiar to most people  Diverse nutritional types are scattered among the major groups of bacteria Video: Tubeworms

91 © 2014 Pearson Education, Inc. Figure 24.UN01 Eukarya Bacteria Archaea

92 © 2014 Pearson Education, Inc. Figure 24.19a Alpha subgroup Beta subgroup Gamma subgroup Delta subgroup Epsilon subgroup Rhizobium (arrows) (TEM) Nitrosomonas (TEM) Thiomargarita namibiensis (LM) Helicobacter pylori (TEM) Chondromyces crocatus (SEM) Proteo- bacteria Alpha Beta Gamma Delta Epsilon 2.5  m 1  m 2  m 300  m 200  m

93 © 2014 Pearson Education, Inc.  Proteobacteria are gram-negative bacteria including photoautotrophs, chemoautotrophs, and heterotrophs  Some are anaerobic and others aerobic

94 © 2014 Pearson Education, Inc. Figure 24.19aa Proteobacteria Alpha Beta Gamma Delta Epsilon

95 © 2014 Pearson Education, Inc.  Members of the subgroup alpha proteobacteria are closely associated with eukaryotic hosts in many cases  Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis  Example: Rhizobium, which forms root nodules in legumes and fixes atmospheric N 2  Example: Agrobacterium, which produces tumors in plants and is used in genetic engineering

96 © 2014 Pearson Education, Inc. Figure 24.19ab Alpha subgroup Rhizobium (arrows) inside a root cell of a legume (TEM) 2.5  m

97 © 2014 Pearson Education, Inc.  Members of the subgroup beta proteobacteria are nutritionally diverse  Example: the soil bacterium Nitrosomonas, which converts NH 4 + to NO 2 –

98 © 2014 Pearson Education, Inc. Figure 24.19ac Beta subgroup Nitrosomonas (colorized TEM) 1  m

99 © 2014 Pearson Education, Inc.  The subgroup gamma proteobacteria includes sulfur bacteria such as Thiomargarita namibiensis and pathogens such as Legionella, Salmonella, and Vibrio cholerae  Escherichia coli resides in the intestines of many mammals and is not normally pathogenic

100 © 2014 Pearson Education, Inc. Figure 24.19ad Gamma subgroup Thiomargarita namibiensis containing sulfur wastes (LM) 200  m

101 © 2014 Pearson Education, Inc.  The subgroup delta proteobacteria includes the slime-secreting myxobacteria and bdellovibrios, a bacteria that attacks other bacteria

102 © 2014 Pearson Education, Inc. Figure 24.19ae Delta subgroup Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) 300  m

103 © 2014 Pearson Education, Inc.  The subgroup epsilon proteobacteria contains many pathogens including Campylobacter, which causes blood poisoning, and Helicobacter pylori, which causes stomach ulcers

104 © 2014 Pearson Education, Inc. Figure 24.19af Epsilon subgroup Helicobacter pylori (colorized TEM) 2  m

105 © 2014 Pearson Education, Inc. Figure 24.19b Spirochetes Cyanobacteria Gram-positive bacteria Chlamydias Leptospira (TEM) Oscillatoria Streptomyces (SEM) Chlamydia (arrows) (TEM) Mycoplasmas (SEM) 2.5  m 40  m 5  m 2  m 5  m

106 © 2014 Pearson Education, Inc.  Chlamydias are parasites that live within animal cells  Chlamydia trachomatis causes blindness and nongonococcal urethritis by sexual transmission

107 © 2014 Pearson Education, Inc. Figure 24.19ba Chlamydias Chlamydia (arrows) inside an animal cell (colorized TEM) 2.5  m

108 © 2014 Pearson Education, Inc.  Spirochetes are helical heterotrophs  Some are parasites, including Treponema pallidum, which causes syphilis, and Borrelia burgdorferi, which causes Lyme disease

109 © 2014 Pearson Education, Inc. Figure 24.19bb Spirochetes Leptospira, a spirochete (colorized TEM) 5  m

110 © 2014 Pearson Education, Inc.  Cyanobacteria are photoautotrophs that generate O 2  Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

111 © 2014 Pearson Education, Inc. Figure 24.19bc Cyanobacteria Oscillatoria, a filamentous cyanobacterium 40  m

112 © 2014 Pearson Education, Inc.  Gram-positive bacteria include  Actinomycetes, which decompose soil  Streptomyces, which are a source of antibiotics  Bacillus anthracis, the cause of anthrax  Clostridium botulinum, the cause of botulism  Some Staphylococcus and Streptococcus, which can be pathogenic  Mycoplasms, the smallest known cells

113 © 2014 Pearson Education, Inc. Figure 24.19bd Gram-positive bacteria Streptomyces, the source of many antibiotics (SEM) 5  m

114 © 2014 Pearson Education, Inc. Figure 24.19be Gram-positive bacteria Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM) 2  m

115 © 2014 Pearson Education, Inc. Archaea  Archaea share certain traits with bacteria and other traits with eukaryotes

116 © 2014 Pearson Education, Inc. Figure 24.UN02 Eukarya Bacteria Archaea

117 © 2014 Pearson Education, Inc. Table 24.2

118 © 2014 Pearson Education, Inc. Table 24.2a

119 © 2014 Pearson Education, Inc. Table 24.2b

120 © 2014 Pearson Education, Inc.  Some archaea live in extreme environments and are called extremophiles  Extreme halophiles live in highly saline environments  Extreme thermophiles thrive in very hot environments Video: Cyanobacteria (Oscillatoria)

121 © 2014 Pearson Education, Inc. Figure 24.20

122 © 2014 Pearson Education, Inc.  Methanogens produce methane as a waste product  Methanogens are strict anaerobes and are poisoned by O 2  Methanogens live in swamps and marshes, in the guts of cattle, and near deep-sea hydrothermal vents

123 © 2014 Pearson Education, Inc. Figure  m

124 © 2014 Pearson Education, Inc. Figure 24.21a

125 © 2014 Pearson Education, Inc. Figure 24.21b 2  m

126 © 2014 Pearson Education, Inc.  Recent metagenomic studies have revealed many new groups of archaea  Some of these may offer clues to the early evolution of life on Earth

127 © 2014 Pearson Education, Inc. Concept 24.5: Prokaryotes play crucial roles in the biosphere  Prokaryotes are so important that if they were to disappear, the prospects for any other life surviving would be dim

128 © 2014 Pearson Education, Inc. Chemical Recycling  Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems  Chemoheterotrophic prokaryotes function as decomposers, breaking down dead organisms and waste products

129 © 2014 Pearson Education, Inc.  Prokaryotes can sometimes increase the availability of nitrogen, phosphorus, and potassium for plant growth  Prokaryotes can also “immobilize” or decrease the availability of nutrients

130 © 2014 Pearson Education, Inc. Figure Seedlings growing in the lab Soil treatment Uptake of K by plants (mg) Strain 1Strain 2 Strain 3No bacteria

131 © 2014 Pearson Education, Inc. Figure 24.22a Seedlings growing in the lab

132 © 2014 Pearson Education, Inc. Ecological Interactions  Symbiosis is an ecological relationship in which two species live in close contact: a larger host and smaller symbiont  Prokaryotes often form symbiotic relationships with larger organisms

133 © 2014 Pearson Education, Inc.  In mutualism, both symbiotic organisms benefit  In commensalism, one organism benefits while neither harming nor helping the other in any significant way  In parasitism, an organism called a parasite harms but does not kill its host  Parasites that cause disease are called pathogens

134 © 2014 Pearson Education, Inc. Figure 24.23

135 © 2014 Pearson Education, Inc.  The ecological communities of hydrothermal vents depend on chemoautotrophic bacteria for energy

136 © 2014 Pearson Education, Inc. Impact on Humans  The best-known prokaryotes are pathogens, but many others have positive interactions with humans

137 © 2014 Pearson Education, Inc. Mutualistic Bacteria  Human intestines are home to about 500–1,000 species of bacteria  Many of these are mutualists and break down food that is undigested by our intestines

138 © 2014 Pearson Education, Inc. Pathogenic Bacteria  Prokaryotes cause about half of all human diseases  For example, Lyme disease is caused by a bacterium and carried by ticks

139 © 2014 Pearson Education, Inc. Figure  m

140 © 2014 Pearson Education, Inc. Figure 24.24a

141 © 2014 Pearson Education, Inc. Figure 24.24b

142 © 2014 Pearson Education, Inc. Figure 24.24c 5  m

143 © 2014 Pearson Education, Inc.  Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins  Exotoxins are secreted and cause disease even if the prokaryotes that produce them are not present  Endotoxins are released only when bacteria die and their cell walls break down

144 © 2014 Pearson Education, Inc.  Horizontal gene transfer can spread genes associated with virulence  For example, pathogenic strains of the normally harmless E. coli bacteria have emerged through horizontal gene transfer

145 © 2014 Pearson Education, Inc. Prokaryotes in Research and Technology  Experiments using prokaryotes have led to important advances in DNA technology  For example, E. coli is used in gene cloning  For example, Agrobacterium tumefaciens is used to produce transgenic plants

146 © 2014 Pearson Education, Inc.  Bacteria can now be used to make natural plastics  Prokaryotes are the principal agents in bioremediation, the use of organisms to remove pollutants from the environment  Bacteria can be engineered to produce vitamins, antibiotics, and hormones  Bacteria are also being engineered to produce ethanol from waste biomass

147 © 2014 Pearson Education, Inc. Figure (a) (b)

148 © 2014 Pearson Education, Inc. Figure 24.25a (a)

149 © 2014 Pearson Education, Inc. Figure 24.25b (b)

150 © 2014 Pearson Education, Inc. Figure 24.26

151 © 2014 Pearson Education, Inc. Figure 24.UN03

152 © 2014 Pearson Education, Inc. Figure 24.UN04 Fimbriae Cell wall Capsule Flagella Sex pilus Internal organization Circular chromosome

153 © 2014 Pearson Education, Inc. Figure 24.UN05


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