Transcript Ch 16

Introduction: How Ancient Bacteria Changed the
World
 Virtually all metabolic pathways on Earth evolved
in prokaryotic cells, before the evolution of
eukaryotes
 The products generated by prokaryotic metabolism
changed the Earth’s atmosphere and rocks
 Fossilized stromatolites from 3 billion years ago
contain the fossils of photosynthetic cyanobacteria
– These bacteria produced O2 and made Earth’s
atmosphere aerobic
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Introduction: How Ancient Bacteria Changed the
World
 Living stromatolites still form in the warm, shallow
waters of Shark Bay, western Australia
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PROKARYOTES
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16.1 Prokaryotes are diverse and widespread
 Prokaryotes lived alone on Earth for over 1 billion
years
– They remain the most numerous and widespread
organisms on Earth
– The total biomass of prokaryotes is ten times that of
eukaryotes
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16.1 Prokaryotes are diverse and widespread
 Most prokaryotes are 1–5 µm in diameter (vs. 10–
100 µm for eukaryotic cells)
 More prokaryotes live in your mouth than the total
number of humans that have ever lived
 There are ten times as many prokaryotes living in
and on your body as the number of cells in your
body
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16.1 Prokaryotes are diverse and widespread
 Prokaryotes live in cold, hot, salty, acidic, and
alkaline habitats
 Although some bacteria are pathogenic and
cause disease, most bacteria on our bodies are
benign or beneficial
– Several hundred species of bacteria live in and on our
bodies, decomposing dead skin cells, supplying
essential vitamins, and guarding against pathogenic
organisms
 Prokaryotes in soil decompose dead organisms,
sustaining chemical cycles
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16.2 Bacteria and archaea are the two main
branches of prokaryotic evolution
 The two prokaryotic domains, Bacteria and
Archaea, diverged soon after life on Earth arose
 Present day Archaea and Eukarya evolved from a
common ancestor, complicated by gene transfer
between prokaryotic lineages
 Some genes of Archaea are similar to bacterial
genes, some are similar to eukaryotic genes, and
some are unique to Archaea
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16.4 Various structural features contribute to the
success of prokaryotes
 Prokaryotic cell walls maintain cell shape, provide
physical protection, and prevent the cell from
bursting in a hypotonic environment
– In a hypertonic environment, most prokaryotes lose
water and shrink away from their wall
 The cell walls of Archaea and Bacteria differ
Video: Prokaryotic Flagella (Salmonella typhimurium)
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16.4 Various structural features contribute to the
success of prokaryotes
 Bacterial cell walls can be distinguished with a
gram stain
– Gram-positive bacteria have simple walls with a thick
layer of peptidoglycan
– Gram-negative bacteria have complex walls with less
peptidoglycan and an outer membrane of lipids
bonded to carbohydrates
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Capsule
16.4 Various structural features contribute to the
success of prokaryotes
 Some prokaryotes stick to the substrate or each
other with hair-like appendages called pili
 Sex pili join prokaryotes during conjugation
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Pili
16.4 Various structural features contribute to the
success of prokaryotes
 The flagella of Bacteria and Archaea allow them
to move in response to chemical and physical
signals in their environment
 The prokaryotic flagellum is a naked protein
without microtubules
– The flagellum rotates like a propeller
 Are prokaryotic flagella homologous or
analogous to eukaryotic flagella?
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Flagellum
Plasma
membrane
Cell wall
Rotary movement of
each flagellum
16.4 Various structural features contribute to the
success of prokaryotes
 Some prokaryotes can withstand harsh conditions
by forming endospores within an outer cell
– The endospore has a thick protective coat
– It can dehydrate and is tolerant of extreme heat or
cold
 When conditions improve, the endospore absorbs
water and resumes growth, sometimes after
centuries
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Endospore
16.4 Various structural features contribute to the
success of prokaryotes
 Some prokaryotic cells have specialized
membranes that perform metabolic functions
– Aerobic prokaryotes carry out cellular respiration on
infoldings of the plasma membrane
– Where is cellular respiration carried out in a eukaryote?
– Cyanobacteria carry out photosynthesis on infolded
thylakoid membranes
– Where is photosynthesis carried out in a photosynthetic
eukaryote?
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Respiratory
membrane
Thylakoid
membrane
16.4 Various structural features contribute to the
success of prokaryotes
 Prokaryotic DNA forms a circular chromosome
– Smaller rings of DNA called plasmids carry genes
that may provide resistance to antibiotics or
metabolize rare nutrients, among other metabolic
activities
 Many prokaryotes can transfer genes, such as
antibiotic resistance genes, within or between
species
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Energy source
CO2
Light
Chemical
Photoautotrophs
Chemoautotrophs
Carbon
source
Organic
Photoheterotrophs Chemoheterotrophs
compounds
16.5 Prokaryotes obtain nourishment in a variety
of ways
 In some prokaryotes, metabolic cooperation occurs
in surface-coating colonies called biofilms
– Biofilms form when cells in a colony secrete signaling
molecules that recruit nearby cells
– Channels in the biofilm allow nutrients and wastes to
move inside and outside the biofilm
 Biofilms cause ear and urinary tract infections and
the dental plaque that produces tooth decay
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16.6 Archaea thrive in extreme environments—
and in other habitats
 Archaea are among the most abundant cells on
Earth
 They are a major life-form in the oceans
Video: Tubeworms
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16.7 Bacteria include a diverse assemblage of
prokaryotes
 Clades of gram-negative bacteria
– Alpha proteobacteria
– Rhizobium species live in legume nodules and fix
atmospheric N2
– Photosynthetic gamma proteobacteria
– Sulfur bacteria oxidize H2S
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16.7 Bacteria include a diverse assemblage of
prokaryotes
 Clades of gram-negative bacteria
– Delta proteobacteria
– Myxobacteria form elaborate colonies and congregate
into fruiting bodies that release resistant spores
– Chlamydias live inside eukaryotic host cells
– Chlamydias cause blindness and sexually transmitted
disease
– Spirochetes are helical bacteria
– Spirochetes cause syphilis and Lyme disease
Video: Cyanobacteria (Oscillatoria)
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Nitrogen-fixing
cells
Photosynthetic
cells
16.7 Bacteria include a diverse assemblage of
prokaryotes
 Clades of gram-positive bacteria
– Actinomycetes are common soil bacteria that
decompose organic matter
– Streptomyces is a source of many antibiotics
– Mycoplasmas lack cell walls
– They are the tiniest of all known cells, with diameters as
small as 0.1 µm (about 5 times the size of a ribosome)
– Cyanobacteria carry out oxygen-generating
photosynthesis
– Ancient cyanobacteria formed stromatolites that made
the atmosphere aerobic
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16.8 CONNECTION: Some bacteria cause disease
 Pathogenic bacteria cause disease by producing
poisonous exotoxins or endotoxins
– Exotoxins are proteins secreted by bacterial cells
– Some of the most powerful toxins known are
exotoxins, including the toxin that causes lockjaw
– Staphylococcus aureus produces several exotoxins,
including one that causes deadly toxic shock
syndrome
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16.8 CONNECTION: Some bacteria cause disease
 Endotoxins are components of the outer
membrane of gram-negative bacteria, released
when the cell dies or is digested by a defensive cell
– Endotoxins produce septic shock, bacterial meningitis,
and food poisoning
– The most widespread pest-carried disease in the
United States is Lyme disease, caused by the
spirochaete Borrelia burgdorferi
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Spirochete
that causes
Lyme disease
“Bull’s-eye” rash
Tick that
carries
the Lyme
disease
bacterium
Spirochete
that causes
Lyme disease
Tick that
carries
the Lyme
disease
bacterium
“Bull’s-eye” rash
16.9 CONNECTION: Bacteria can be used as
biological weapons
 The bacterium that causes anthrax can be used as
biological weapons
– Bacillus anthracis forms hardy endospores
– Weaponizing anthrax involves manufacturing
endospores that disperse easily in air, where they are
inhaled and germinate in the lungs
 The Biological Weapons Convention has been
signed by 103 nations, who have pledged never to
develop or store biological weapons
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16.10 CONNECTION: Prokaryotes help recycle
chemicals and clean up the environment
 Prokaryotes are key participants in chemical
cycles, making nitrogen available to plants and
thus animals
 They also decompose organic wastes and dead
organisms to inorganic chemicals
 Bioremediation is the use of organisms to
remove pollutants from soil, air, or water
– Prokaryotes are decomposers in sewage treatment
and can clean up oil spills and toxic mine wastes
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Rotating
spray arm
Rock bed
coated with
aerobic
bacteria
and fungi
Liquid wastes
Outflow
Rotating
spray arm
Rock bed
coated with
aerobic
bacteria
and fungi
Liquid wastes
Outflow
PROTISTS
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16.11 Protists are an extremely diverse assortment
of eukaryotes
 Protists constitute several kingdoms within the
domain Eukarya
 Protists obtain their nutrition in a variety of ways
– Algae are autotrophic protists
– Protozoans are heterotrophic protists, eating bacteria
and other protists
– Fungus-like protists obtain organic molecules by
absorption
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16.11 Protists are an extremely diverse assortment
of eukaryotes
 Symbiosis is a close association between
organisms of two or more species
– Endosymbiosis—living within another
– Termite endosymbionts digest cellulose in the wood
eaten by the host
– The protists have endosymbiotic prokaryotes that
metabolize the cellulose
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16.11 Protists are an extremely diverse assortment
of eukaryotes
 Protists are eukaryotes, with
– Membrane-bound chromosomes
– Multiple chromosomes
– Flagella or cilia with 9 + 2 pattern of microtubules
 Some protists have a very high level of cellular
complexity
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16.12 EVOLUTION CONNECTION: Secondary
endosymbiosis is the key to protist diversity
 What is the origin of the enormous diversity of
protists?
– Complex eukaryotic cells evolved when prokaryotes
took up residence within larger prokaryotes
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Cyanobacterium
Primary
endosymbiosis
Nucleus
Heterotrophic
eukaryote
Evolved into
chloroplast
Green alga
Nucleus
Chloroplast
Cyanobacterium
Primary
endosymbiosis
Autotrophic
eukaryotes
Nucleus
Heterotrophic
eukaryote
Evolved into
chloroplast
Nucleus
Chloroplast
Red alga
Green alga
Nucleus
Chloroplast
Cyanobacterium
Primary
endosymbiosis
Autotrophic
eukaryotes
Nucleus
Heterotrophic
eukaryote
Evolved into
chloroplast
Nucleus
Chloroplast
Red alga
Heterotrophic
eukaryotes
Green alga
Nucleus
Chloroplast
Secondary
endosymbiosis
Cyanobacterium
Primary
endosymbiosis
Autotrophic
eukaryotes
Heterotrophic
eukaryotes
Nucleus
Heterotrophic
eukaryote
Evolved into
chloroplast
Secondary
endosymbiosis
Nucleus
Chloroplast
Red alga
Green alga
Nucleus
Chloroplast
Secondary
endosymbiosis
Remnant of
green alga
Euglenozoans
Cyanobacterium
Primary
endosymbiosis
Autotrophic
eukaryotes
Heterotrophic
eukaryotes
Remnant of
red alga
Nucleus
Heterotrophic
eukaryote
Dinoflagellates
Evolved into
chloroplast
Secondary
endosymbiosis
Apicomplexans
Nucleus
Chloroplast
Red alga
Stramenopiles
16.13 A tentative phylogeny of eukaryotes includes
multiple clades of protists
 The taxonomy of protists remains a work in
progress
– The names, boundaries, and placement of clades will
continue to change as genomes of more protists are
sequenced and compared
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Diplomonads
Parabasalids
Euglenozoans
Alveolates
Dinoflagellates
Apicomplexans
Ciliates
Stramenopiles
Diatoms
Brown algae
Water molds
Forams
Radiolarians
Red algae
Green
algae
Chlorophytes
Charophytes
Amoebozoans
Land plants
Amoebas
Slime molds
Fungi
Choanoflagellates
Animals
16.14 Diplomonads and parabasalids have
modified mitochondria
 Diplomonads may be the most ancient surviving
lineage of eukaryotes
– They have modified mitochondria without DNA or
electron transport chains
– Most are anaerobic
 Parabasalids are heterotrophic protists with
modified mitochondria that generate some energy
anaerobically
– The parasite Trichomonas vaginalis is sexually
transmitted, feeding on white blood cells and bacteria
living in the cells lining the vagina
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Flagella
Undulating
membrane
16.15 Euglenozoans have flagella with a unique
internal structure
 Euglenozoans are a diverse clade of protists
– Their common feature is a crystalline rod of unknown
function inside their flagella
 Euglenozoans include heterotrophs, photosynthetic
autotrophs, and pathogenic parasites
Video: Euglena
Video: Euglena Motion
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16.16 Alveolates have sacs beneath the plasma
membrane
 Alveolates have membrane-enclosed sacs or
alveoli beneath the plasma membrane
 Dinoflagellates are important members of
marine and freshwater phytoplankton
– Some live within coral animals, feeding coral reef
communities
– Dinoflagellate blooms cause red tides
 Ciliates use cilia to move and feed.
 Apicomplexans are animal parasites such as
Plasmodium, which causes malaria
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16.16 Alveolates have sacs beneath the plasma
membrane
Video: Dinoflagellate
Video: Paramecium Cilia
Video: Paramecium Vacuole
Video: Vorticella Cilia
Video: Vorticella Detail
Video: Vorticella Habitat
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Cilia
Macronucleus
16.17 Stramenopiles have “hairy” and smooth
flagella
 Stramenopiles are named for their “hairy”
flagellum, usually paired with a “smooth” flagellum
– Water molds are fungus-like and decompose dead
organisms in freshwater habitats
– Diatoms are unicellular, with silicate cell walls
– Brown algae are large, complex algae called
seaweeds; all are multicellular and most are marine
Video: Water Mold Oogonium
Video: Diatoms Moving
Video: Water Mold Zoospores
Video: Various Diatoms
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16.18 Amoebozoans have lobe-shaped
pseudopodia
 Amoebas move and feed by means of
pseudopodia
 Members of the clade amoebozoans include
many free-living amoebas, some parasitic
amoebas, and slime molds
– All have lobe-shaped pseudopodia
Video: Amoeba
Video: Plasmodial Slime Mold Streaming
Video: Amoeba Pseudopodia
Video: Plasmodial Slime Mold Zoom
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16.18 Amoebozoans have lobe-shaped
pseudopodia
 A plasmodial slime mold is an amoebozoan that
forms a plasmodium, a multinucleate mass of
cytoplasm
– The plasmodium extends pseudopodia through soil and
rotting logs, engulfing food by phagocytosis as it grows
– Under adverse conditions, the plasmodium forms
reproductive structures that produce spores
 Cellular slime molds live as solitary amoeboid
cells
– When food is scarce, the amoeboid cells swarm
together, forming a slug-like aggregate that migrates,
before forming a fruiting body borne on a stalk
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16.19 Foraminiferans and radiolarians have
threadlike pseudopodia
 Foraminiferans and radiolarians move and feed by
means of threadlike pseudopodia
 Foraminiferans live in marine and freshwater
– They have porous tests composed of calcium
carbonate, with small pores through which
pseudopodia extend
 Radiolarians produce an internal silicate skeleton
– The test is composed of organic materials
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16.20 Red algae and green algae are the closest
relatives of land plants
 Red algae are typically soft-bodied, but some
have cell walls encrusted with hard, chalky
deposits
 Green algae split into two groups, the
chlorophytes and the charophytes
– The charophytes are the closest living relatives of
land plants
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16.20 Red algae and green algae are the closest
relatives of land plants
Video: Volvox Falgella
Video: Volvox Colony
Video: Volvox Daughter
Video: Volvox Female Spheroid
Video: Chlamydomonas
Video: Volvox Inversion 1
Video: Volvox Inversion 2
Video: Volvox Sperm and Female
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Chlamydomonas
Volvox
colonies
16.20 Red algae and green algae are the closest
relatives of land plants
 The life cycles of most green algae involve the
alternation of generations, in which a haploid
(n) gametophyte alternates with a diploid (2n)
sporophyte generation
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Mitosis
Male
gametophyte
Spores
Mitosis
Meiosis
Gametes
Female
gametophyte
Fusion of
gametes
Sporophyte
Zygote
Mitosis
Key
Haploid (n)
Diploid (2n)
16.21 EVOLUTION CONNECTION:
Multicellularity evolved several times in
eukaryotes
 Multicellularity evolved in several different lineages,
probably by specialization of the cells of colonial
protists.
– Stramenopile lineage brown algae
– Unnamed lineage red algae, green algae, land plants
– Opisthokont lineage fungi and animals
 Multicellular life arose over a billion years ago.
 By 543 million years ago, diverse animals and
multicellular algae lived in aquatic environments;
plants and fungi colonized land 500 million years ago
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1
Unicellular
protist
Colony
Locomotor
cells
2
1
Foodsynthesizing
cells
Unicellular
protist
Colony
Early multicellular organism
with specialized, interdependent cells
Gamete
Locomotor
cells
2
1
3
Somatic
cells
Foodsynthesizing
cells
Unicellular
protist
Colony
Early multicellular organism
with specialized, interdependent cells
Later organism that
produces gametes
Nutritional Mode
Energy Source
Photoautotroph
Sunlight
Chemoautotroph
Inorganic chemicals
Photoheterotroph
Sunlight
Chemoheterotroph
Organic compounds
Carbon Source
CO2
Organic compounds
(a)
(b)
(c)
(d)
You should now be able to
1. Compare the characteristics of the three domains
of life; explain why biologists consider Archaea to
be more closely related to Eukarya than to
Bacteria
2. Describe the structures and functions of the
diverse features of prokaryotes; explain how these
features have contributed to their success
3. Describe the nutritional diversity of prokaryotes;
explain the significance of biofilms
4. Describe the diverse types of Archaea living in
extreme and moderate environments
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You should now be able to
5. Distinguish between the subgroups of the domain
Bacteria, noting the particular structure, special
features, and habitats of each group
6. Distinguish between bacterial exotoxins and
endotoxins, noting examples of each
7. Describe the positive natural roles of prokaryotes
8. Describe the basic types of protists; explain why
biologists currently think that they represent
many clades
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You should now be able to
9. Explain how primary endosymbiosis and
secondary endosymbiosis led to further cellular
diversity
10. Describe the major protist clades noting
characteristics and examples of each
11. Describe the life cycle of Ulva, noting each form
in the alternation of generations and how each is
produced
12. Explain how multicellular life may have evolved in
eukaryotes
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