Transcript Ch. 27 & 28 Notes

Chapter 27 & 28
Prokaryotes & Protists
Ch. 27 ~ Prokaryotes
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Overview: They’re (Almost) Everywhere!
Most prokaryotes are microscopic
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But what they lack in size they more than make up for in
numbers
The number of prokaryotes in a single handful of fertile soil
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Is greater than the number of people who have ever lived
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Prokaryotes thrive almost everywhere
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Including places too acidic, too salty, too cold, or too hot for
most other organisms
Figure 27.1
27.1 ~ Structural, functional, and genetic
adaptations contribute to prokaryotic success
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Most prokaryotes are unicellular
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Although some species form colonies
Prokaryotic cells have a variety of shapes
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The three most common of which are spheres (cocci), rods
(bacilli), and spirals
1 m
(a) Spherical (cocci)
2 m
(b) Rod-shaped (bacilli)
5 m
(c) Spiral
Cell-Surface Structures
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One of the most important features of nearly all
prokaryotic cells
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Is their cell wall, which maintains cell shape, provides
physical protection, and prevents the cell from bursting
in a hypotonic environment
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Using a technique called the Gram stain
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Scientists can classify many bacterial species into two
groups based on cell wall composition, Gram-positive and
Gram-negative
Lipopolysaccharide
Cell wall
Peptidoglycan
layer
Cell wall
Outer
membrane
Peptidoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Grampositive
bacteria
Gramnegative
bacteria
20 m
(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.
Figure 27.3a, b
(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.
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The cell wall of many prokaryotes
 Is covered by a capsule, a sticky layer of
polysaccharide or protein
200 nm
Capsule
Figure 27.4
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Some prokaryotes have fimbriae and pili
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Which allow them to stick to their substrate or other individuals
in a colony
Fimbriae
200 nm
Figure 27.5
Motility
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Most motile bacteria propel themselves by flagella
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Which are structurally and functionally different from eukaryotic
flagella
Flagellum
Filament
50 nm
Cell wall
Hook
Basal apparatus
Figure 27.6
Plasma
membrane
Internal and Genomic Organization
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Prokaryotic cells
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Usually lack complex compartmentalization
Some prokaryotes
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Do have specialized membranes that perform metabolic functions
0.2 m
1 m
Respiratory
membrane
Thylakoid
membranes
Figure 27.7a, b
(a) Aerobic prokaryote
(b) Photosynthetic prokaryote
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The typical prokaryotic genome
 Is a ring of DNA that is not surrounded by a membrane
and that is located in a nucleoid region
Chromosome
Figure 27.8
1 m
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Some species of bacteria
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Also have smaller rings of DNA called plasmids
Draw a prokaryotic cell and label the DNA and plasmids
Prokaryotes reproduce quickly by binary fission
And can divide every 1–3 hours
Many prokaryotes form endospores
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Which can remain viable in harsh conditions for centuries
Endos
pore
Figure
27.9
0.3
m
27.2
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A great diversity of nutritional and metabolic adaptations
have evolved in prokaryotes
Examples of all four models of nutrition are found among
prokaryotes:
List Energy source & Carbon source:
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Photoautotrophy
Chemoautotrophy
Photoheterotrophy
Chemoheterotrophy
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Major nutritional modes in prokaryotes
Table 27.1
27.3
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Molecular systematics is illuminating prokaryotic phylogeny
Until the late 20th century
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Systematists based prokaryotic taxonomy on phenotypic
criteria
Applying molecular systematics to the investigation of
prokaryotic phylogeny
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Has produced dramatic results
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A tentative phylogeny of some of the major taxa of
prokaryotes based on molecular systematics
Domain
Archaea
Domain Bacteria
Proteobacteria
Figure 27.12
Universal ancestor
Domain
Eukarya
Bacteria
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Diverse nutritional types
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Are scattered among the major groups of bacteria
The two largest groups are
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The proteobacteria and the Gram-positive bacteria
2.5 m
Chlamydias, spirochetes, Gram-positive bacteria, and
cyanobacteria
5 m
Chlamydia (arrows) inside an
animal cell (colorized TEM)
1 m
5 m
Leptospira, a spirochete
(colorized TEM)
Hundreds of mycoplasmas
Streptomyces, the source of
covering a human fibroblast cell
many antibiotics (colorized SEM) (colorized SEM)
50 m
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Figure 27.13
Two species of Oscillatoria,
filamentous cyanobacteria (LM)
Archaea
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Archaea share certain
traits with bacteria
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And other traits
with eukaryotes
Table 27.2
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Some archaea live in extreme environments
Extreme thermophiles thrive in very hot environments
Extreme halophiles live in high saline environments
Colorful “salt-loving”
archae live in these
ponds near San
Fransisco. Used for
commercial salt
production.
Methanogens
Live in swamps and
marshes and
produce methane as
a waste product
27.4
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Prokaryotes play crucial roles in the biosphere
Chemical Recycling
Prokaryotes play a major role in the continual recycling of
chemical elements between the living and nonliving
components of the environment in ecosystems
Chemoheterotrophic prokaryotes function as decomposers
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Breaking down corpses, dead vegetation, and waste products
Nitrogen-fixing prokaryotes
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Add usable nitrogen to the environment
Symbiotic Relationships
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Many prokaryotes 
Live with other organisms in symbiotic relationships such as
mutualism and commensalism
Figure 27.15
27.5
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Prokaryotes have both harmful and beneficial impacts on
humans
Some prokaryotes are human pathogens
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But many others have positive interactions with humans
Prokaryotes cause about half of all human diseases
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Lyme disease is an example
Figure
27.16
5
µm
Prokaryotes in Research and Technology
 Experiments using prokaryotes have led to important advances in
DNA technology
 Prokaryotes are the principal agents in bioremediation
 The use of organisms to remove pollutants from the environment
 Prokaryotes are also major tools in
 Mining, the synthesis of vitamins, production of antibiotics,
hormones, and other products
Ch. 28 ~ Protists
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28.1: Protists are an extremely diverse assortment of
eukaryotes
Protists are more diverse than all other eukaryotes
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And are no longer classified in a single kingdom
Most protists are unicellular, colonial or
multicellular
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Protists, the most nutritionally diverse of all
eukaryotes, include
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Photoautotrophs, which contain chloroplasts
Heterotrophs, which absorb organic molecules or ingest
larger food particles
Mixotrophs, which combine photosynthesis and heterotrophic
nutrition
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There is now considerable evidence that much of protist
diversity has its origins in endosymbiosis
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Cladogram of Protists:
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28.3: Euglenozoans have flagella with a unique internal
structure
Euglenozoa is a diverse clade that includes
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Predatory heterotrophs, photosynthetic autotrophs, and pathogenic
parasites
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Dinoflagellates
Are a diverse group of aquatic
photoautotrophs and heterotrophs
 Are abundant components of both
marine and freshwater phytoplankton
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Ciliates, a large varied group of protists
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Are named for their use of cilia to move and feed
Have large macronuclei and small micronuclei
Conjugation – Two cells exchange haploid
micronuclei (similar to prokaryotic conjugation).
 **Produces genetic variation
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28.5 Hairy and smooth flagella
1. Diatom – Surrounded by a two part
glass like wall and are a major
component of phytoplankton.
Phytoplankton
account for half of
the photosynthetic
activity on earth –
responsible for
much of the oxygen
in our atmosphere.
2. Golden Algae – Have two flagella and
their color results from carotenoids.
3. Brown Algae – multicellular mostly
marine protists, commercially used;
seaweeds
28.6 Threadlike pseudopodia
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Pseudopodia extend and help to injest microorganisms.
28.7 ~ Amoebozoans
Lobed shaped pseudopodia
*Entamoebas – parasites of
vertebrates and cause amebic
dysentry in humans.
*Slime molds – extend their
pseudopodia through
decomposing material,
engulfing food by
phagocytosis.
28.8 ~ Red & Green Algae are the
closest relatives of land plants.