Transcript cell wall - Moore Public Schools

Chapter 27
Prokaryotes
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: They’re (Almost) Everywhere!
• Most prokaryotes are microscopic, but
what they lack in size they make up for in
numbers
• There are more in a handful of fertile soil
than the number of people who ever lived
• Prokaryotes thrive almost everywhere,
including places too acidic, too salty, too
cold, or too hot for most other organisms
• They have an astonishing genetic
diversity
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WORD ROOTS
• -GEN:
EXO-:
• -OID:
HALO-:
• AN-:
MUTU--:
• ANTI-:
-PHILOS:
• BI-:
HALO-:
• CHEMO-:
PHOTO-:
• ENDO-:
SYM-:
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Concept 27.1: Structural, functional, and genetic
adaptations contribute to prokaryotic success
• Most prokaryotes are unicellular,
although some species form colonies.
• Prokaryotic cells have a variety of shapes.
• The three most common shapes
1.Spheres (cocci)
2. Rods (bacilli)
3. Spirals (spirilla)
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LE 27-2
1 µm
Spherical
(cocci)
2 µm
Rod-shaped
(bacilli)
5 µm
Spiral
Cell-Surface Structures
• An important feature of nearly all
prokaryotic cells is their cell wall,
which maintains cell shape, provides
physical protection, and prevents the
cell from bursting in a hypotonic
environment
• Using the Gram stain, scientists
classify many bacterial species into
groups based on cell wall composition,
Gram-positive and Gram-negative
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GRAM POSITIVE AND GRAM NEGATIVE
• GRAM POSITIVE: These bacteria have
simpler walls with a relatively large
amount peptidoglycan.
• GRAM NEGATIVE: These bacteria have
less peptidoglycan and are structurally
more complex, with an outer membrane
that contains lipopolysaccharides, which
are carbohydrates bonded to lipids.
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Book Page 535 Draw and label
in Notes each Gram Bacteria:
Lipopolysaccharide
Cell
wall
Pepridoglycan
layer
Cell
wall
Outer
membrane
Pepridoglycan
layer
Plasma membrane
Plasma membrane
Protein
Protein
Grampositive
bacteria
Gramnegative
bacteria
20 µm
Gram-positive
Gram-negative
• The cell wall of many
prokaryotes is covered
by a capsule, a sticky
layer of polysaccharide
or protein called a
capsule.
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LE 27-4
200 nm
Capsule
•Some prokaryotes
have fimbriae and pili,
which allow them to
stick to their
substrate or other
individuals in a colony
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LE 27-5
Fimbriae
200 nm
Motility
• Most motile bacteria propel
themselves by flagella that are
structurally and functionally
different from eukaryotic
flagella
• In a heterogeneous environment,
many bacteria exhibit taxis, the
ability to move toward or away
from certain stimuli
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LE 27-6
Flagellum
Filament
50 nm
Cell wall
Hook
Basal apparatus
Plasma
membrane
Internal and Genomic Organization
• Prokaryotic cells usually
lack complex
compartmentalization.
• Some prokaryotes do have
specialized membranes that
perform metabolic
functions
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LE 27-7
1 µm
0.2 µm
Respiratory
membrane
Thylakoid
membranes
Aerobic prokaryote
Photosynthetic prokaryote
• The typical prokaryotic
genome is a ring of DNA
that is not surrounded
by a membrane and that
is located in a nucleoid
region
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LE 27-8
Chromosome
1 µm
•Some species of
bacteria also have
smaller rings of
DNA called plasmids
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Reproduction and Adaptation
• Prokaryotes reproduce quickly
by binary fission and can
divide every 1–3 hours
• Many prokaryotes form
endospores, which can remain
viable in harsh conditions for
centuries
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LE 27-9
Endospore
0.3 µm
•Rapid reproduction
and horizontal gene
transfer facilitate
the evolution of
prokaryotes in
changing environments
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CLASS START
PROPERTY
CELL SHAPE
CELL SIZE
CELL SURFACE
MOTILITY
INTERNAL MEMBRANES
GENOMES
REPRODUCTION AND
GROWTH
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DESCRIPTION
PROPERTY
DESCRIPTION
CELL SHAPE
ROD (BACILLUS), ROUND OR SPHERE
(COCCI), SPIRAL (SPIRILLA)
CELL SIZE
CELL SURFACE
1-5 MICROMETERS IN DIAMETER
CELL WALL MADE OF PEPTIDOGLYCAN;
GRAM NEG BACTERIA ALSO HAVE OUTER
LIPOPOLYSACHARIDE MEMBRANE;
ARCHAEA LACK PEPTIDOGLYCAN; STICKY
CAPSULE FOR ADHERENCE; FIMBRAE
AND PILI FOR ATTATCHMENT OR
CONJUGATION
MOTILITY
FLAGELLA; MAY SHOW TAXIS TO
STIMULI
INTERNAL MEMBRANES
INFOLDINGS OF PLASMA MEMBRANE
MAY BE USED IN METABOLIC
FUNCTIONS
GENOMES
CIRCULAR DNA WITH LITTLE
ASSOCIATED PROTEINS IN NUCLEOID
REGION; MAY HAVE PLASMIDS WITH
ANTIBIOTIC RESISTANCE AND OTHER
GENES
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Concept 27.2: A great diversity of nutritional and
metabolic adaptations have evolved in prokaryotes
• All four models of nutrition are found among
prokaryotes:
1.Photoautotrophy
2.Chemoautotrophy
3.Photoheterotrophy
4.Chemoheterotrophy
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MODE OF
NUTRITION
ENERGY
SOURCE
CARBON
SOURCE
TYPES OF
ORGANISMS
PHOTO
AUTOTROPH
LIGHT
CO2
PHOTOSYNTHE CYANOBACTERIA,
TIC
ALGAE
PROKARYOT;
PLANTS;
CERTAIN
PROTISTS
CHEMOAUTO
TROPH
INORGANIC CO2
CHEMICALS
PHOTOHETER
OTROPH
LIGHT
CHEMOHETER
OTROPH
ORGANIC
COMPOUND
CERTAIN
PROKARYOTE
ORGANIC CERTAIN
CMPND
PROKARYOTE
ORGANIC MANY
CMPND
PROKARYOTE
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AND
EXAMPLES
SULFOLOBUS
RHODOBACTERIA,
CHLOROFLEXUS
CLOSTRIDUM
Metabolic Relationships to Oxygen
• Prokaryotic metabolism varies with
respect to oxygen:
– Obligate aerobes require oxygen
– Facultative anaerobes can survive
with or without oxygen
– Obligate anaerobes are poisoned
by oxygen
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Nitrogen Metabolism
• Prokaryotes can metabolize
nitrogen in a variety of
ways
• In nitrogen fixation, some
prokaryotes convert
atmospheric nitrogen to
ammonia
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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 exchange
metabolic products
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LE 27-10
Photosynthetic
cells
Heterocyte
20 µm
•In some prokaryotic
species, metabolic
cooperation occurs in
surface-coating
colonies called
biofilms
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 27.3: Molecular systematics is
illuminating prokaryotic phylogeny
• Until the late 20th century,
systematists based prokaryotic
taxonomy on phenotypic criteria
• Applying molecular systematics
to the investigation of
prokaryotic phylogeny has
produced dramatic results
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Lessons from Molecular Systematics
• Molecular systematics is
leading to a phylogenetic
classification of
prokaryotes
• It allows systematists to
identify major new clades
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•A tentative phylogeny
of some of the major
taxa of prokaryotes
based on molecular
systematics
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Proteobacteria
Universal ancestor
Domain
Archaea
Eukaryotes
Nanoarchaeotes
Crenarcaeotes
Domain Bacteria
Euryarchaeotes
Korarchaeotes
Gram-positive
bacteria
Cyanobacteria
Spirochetes
Chlamydias
Epsilon
Delta
Gamma
Beta
Alpha
LE 27-12
Domain
Eukarya
Bacteria
• Diverse nutritional types
are scattered among the
major groups of bacteria
• The two largest groups are
the proteobacteria and the
Gram-positive bacteria
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LE 27-13
PROTEOBACTERIA
CHLAMYDIAS
2.5 µm
2.5 µm
Subgroup: Alpha Proteobacteria
Chlamydia (arrows)
Rhizobium (arrows)
SPIROCHETES
1 µm
5 µm
Subgroup: Beta Proteobacteria
Leptospira
Nitrosomonas
GRAM-POSITIVE BACTERIA
Mycoplasmas covering
a human fibroblast cell
Streptomyces
Chromatium
5 µm
10 µm
Bdellovibrio
bacteriophorus
Chrondromyces
crocatus
2 µm
Subgroup: Epsilon Proteobacteria
Heliocobacter pylori
50 µm
CYANOBACTERIA
Subgroup: Delta Proteobacteria
Oscillatoria
1 µm
0.5 µm
5 µm
Subgroup: Gamma Proteobacteria
Archaea
•Archaea share
certain traits with
bacteria and other
traits with
eukaryotes
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YOU
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• Some archaea live in extreme
environments
• Extreme thermophiles thrive
in very hot environments
• Extreme halophiles live in high
saline environments
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•Methanogens live in
swamps and
marshes and
produce methane as
a waste product
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Concept 27.4: Prokaryotes play crucial roles in
the biosphere
• Prokaryotes are so
important to the
biosphere that if they
were to disappear, the
prospects for any other
life surviving would be
dim
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Chemical Recycling
• Prokaryotes play a major role in the
continual recycling of chemical elements
between the living and nonliving
components of ecosystems
• Chemoheterotrophic prokaryotes
function as decomposers, breaking down
corpses, dead vegetation, and waste
products
• Nitrogen-fixing prokaryotes add usable
nitrogen to the environment
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Symbiotic Relationships
• Many prokaryotes live with other
organisms in symbiotic relationships
• In mutualism, both symbiotic organisms
benefit
• In commensalism, one organism benefits
while neither harming nor helping the
other in any significant way
• In parasitism, one organism, called a
parasite, benefits at the expense of the
host
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 27.5: Prokaryotes have both
harmful and beneficial impacts on humans
•Some prokaryotes are
human pathogens, but
others have positive
interactions with
humans
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Pathogenic Prokaryotes
•Prokaryotes cause
about half of all
human diseases
•Lyme disease is an
example
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Pathogenic prokaryotes typically cause
disease by releasing exotoxins or
endotoxins
• Exotoxins 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
• Many pathogenic bacteria are potential
weapons of bioterrorism
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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
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Some other uses of prokaryotes:
– Recovery of metals from ores
– Synthesis of vitamins
– Production of antibiotics,
hormones, and other products
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