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Anthrax
Cutaneous
anthrax
Bacillus anthracis
Microbial Diversity
Chapt. 27 – Prokaryotes and the Origins
of Metabolic Diversity
&
Chapt. 28 – The Origins of Eukaryotic
Diversity
What are microbes?
Single-celled organisms and some
non-cellular parasites
Kinds of microbes
Non-cellular, parasitic molecules
Viruses
Viroids
Prions
Prokaryotes
Domain Bacteria
Domain Archaea
Eukaryotes
Several Kingdoms in Domain Eukarya
Nonliving parasitic molecules
Viruses
Single or double stranded RNA or DNA
with a protein coat
Common cold, Ebola, HIV
HIV
Nonliving parasitic molecules
Viruses
Single or double stranded RNA or DNA
with a protein coat
Common cold, Ebola, HIV
Viroids
Short, single strand of RNA w/o protein coat
Primarily infect plants
Prions
Protein particles w/o genetic material
Kuru, mad cow, chronic wasting disease
Kinds of microbes
Non-cellular, parasitic molecules
Viruses
Viroids
Prions
Prokaryotes
Domain Bacteria
Domain Archaea
Eukaryotes
Several Kingdoms in Domain Eukarya
Carl Woese’s 3 Domains of Life
See Fig. 27.12
Based primarily on
genetic sequence data;
e.g., small subunit ribosomal
RNA – present in all
organisms
Carl Woese’s 3 Domains of Life
Prokaryotes
Eukaryotes
NOTE: “Microbes” and
“Prokaryotes” are not
taxonomic categories
See Fig. 27.12
Carl Woese’s 3 Domains of Life
Prokaryotes
Eukaryotes
NOTE: Eukarya & Archaea
are more closely related
than either is to Bacteria
See Fig. 27.12
Carl Woese’s 3 Domains of Life
Prokaryotes
See Fig. 27.12
Eukaryotes
Even so, Archaea & Bacteria
share more structural &
functional properties than
either does with Eukarya
Microbes are microscopic, but very
diverse & extremely abundant
Bacteria on the tip of a pin
Relative sizes of microbes
Prokaryotes
Domains Bacteria & Archaea
Simple cells – with no nucleus or
membrane-bound organelles
Prokaryotes
Domains Bacteria & Archaea
Simple cells – with no nucleus or
membrane-bound organelles
First organisms on Earth – at least 3
billion years ago
The oldest known fossils
Cyanobacteria > 3 billion years old
Prokaryotes
Domains Bacteria & Archaea
Simple cells – with no nucleus or
membrane-bound organelles
First organisms on Earth – at least 3
billion years ago
Distributed globally – including many
extremophiles
Extreme Thermophiles
“Heat-loving” Archaea
Extreme Halophiles
“Salt-loving” Archaea
pink color due
to halophiles
Australian Salt Lake
Methanogens
Methane-generating Archaea
Occur in oxygen-free habitats
E.g., swamp mud, guts of ruminant animals
Ice Bacteria & Archaea
Cave Bacteria
Sometimes reaching acidity of pH 0.5
Prokaryotes
Domains Bacteria & Archaea
Simple cells – with no nucleus or
organelles
First organisms on Earth – at least 3
billion years ago
Distributed globally – including many
extremophiles
Nutrition – autotrophs & heterotrophs
Prokaryote Nutrition
All organisms require a source of
energy & carbon
Autotrophs
can obtain all
their C from
CO2
Prokaryote Nutrition
All organisms require a source of
energy & carbon
Heterotrophs
require at
least one
organic
nutrient, e.g.,
glucose
Prokaryote Nutrition
All organisms require a source of
energy & carbon
Phototrophs
obtain their
energy from
the sun
Prokaryote Nutrition
All organisms require a source of
energy & carbon
Chemotrophs
obtain their
energy from
chemical
compounds
Bacteria
Structure
Systematic / phylogenetic
relationships among bacteria are
based on genetic data, but structural
properties are indispensable for
identifying them
Bacteria
Structure
Cell wall – unique, peptidoglycan
Peptidoglycan - structural
polysaccharides
(sugars) cross-linked by
peptides (chains of amino
acids)
Two biochemical groups of bacteria:
peptidoglycan
outer
membrane
Two biochemical groups of bacteria:
peptidoglycan
outer
membrane
will stain
will not stain
Gram positive bacteria
Gram negative bacteria
Gram stain
Distinguishes different cell wall types
Gram positive
Staphylococcus aureus
Gram negative
Escherichia coli
3 common bacterial shapes:
Cocci- spheres
Spirilli- spirals
Bacilli- rods
Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer
E.g., slime layer allows bacteria to cling to
tooth enamel or other substrates
Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer
Pili & Flagella
Pili (singular: pilus)
Protein filaments that attach bacteria to
other cells & substrates
pili
Some prokaryotes have flagella
(singular: flagellum)
Used for locomotion
flagella
Base of a bacterial flagellum…
…the only known wheel in nature
50 nm
Fig. 27.6
What is “taxis”?
Motility allows some bacteria to
move towards or away from stimuli
Phototaxis
Chemotaxis
Magnetotaxis
Bacteria
Structure
Cell wall – unique, peptidoglycan
Capsules or slime layer
Pili & Flagella
Circular DNA molecule & plasmids
Bacteria
Reproduction
Asexual, through binary fission
Binary fission
Daughter cells are identical copies
Chromosome
(1)
(4)
Plasma membrane
(2)
(5)
(3)
(6)
Neither mitosis nor meiosis occurs in prokaryotes
Binary fission
E. coli
DNA
cell wall
Bacteria
Reproduction
Asexual, through binary fission
No true sexual reproduction, since neither
mitosis nor meiosis exist in
prokaryotes
Bacteria
Reproduction
Asexual, through binary fission
No true sexual reproduction, since neither
mitosis nor meiosis exist in
prokaryotes
Horizontal transfer of genetic material
Uptake of genetic material
Transformation
from the environment
Bacteria
Reproduction
Asexual, through binary fission
No true sexual reproduction, since neither
mitosis nor meiosis exist in
prokaryotes
Horizontal transfer of genetic material
Transformation
Transfer of genetic
Transduction
material between
prokaryotes by viruses
Bacteria
Reproduction
Asexual, through binary fission
No true sexual reproduction, since neither
mitosis nor meiosis exist in
prokaryotes
Horizontal transfer of genetic material
Transformation
Transduction
Direct transfer of genetic
Conjugation
material from one
prokaryote to another
Conjugation in E. coli
Sex pilus connects cells and
draws them together
Conjugation tube then forms
Sex pilus
Bacteria
Surviving harsh conditions
Endospore – forms inside a bacterium and
then persists through inhospitable conditions
endospore
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Louis Pasteur’s observations (1860s)
on decomposition disproved
spontaneous generation
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Louis Pasteur’s observations (1860s)
on decomposition disproved
spontaneous generation
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Louis Pasteur’s observations (1860s)
on decomposition disproved
spontaneous generation
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
Especially
common in the
cyanobacteria
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
Especially
common in the
cyanobacteria
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism
Rhizobium in the roots of a
soybean plant
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism, commensalism
Bacteria – Impacts on other
organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism, commensalism,
parasitism
Bacteria are often agents of disease by
producing toxins
E.g., Clostridium tetani, the species that
causes tetanus by producing a toxin that
interferes with nerve impulses and causes
muscles to spasm
Bacteria are often agents of disease by
producing toxins
Robert Koch (late 1800s) was the first person to
link diseases to specific species of bacteria
The “Germ Theory” revolutionized medicine in
the early 20th century
Koch’s Postulates guide the identification of
disease agents:
1. Find the same pathogen in each victim
2. Isolate the pathogen & grow it in pure culture
3. Induce the disease in a healthy individual from culture
4. Isolate the same pathogen after disease occurs
Bacteria – Impacts on other
Organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism, commensalism,
parasitism
What type of symbiont is Escherichia coli?
Normal strains provide K & B-complex vitamins
Bacteria – Impacts on other
Organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism, commensalism,
parasitism
What type of symbiont is Escherichia coli?
Some infectious strains cause disease
Bacteria – Impacts on other
Organisms, including
Human Society
Decomposition
Photosynthesis
N-fixation
Symbiosis
Mutualism, commensalism,
parasitism
Bioremediation
Oil spills, mine tailings, heavy metal dumps, etc.
Archaea
Structure
Several basic biochemical differences
distinguish them from Bacteria
E.g., No peptidoglycan in their cell walls
Archaea
Archaea
Many are extremophiles…
Archaea
Even so, archaea are not restricted to extreme habitats
Archaea account for 20-30% of marine microbial cells
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