Chapter 27 Prokaryotes

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Chapter 27 Prokaryotes Bacteria on the
point of a pin
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Extreme Thermophiles
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The Three Domains of Life
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Streptococcus streptochain coccusspherical
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Bacillirod-shaped
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Spirillahelical includes spirochetes
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Largest known prokaryote
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Another large prokaryote
paramecium
Prokaryotes vary in size from 0.2µ--750µ
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Within the past decade, several uncultured
bacteria were consecutively announced as the
largest known prokaryotes Epulopiscium
fishelsoni (3), Beggiatoa sp. (48), and T.
namibiensis (83). Over the years, big bacteria
have been described as "megabacteria" or
"gigantobacteria" or given names such as
"Titanospirillum" (20,30). The current holder of
the biovolume record, a chain-forming, spherical
sulfur bacterium, T. namibiensis, was discovered
only recently in the sea floor off the coast of
Namibia (83). The cells may reach 750 microm
diameter, clearly visible to the naked eye. They
form chains of cells that, due to their light
refracting sulfur globules, shine white on the
background of black mud and thus appear as a
string of pearls (Thiomargarita sulfur pearl).
Also the rod-shaped heterotrophic bacterium,
Epulopiscium fishelsoni , found in fish guts may
reach a giant size of 80 microm diameter and
600 microm length (3, 10). The largest reported
Archaea are probably the extremely thermophilic
Staphylothermus marinus, which in culture may
occasionally have cell diameters up to 15
microm (19). The smallest prokaryotes are found
among both the Archaea and the Eubacteria. The
disk-shaped cells of the archaea, Thermodiscus,
have diameters down to 0.2 microm and a
disk-thickness of 0.1-0.2 microm (87). Under
the collective designation of nanobacteria or
ultramicrobacteria, a range of cell forms with
diameters down to 0.2-0.3 microm have been
found in both natural samples and cultures (92).
Altogether, the biovolumes of prokaryotic cells
may cover a range of more than 10 orders of
magnitude, from
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Evolution of Prokaryotic Metabolism

• The Origin of Glycolysis First prokaryotes 3.5
  billion
• years ago, probably (1)anaerobic
  chemoheterotrophs. They absorbed organic
  compounds and used glycolysis
• (fermentation) to produce ATP in an atmosphere
  without
• oxygen. All forms of fermentation produced
  acidic
• compounds.
• 2. The Origin of Electron Transport Chains and
• Chemiosmosis The (2)first proton pumps were
  probably for pH regulation. (3)Later some
  bacteria used the oxidation of organic compounds
  to pump Hs to save ATP and developed the first
  Electron Transport Chains. (4)Some got so good
  at transporting Hs that they could actually
  develop a gradient and use the influx to drive
  the
• production of ATP.

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• 3. The Origin of Photosynthesis (5)The first
  light absorbing
• pigments probably provided protection by
  absorbing UV light.
• But all pigments throw off electrons when light
  shines on
• them so why wouldnt evolution find a way to
  use the energy
• of those electrons? Bacteriorhodopsin in
  extreme halophiles
• (6)uses light energy to pump Hs out of the
  cell and produce a gradient which is then used to
  produce ATP (cyclic
• photophosphorylation with Photosystem I).
• Photoheterotrophs
• 4. Cyanobacteria, Photoautotrophs, Splitting H2O
  and
• Producing O2 (7)Photosystem II evolved in
  cyanobacteria and they split water and released
  free oxygen. The oxygen was toxic to many
  organisms which became extinct. (First Great
  Extinction) Photoautotrophs

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5. Origin of Cellular Respiration (8)Some
prokaryotes modified their photosynthetic
ETCs to reduce the level of toxic O2. The
purple non-sulfur bacteria still use their
ETCs for both photosynthesis and respiration.
Eventually (9)some bacteria used O2 to
pull electrons through proton pumps and
aerobic respiration began. aerobic
chemoheterotrophs
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Cell Walls All the proteobacteria and the
eubacteria have peptidoglycan cell walls.
Archaebacteria have a different type of cell
wall. Cell walls protect bacteria from cytolysis
in hypotonic solutions but can not protect them
from plasmolysis in hypertonic solutions.
Mycoplasmas without cell walls are susceptible to
both. Penicillin denatures (noncompetitive
inhibitor) the enzyme that bacteria use to form
their cell walls and leaves them susceptible to
cytolysis.
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Gram-positive diplococcus
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Gram-positive staphlococcus and Gram-negative
diplobacillus
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Bacillus with Pilli-used for conjugation,
attachment to surfaces and snorkels for getting
oxygen
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Bacterial flagella rotate rather than bend
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Bacteria with flagella
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Bacteria with flagella
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Bacteria with flagella
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Infolding of the plasma membrane give these
bacteria respiratory membranes and
thylakoid-like membranes
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Bacteria growing on agar in a petri dish
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Mold cultures
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An anthrax endospore
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Endospores
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ARCHAEA
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Extreme halophiles in seawater evaporation ponds
that are up to 20 salt colors are from
bacteriorhodopsin a photosynthetic pigment very
similar to the pigment in our retinas
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Hot springs with extreme thermophiles
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Hydrogen Sulfide Metabolizing Chemoautotrophic
Archaea found in sulfur springs
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Eubacteria
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The Proteobacteria are a major group (phylum) of
bacteria. They include a wide variety of
pathogens, such as Escherichia,
Salmonella(rod-shaped Gram-negative
enterobacteria that causes typhoid fever and the
foodborne illness salmonellosis , Vibrio(motile
gram negative curved-rod shaped bacterium with a
polar flagellum that causes cholera in humans.) ,
Helicobacter(stomach ulcers), and many other
notable genera.1 Others are free-living, and
include many of the bacteria responsible for
nitrogen fixation. The group is defined primarily
in terms of ribosomal RNA (rRNA) sequences, and
is named for the Greek god Proteus (also the name
of a bacterial genus within the Proteobacteria),
who could change his shape, because of the great
diversity of forms found in this group.
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All Proteobacteria are Gram-negative, with an
outer membrane mainly composed of
lipopolysaccharides. Many move about using
flagella, but some are non-motile or rely on
bacterial gliding. The last include the
myxobacteria, a unique group of bacteria that can
aggregate to form multicellular fruiting bodies.
There is also a wide variety in the types of
metabolism. Most members are facultatively or
obligately anaerobic and heterotrophic, but there
are numerous exceptions. A variety of genera,
which are not closely related to each other,
convert energy from light through photosynthesis.
These are called purple bacteria, referring to
their mostly reddish pigmentation.
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Alpha Proteobacteria
Alpha Proteobacteria
Rocky Mountain Spotted Fever
Ti plasmid
Symbiosis with Legumes
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Alpha Proteobacteria
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Fruiting bodies of myxobacteria
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Helicobacter pylori causes stomach ulcers
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The Rickettsia are Gram-negative, obligate
intracellular bacteria that infect mammals and
arthropods. R. prowazekii is the agent of
epidemic typhus. During World War I,
approximately 3 million deaths resulted from
infection by this bacterium. In World War II, the
numbers were similar. This agent is carried by
the human louse therefore, disease is a
consequence of overcrowding and poor hygiene.
Rocky Mountain spotted fever and Q fever remain
relatively common.
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Rhizobium
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Streptomycetes-soil bacteria that produces an
antibiotic
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Sulfur bacteria that split H2S in photosynthesis
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Cyanobacteria with heterocysts-specialized cells
with the enzymes for nitrogen fixation
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Another Cyanobacteria
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Another Cyanobacteria
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Another Cyanobacteria
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Cyanobacteria
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Cyanobacteria
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Algae Blooms
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Spirochete
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Bull's-eye rash of a person with Lyme disease
Spirochete that causes Lyme disease
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Bull's-eye rash of a person with Lyme disease
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Deer tick that carries the spirochetes that cause
Lyme disease
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Spirochete that causes Syphilis
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Mycoplasms that cause Chlamydiae No cell wall and
smallest of eubacteria
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Mycoplasmas-covering a human fibroblast cell
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Chlamydias living inside an animal cell
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Mycoplasms that cause Chlamydiae
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Mutualism of a bioluminescent bacteria in a
headlight fish
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The yellow bacillus is a pathogenic bacteria that
causes respiratory infections on the membranes
inside the nose.
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The blue bacteria on this slide are commensal
living on the membranes inside the nose but
causing no harm.
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Opportunistic infection Kochs postulates
Gram-positive actinomycetes causes tuberculosis
destroys tissues Clostridium botulinum releases
exotoxins in food it is an obligate
anaerobe Vibrio cholerae releases an exotoxin
that causes severe diarrhea Salmonella typhi
endotoxins that cause typhoid fever, another
species of Salmonella causes common food
poisoning due to endotoxins explains why it takes
12 -48 hours for symptoms to show up
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Bioremediation bacteria breakdown sewage
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Spraying fertilizer on oil spills for
Bioremediation
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Smaller bacteria attacking a larger one
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Conjugation caught in the act