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Chapter 27
Prokaryotes
Bacteria on the
point of a pin
Extreme Thermophiles
The Three Domains of Life
Streptococcus strepto=chain coccus=spherical
Bacilli=rod-shaped
Spirilla=helical includes spirochetes
Largest
known
prokaryote
Another large prokaryote
paramecium
Prokaryotes vary in size
from 0.2µ--750µ
Evolution of Prokaryotic Metabolism
1. The Origin of Glycolysis– First prokaryotes 3.5 billion
years ago, probably anaerobic chemoheterotrophs. They
absorbed organic compounds and used glycolysis
(fermentation) to produce ATP in an atmosphere without
oxygen
2. The Origin of Electron Transport Chains and
Chemiosmosis– The first proton pumps were probably for
pH regulation. Later some bacteria used the oxidation of
organic compounds to pump H+’s to save ATP and
developed the first Electron Transport Chains. Some
got so good at transporting H+’s that they could actually
develop a gradient and use the influx to drive the
production of ATP.
3. The Origin of Photosynthesis– The first light absorbing
pigments probably provided protection by absorbing UV light.
Bacteriorhodopsin in extreme halophiles uses light energy to
pump H+’s out of the cell and produce a gradient which is then
used to produce ATP (Photosystem I) . Photoheterotrophs
4. Cyanobacteria, Photoautotrophs, Splitting H2O and Producing
O2– 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)
5. Origin of Cellular Respiration– Some prokaryotes modified their
photosynthetic ETC’s to reduce the level of toxic O2. The
purple non-sulfur bacteria still use their ETC’s for both
photosynthesis and respiration. Eventually some bacteria used
O2 to pull electrons through proton pumps and aerobic
respiration began. aerobic chemoheterotrophs
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.
Gram-positive diplococcus
Gram-positive staphlococcus and Gram-negative diplobacillus
Bacillus with Pilli-used for conjugation, attachment to
surfaces and snorkels for getting oxygen
Bacterial flagella rotate rather than bend
Bacteria with flagella
Bacteria with flagella
Bacteria with flagella
Infolding of the plasma membrane give these bacteria
respiratory membranes and thylakoid-like membranes
Bacteria growing on agar in a petri dish
Mold cultures
An anthrax endospore
Endospores
ARCHAEA
BACTERIA
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
Hot springs with extreme thermophiles
Hydrogen Sulfide Metabolizing Chemoautotrophic Archaea
found in sulfur springs
Eubacteria
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 curvedrod 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.
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.
Alpha Proteobacteria
Alpha
Proteobacteria
Rocky Mountain Spotted Fever
Ti plasmid
Symbiosis with Legumes
Alpha Proteobacteria
Fruiting bodies of myxobacteria
Helicobacter pylori causes
stomach ulcers
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.
Rhizobium
Streptomycetes-soil bacteria that produces an antibiotic
Sulfur bacteria that split H2S in photosynthesis
Cyanobacteria with heterocysts-specialized cells
with the enzymes for nitrogen fixation
Another Cyanobacteria
Another Cyanobacteria
Another Cyanobacteria
Cyanobacteria
Algae Blooms
Spirochete that causes Lyme
disease
Bull's-eye rash of a person
with Lyme disease
Bull's-eye rash of a
person with Lyme disease
Deer tick that carries the spirochetes that cause Lyme disease
Spirochete that causes Syphilis
Spirochete
Mycoplasms that cause Chlamydiae
No cell wall and smallest of eubacteria
Mycoplasmas-covering a human fibroblast cell
Chlamydias living
inside an animal
cell
Mycoplasms that
cause Chlamydiae
Mutualism of a bioluminescent bacteria
in a “headlight fish”
The yellow bacillus is a pathogenic bacteria that causes
respiratory infections on the membranes inside the nose.
The blue bacteria on this slide are commensal living on
the membranes inside the nose but causing no harm.
Opportunistic infection
Koch’s 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
Bioremediation
bacteria breakdown
sewage
Spraying fertilizer on oil spills for Bioremediation
Smaller bacteria attacking
a larger one
Cyanobacteria
Conjugation
“caught in the
act”