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Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Bacteria and Archaea:
The Prokaryotic Domains
TER 26
Nitrogen cycle
Mycobacterium tuberculosis
Color-enhanced images shows
rod-shaped bacterium
responsible for tuberculosis (Raven
et al 2002)
Endosymbiotic Theory
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Structure of a Eukaryotic Animal Cell
Structure of a Prokaryotic Cell
Prokaryotic cells have a simple interior
organization compared to Eukaryotes.
-True nucleus lacking
-Cytoskeleton lacking-support from rigid cell wall
-Membrane-bound organelles lacking (in most)
Structure of a Eukaryotic Plant Cell
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
structure and function
origins, evolution and diversity
ecological function and relationships
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
1. Prokaryote Phylogeny
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Genome of the Archaeon
Methanococcus jannaschii was
sequenced in 1996. Sequencing of M.
jannashcii confirmed Carl Woese’s longstanding hypothesis that life traces back to
three main lineages, one of which
(Archaea) includes prokaryotes that share
a more recent common ancestry with
eukaryotes than with the prokaryotic “true
bacteria”
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Prokaryotic Structure and Function
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
(Keaton 1993)
Cyanobacteria 10 um dia.
E. coli 1X2 um
Mycoplasma 0.3-0.8 um dia.
Bacteriophage 0.07X 0.2 um
Viroid 0.01 X 0.3 um
Lymphocycte 10 um dia.
Largest known prokaryote is
the marine bacterium
Thiomargarita namibiensis;
bright white cell in upper left,
about .75 mm dia., attached to
two dead ones. Fruitfly in
picture for size comparison.
Paramecium 30X 75 um
Sizes of viruses, bacteria and eukaryotes
compared Most bacteria are 1-5 um diameter
(most Eukaryotic cells are 10-100 um)
Bacillus on the head of a pin
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Raven et al 2002
Spherical coccus
(Enterococcus)
Pseudomonas
aeruginosa
Streptococcus
Spirillum
volutans
Bacterial Form
Rod-shaped bacillus
(E. coli)
Three shapes are especially common among bacteria –
spheres, rods and spirals
Most are unicellular, some aggregate transiently, some
form permanent aggregations of identical cells;some
show division of labor between two or more specialized
cell times
Helical spirilla
(|Aquaspirillum spirosa)
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Scanning electron micrograph of a colony of streptomyces, one of the
actinomycetes. The actinomycetes have a much more complicated
morphology than most other bacteria. (Keaton and Gould 1993)
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
•Most bacterial cell walls
contain peptidoglycan (lacking
in Archaea)
•Gram staining is an important
technique for identifying
bacterial; cells stain
differentially based on
structure and composition of
walls
•Pathogenesis is related to
cell wall structure and
composition
•Many antibiotics act by
preventing formation of cell
walls, by inhibiting synthesis
of cross-links in peptidoglycan
•Many prokaryotes produce
capsules that function in
adherance and protection
Penicillium
chrysogenum
Neisseria
gonorrhoeae
•Many prokaryotes have
surface appendages called pili
that are function in adherance
E. coli
The exterior surfaces of Prokaryotes. Almost all prokaryotes have a cell wall, and in
most that wall contains peptidoglycan – polymers of modified sugars that are crosslinked by short polypeptides
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Aquaspirillum sinosum
Mechanisms of Motility Many bacteria
are motile. Fllagellar action is the most
common,but not the only mechanism,
for generating movement.
Spirillum volutans
Borrelia burgdorferi
•Prokaryotic flagella
•Flagella-like helical filaments
•Growing gelatinous threads
Motility Behavior
Lyme disease
symptoms, and the
disease vector – a
tick
•Kinesis
•Taxis
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
0.05 um
1 um
Electron micrograph of E. coli
shoing long helical flagella.
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Vibrio cholerae (pathogen responsbible for cholera); the
unsheathed core visible at top of photo is composed of a single
crystal of the protein flagellin.
In intact flagella, core is surrounded by a flexible
sheath. Rotary motion of the motor creates a kind
of rotary motion when organism swims.
Bacteria swim by rotating their flagella.
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
mesosome
•various specialized
membranes, but lacking
extensive
compartmentalization by
internal membranes
plasma
membrane
DNA
The mesosome is an infolding
of the plasma membrane
serves as a point of
attachment for DNA in some
bacterial cells
Infoldings of plasma
membrane, similar in
ways to cristae of
mitochondria, function
in cellular respiration
in aerobic bacteria
•ribosomes present but
differ from eukaryotic ones
in size and composition
Exensive folded photosynthetic
membranes are visisble in Prochloron
cell. The single, circular DNA
molecule is located in the clear area
in the central region of the cell.
•genomes are smaller and
simpler than in eukaryotes;
one major chromosome
and, in some species,
plasmids
•Processes of DNA
replicatin and protein
translation are generally
similar to eukaryotes
Thylakoid
membranes of
photosynthetic
cyanobacteria
Cellular and Genomic Organization The organization of cellular components, including
the genome, differs substantially between prokaryotes and eukaryotes
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Cell division
Asexual reproduction
by cell division via
binary fission
Mechanisms of gene
transfer
-transformation
-conjugation
-transduction
Adaptation
short generation time
allows favorable
mutations and novel
genomes arising from
gene transfer to
spread quickly in
rapidly reprducing
Growth virtual
geometric growth while
in environments with
unlimited resources
Prokaryote Reproduction and Population Growth Prokaryote populations grow and adapt rapidly,
through asexual reproduction as well as mechanisms involving gene transfer
Chapter 26: Bacteria and Archaea: the Prokaryotic Domains
Dormancy and
Endosporulation Some
bacteria form highly
resistant spores under
harsh environmental
conditions
Sporulating Bacillus cell
Antibiotic synthesis
Some prokaryotes (and
protists and fungi)
synthesize and release
antibiotic chemicals that
inhibit growth of other
microbes
Bacillus anthracus
Adaptations to Harsh Environmental Conditions: Some bacteria are capable of
dormancy, endosporulation and antibiotic synthesis