Prokaryotic World
The Three Domains
Eukarya
Kingdoms:
Animalia
Plantae
Fungi
Protista
Archaea
“Extremophiles”
Prokaryotic:
cells have
no nucleus
Eukaryotic:
cells have
a nucleus
Bacteria
Bacteria
Cyanobacteria
Prokaryotic cells
Bacterial structure
Bacteria have no
nucleus, but do have:
a cell membrane
a cell wall
a capsule
flagellae or cillia
Bacterial Structure
Bacteria come in
three common
shapes:
Coccus (spherical)
Bacillus (rod-shaped)
Spirillus (spiralshaped)
Motility
Some bacteria are
motile and can move
by means of a
flagella.
A simple “wheel and
axle” arrangement
of proteins forms the
base of the
flagellum.
Reproduction
Bacteria reproduce
by binary fission
(simple cell division).
However, they can
also exchange
genetic information
by trading plasmids
(DNA rings) across
conjugation bridges.
Ecological roles
Bacteria play a wide range of roles in the
ecology.
Many are decay organisms, breaking down
dead material and releasing inorganic
compounds such as nitrogen compounds or
carbon dioxide.
Some are symbiotic organisms that live in
animal digestive systems.
Some are disease-causing organisms.
Ecological Roles
Nitrogen-fixing
bacteria are
associated the the
roots of certain
plants. These
bacteria convert
nitrogen gas into
compounds that
plants can absorb.
Escherischia coli
E. coli is a wellknown gut bacteria.
Like all prokaryotes,
it has no nucleus and
no membrane-bound
organelles, but is
highly adaptable.
E. coli
The “hot dog” shape
is a typical
“bacillius” form.
Normally, E. coli is a
part of our intestinal
flora. Out of place,
however, it can
cause serious
infections.
E. coli
In this photo, you can
see the bacterial DNA
coiled up in the center
of the organism.
Bacterial DNA forms
one long loop rather
than strands.
Small loops
(“plasmids”) can be
shared between
bacteria.
Cyanobacteria
These are
photsynthetic
bacteria that gather
in long strands.
Cyanobacteria were
probably the first
photosynthetic
organisms on the
planet.