Download Archaea

Overview
of
lecture:
•An
introduc7on
to
Eukaryo7c
microorganisms
•General
characteris7cs
of
Eukaryo7c
cell
structure
and
func7on
Introduction to Microbiology
•Highlight
how
eukaryo7c
cells
differ
from
prokaryo7c
cells
Eukaryotic microorganisms:
Cell structure and function
•Eukaryo7c
cells
are
more
complex
than
prokaryo7c
cells
Dr
A.
Fleming
Eukaryotic cell morphology is diverse
You
are
here
•
3
domains
•Arose
from
a
common
ancestor
•Archaea
and
Eucaryota
evolved
independently,
separate
from
bacteria
Algae;
Volvox
Protozoa;
Paramecium
Fungi;
Yeast
Fungi;
Aspergillus
Eukaryotic microorganisms exhibit
extreme diversity
Diatoms
Eukaryotic microorganisms can exist
as multicellular macroscopic structures
•Have
a
silicon‐based
cell
wall
Mushroom
Amoeba
•Have
no
cell
wall
Eukaryo7c
cells
are
complex
•Have
membrane
bound
nuclei
•Have
numerous
organelles
•Have
more
complex
reproduc7on
processes
‐
mitosis
and
meiosis
Cell
organelles
•Defini7on:
intracellular
structures
that
perform
specific
func7ons
•Analagous
to
the
func7on
of
organs
in
the
body
•Organelles
do
not
have
to
be
membrane
bound
The
cytoplasmic
matrix
is
an
organelle
•Supports
all
other
organelles
and
biochemical
processes
A
major
component
of
the
cytoplasmic
matrix
is
the
cytoskeleton
•Highly
dynamic
•Changes
in
the
cytoplasmic
matrix
are
essen7al
for
cell
func7on
•A
network
of
3
types
of
filaments
•plays
roles
in
cell
shape
and
movement
Cytoskeleton
filaments:
1.
Microfilaments
2.
Microtubules
•Ac7n
protein
filaments
•4
–
7
nm
in
diameter
•Can
be
scaRered
or
organised
into
networks
•Role
:
•Involved
in
cell
mo7on
and
cell
shape
change
•a
helix
of
α‐tubulin
and
β‐tubulin
subunits
•Thin
cylinders
~
25
nm
in
diameter
•Role:
1.Maintain
cell
shape
2.Cooperate
with
microfilaments
for
cell
movement
3.Par7cipate
in
intracellular
transport
Pathogens
can
hijack
the
eukaryo7c
cytoskeleton
3.
Intermediate
filaments
•Assembled
from
a
mixed
group
of
different
proteins
•10
nm
in
diameter
Role:
•Not
well
characterised
•Can
have
a
role
in
cell‐cell
adhesion
The
nucleus
•Listeria
monocytogenes
releases
a
ActA
virulence
factor
•Ac7n
polymerisa7on
can
propel
Listeria
monocytogenes
through
a
host
cell
Eukaryo7c
Genomes
are
large
Organism
Nucleus
Prokaryote
Eukaryote
•Contains
DNA
•Bound
by
the
double
membrane
nuclear
envelope
Genome
size
/
bp
No.
of
genes
Phi‐X
174
5,386
10
Epstein‐Barr
Virus
172,282
80
Bacillus
sub*lis
4,214,814
4,779
E.
coli
K12
4,639,221
4,377
Saccharomyces
cerevisiae
12,495,682
6000
Drosophila
melanogaster
122,653,977
13,379
Anopheles
gambiae 278,244,063
13,683
Human
3.3
x
109
~20,500
Human
mitochondria
16,569
37
DNA
is
packaged
as
chroma7n
Gene
transcrip7on
in
eukaryotes
DNA
double
helix
nucleosome
Eukaryo7c
RNA
Polymerases
folded
nucleosomes
Histones:
H2A,
H2B
H3,
H4
Pol
II
Pol
I
Pol
III
Transcrip7on
chroma7n
loop:
Messenger
RNA
rRNA
~100,000
bp
DNA
Transla7on
50
–
70
%
of
total
transcrip7on
mito7c
chromosome
5SrRNA
and
transfer
RNA
Proteins
•Bacteria
have
one
RNA
polymerase
Gene
expression
in
prokaryotes
RNA
Polymerase
σ
‐35
‐10
Gene
expression
in
eukaryotes
RNA
Polymerase
gene1
gene2
gene3
DNA
Operon
TF
TBP
Gene
TATA
box
Polycistronic
mRNA
Monocistronic
mRNA
Export
Protein
•RNA
polymerase
is
directed
by
sigma
factors
•Transcrip7on
and
transla7on
can
occur
simultaneously
Protein
•RNA
polymerase
is
directed
by
TBP
and
transcrip7on
factors
•Genes
may
contain
introns
(non‐coding
regions)
Eukaryo7c
ribosomes
The
nucleolus
Prokaryo7c
Eukaryo7c
Nucleus
Nucleolus
Prokaryote
Eukaryote
•Very
dense
structure
•not
membrane
bound
•Site
of
ribosomal
RNA
synthesis
and
ribosome
assembly
•Immature
ribosomes
leave
the
nucleus
via
nuclear
envelope
pores
Organelles
of
the
secretory
pathway
•Eukaryo7c
ribosomes
are
bigger
protein
factories
The
endoplasmic
re7culum
(ER)
•A
network
of
membranous
tubes
and
flaRened
sacks
(cisternae)
•Con7nuous
with
nuclear
envelope
Other
organelles
have
roles
in:
•Movement
of
materials
within
the
cell
and
out
of
the
cell
Smooth
ER
Rough
ER
•Involved
in
synthesis
&
export
of
proteins
and
lipids
•Site
of
cell
membrane
synthesis
The
biosynthe7c‐secretory
pathway
The
Golgi
apparatus
•Composed
of
flaRened
membranous
sacks
(cisternae)
A
stack
=
dictyosome
Maturing
face
4‐8
cisternae
/
stack
Dis7nct
polarity
E.g.
Protein
Secre7on
•Movement
of
materials
within
or
outside
of
cell
1.Protein
synthesis
2.Glycosyla7on
in
ER
1.
3.
Fusion
with
Cis
face
of
Golgi
Forming
face
4.Packaging
in
Golgi
Role:
•Processing,
packaging
and
secre7on
of
macromolecules
Proteins
are
subject
to
quality
control
•Misfolded
proteins
are
ubiquitylated
•Modified
proteins
are
degraded
by
the
proteosome
Proteosome
5.Transport
Vesicle
release
4.
5.
2.
3.
The
proteosome
•A
huge
cylindrical
protein
complex
•Proteolysis
is
ATP‐dependent
Transport
of
materials
into
the
cell
•The
Endocy7c
pathway
•Materials
are
enclosed
within
the
plasma
membrane
•Delivery
to
a
lysosome
via
three
pathways
1.Phagocytosis
(protrusions)
Lysosomes
•Single
membrane
bound
spherical
structures
•Range
from
50nm
to
several
um
in
size
•Contain
hydroly7c
enzymes
2.Endocytosis
(invagina7ons)
3.Autophagy
(recycling
of
cytosolic
components)
•Diges7on
occurs
in
the
lysosome
•Small
products
leave
the
lysosome
for
use
as
nutrients
Mitochondria
Role:
•Intracellular
diges7on
The
proposed
origin
of
the
Eukaryo7c
cell
•The
site
of
ATP
synthesis
•The
endosymbio7c
theory
Size
=
0.5
–
10um
1
‐
1000
/
cell
Prokaryo7c
ancestor:
ANAEROBIC
1.Lost
the
cell
wall
/
phagocytosis
of
prokaryotes
for
nutrients
2.Formed
symbio7c
rela7onship
with
an
engulfed
aerobic
bacteria
3.Photosynthe7c
cyanobacteria
promoted
an
oxic
environment
4.Selected
the
above
cell
type
5.The
endosymbio7c
aerobic
bacterium
developed
into
mitochondria
•They
are
double
membrane
structures:
an
inner
membrane
and
outer
membrane
•The
inner
matrix
is
where
ATP
is
formed
Modern
eukaryote:
AEROBIC
Eukaryo7c
reproduc7on
is
more
complex
asexual
reproduc7on:
Mitosis
Sexual
reproduc7on:
Meiosis
•Chromosome
number
is
reduced
from
diploid
(2N)
to
haploid
(1N)
•Haploid
cells
may
act
as
gametes
to
reform
diploid
organisms
•A
complex
process
involving
several
stages
•Each
new
nucleus
acquires
a
duplicate
set
of
chromosomes
Diversity
of
eukaryo7c
external
cell
structures
Other
eukaryotes
have
a
rigid
cell
wall
Yeast
Diatom
(algae)
Amoeba
proteus
•Some
eukaryotes
have
no
cell
wall
Rigid
cell
wall
Glucose‐based
Silica‐based
cell
wall
(frustule)
Cilia
and
Flagella
Pro7sts
have
a
pellicle
underneath
the
membrane
Cilia
Flagella
Euglena
Paramecium
Euglena
spirogyra
•Aid
in
mo7lity
•the
pellicle
is
striated,
olen
bearing
rows
of
papillae
Eukaryotic cilia and flagellar structure
PaRerns
of
Flagellar
and
Ciliary
movement
wave
•Membrane bound organelle, ~0.2m thick
•Extensions of microtubule doublets arranged in a 9 + 2 structure
•Originate from a basal body (centriole)
beat
The
Archaea:
a
third
form
of
life
Comparison
of
Prokaryo7c
and
Eukaryo7c
cells
Prokaryote
Eukaryote
•Eukaryotes
are
more
structurally
and
func7onally
complex
•Eukaryotes
have
a
membrane
–bound
nucleus
•Eukaryotes
have
a
diverse
collec7on
of
organelles
•Replica7on
is
more
complex
–mitosis
and
meoisis
•Eukaryotes
carry
out
complex
processes
such
as
enodcytosis,
amoeboid
movement
etc.
•The
Archaea:
•Originally
described
as
bacteria
(archaebacteria)
•
are
they
are
prokaryotes
–
have
no
nucleus
??
•Now
proposed
to
form
a
dis7nct
domain
–
a
‘third
form’
of
life
Archaea
have
unique
proper7es
Archaea
and
eukaryotes
share
a
common
ancestry
•All
life
arose
from
a
common
ancestor
•Archaea
and
Eukaryotes
evolved
separately
from
the
bacteria
•Archaea
and
eukaryotes
diverged
and
became
separate
domains
•This
common
evolu7on
is
reflected
in
the
way
they
process
gene7c
informa7on
*
*
Archaea:
General
cell
structure
and
morphology
•Look
similar
to
bacteria
•Cell
membrane
is
bound
by
a
cell
wall
•Have
a
diverse
morphology
•Range
in
size
from
0.1
–
200
μm
•Commonly
unicellular
Methanococcus
Janaschii
‐cocci
with
flagella
Methanothermus
fervidus
‐Short
bacillus
• Originally
idenRfied
in
extreme
environments
Haloquadratum
Walsbyi
‐square
?
Methanosarcina
Barkeri
‐lobed
cocci
Methanobacterium
Thermoautotrophicum
‐filamentous
How
extreme
is
extreme
?
Archaea
• extremophiles
– Hyperthermophiles
– Methanogens
– Extreme
halophiles
Thermophiles
and
hyperthermophiles
Pyrolobus
fumarii
•Pyrolobus
was
found
at
a
Hydrothermal
vent
(Black
Smoker)
The
thermophile
record
holder
(so
far....)
•Archaea
Strain
121
•105
ºC
is
its
op7mal
growth
temperature.
•
It
cannot
live
below
90
ºC
Psychrophiles:
found
in
cold
regions
Strain
121
•Found
at
a
hydrothermal
vents
Halophile
habitat
and
structure
Barophiles:
•
Found
at
the
boRom
of
ocean
trenches
&
gorges,
such
as
the
Mariana
Trench
•Resistant
to
extreme
pressures
Were
the
Archaea
able
to
survive
the
violence
of
early
earth?
Did
life
on
earth
arrive
from
outer
space
?
Has
life
on
earth
spread
to
outer
space
?
•Via
comets
&
Meteorites
Could
life
originate
on
other
planets
?
Comets
&
Meteorites
•Europa
is
a
large
moon
of
Jupiter
•It
is
completely
encased
in
water
ice
•Volcanoes
could
be
ac7ve
Alien
life
?
Alien
life
?
?
Could
Archaea
be
the
future
of
life
on
earth
?
Summary
• Eukaryotes
have
a
more
complex
cell
structure
than
prokaryotes
– They
have
a
nucleus
and
numerous
organelles
yeast
• The
Archaea
form
a
third
way
of
life
• They
have
features
of
both
prokaryotes
and
eukaryotes
Extra
Reading
PrescoR,
LM
et.
Al.,
Microbiology
7th
edi7on
McGraw‐Hill,
Boston,
2008
Pages
70
‐99