Transcript Ch 27 - Phillips Scientific Methods

Eukaryote
Classification
• Old 5 Kingdom system
Prokaryote
• Monera, Protists, Plants, Fungi,
Animals
• New 3 Domain system
– reflects a greater
understanding of evolution &
molecular evidence
• Prokaryote: Bacteria
• Prokaryote: Archaebacteria
• Eukaryotes
– Protists
– Plants
– Fungi
– Animals
Archaebacteria
&
Bacteria
Prokaryotes
Domains
Eubacteria and Archaebacteria
Prokaryotic Cell Structure
bac vid
Bacteria (Eubacteria)
-Prokaryotes
-unicellular
-most heterotrophs; some photosynthetic (cyano)
-can be aerobic or anaerobic
*obligate or facultative
Fig. 27-2
1 µm
(a) Spherical
(cocci)
2 µm
(b) Rod-shaped
(bacilli)
5 µm
(c) Spiral
Structure and Function
• 3 basic shapes: spherical (cocci), rods
(bacillus) and spiral
• Cell Wall
– Peptidoglycan covers cell, anchors
attachments
– Archaea have no (or little) peptidoglycan
Gram Staining
Gram + : simple walls, lots of Peptiodoglycan
(take on stain- purple color)
Gram - : complex walls with lipopolysaccharides
less PTG (don’t take on stain due to lipids)
– Medical significance: Gram – lipids are toxic
causing fever or shock and are resistant to
our defenses
– Gram – : antibiotic resistance (hard for drugs
to penetrate)
– Antibiotics often target peptidoglycan
Gram Stain Benefits
• Antibiotics, like penicillin break down
peptidoglycans so they are affective against
gram positive bacteria.
• Gram negative bacteria are extremely harmful
because their LPS layer is toxic. They cause
fever and even shock. Strong antibiotics and
alternative medicines are needed to kill them.
Prokaryote Cell Wall Structure
Gram-positive bacteria
peptide side
chains
cell wall
peptidoglycan
plasma membrane
protein
peptidoglycan = polysaccharides + amino acid chains
lipopolysaccharides = lipids + polysaccharides
Gram-negative bacteria
cell wall
outer membrane of
lipopolysaccharides
outer
membrane
peptidoglycan
plasma
membrane
Fig. 27-4
200 nm
Capsule
Capsule vs Fimbriae
• Sticky and covers
entire cell
• Protection from
dehydration and
shield from immune
system
• Hair like appendages
that stick
• Ex. Neisseria
gonorrhoeae sticks to
mucus membranes
• Shorter and more
numerous than sex
pilli
Fig. 27-5
Fimbriae
200 nm
Motility for most bacteria
• propel themselves by flagella that are
structurally and functionally different from
eukaryotic flagella
• PROK flagella are 1/10 the width of EUK
• PROK flagella are not covered by plasma
mem
Motility
• Different composition and propulsion
• The motor of the flagella is the basal apparatus
(rings embedded in the cell wall)
• ATP proton pump generates power by turning
hook attached
• Hook is attached to chains of flagellin
• In a heterogeneous environment, many bacteria
exhibit taxis, the ability to move toward or away
from certain stimuli
Video: Prokaryotic Flagella (Salmonella typhimurium)
Fig. 27-6
Flagellum
Filament
50 nm
Cell wall
Hook
Basal apparatus
Plasma
membrane
Fig. 27-8
Chromosome
Plasmids
1 µm
mitochondria
Variations in Cell Interior
cyanobacterium
(photosythetic) bacterium
chloroplast
aerobic bacterium
Reproduction and Adaptation
• Binary fission in optimal conditions as
often as every 20 min
• They are small and have short generation
time
• Endospores (ability to endure hardship)
Endospores
-endospores- a tough covering containing bacteria DNA.
-produced in unfavorable environments
-bacteria will lie dormant until conditions are right (years)
-extreme heat and acidic cleaners must be used to
sterilize surfaces containing endospores
-can cause- botulism in unsterilized canned foods, or
tetanus in wounds
What you need to know:
• Mechanisms that contribute to genetic diversity
in prokaryotes, including transformation,
conjugation, transduction, and mutation.
Rapid Evolution: high genetic
diversity
• 2 strains of E.coli differ in an rRNA gene
more than between a human and a
platypus
• Rapid reproduction
• Mutation
• Genetic recombination
Mutation
• Probability of a spontaneous mutation in
an E.coli gene is 1 in 10 million/division
• 2x1010 new E.coli per day
• About 2000 bacteria will have mutations
• 4300 genes total in E.coli
• 4300 x 2000 = 9 million mutation per day
in the human intestines
• Don’t memorize specific data! Just a FYI
Genetic Recombination
• Transformation: uptake foreign DNA
– Ex. Competent cells, pneumonia
• Transduction: a bacteriophage performs
horizontal gene transfer
• Conjugation- bacterial “sex”
• Plasmids often used for transformation
Fig. 27-11-4
Phage DNA
A+ B+
Transduction
A+ B+
Donor
cell
A+
Recombination
A+
A– B–
Recipient
cell
A+ B–
Recombinant cell
Conjugation and Plasmids
• Conjugation is the process where genetic
material is transferred between bacterial
cells
• Sex pili allow cells to connect and pull
together for DNA transfer
• A piece of DNA called the F factor is
required for the production of sex pili
• The F factor can exist as a separate plasmid
or as DNA within the bacterial chromosome
Fig. 27-12
Sex pilus
1 µm
The F Factor as a Plasmid
• Cells containing the F plasmid function as
DNA donors during conjugation
• Cells without the F factor function as DNA
recipients during conjugation
• The F factor is transferable during
conjugation (recipient can become donor)
Fig. 27-13
F plasmid
Bacterial chromosome
F+ cell
F+ cell
Mating
bridge
F– cell
F+ cell
Bacterial
chromosome
(a) Conjugation and transfer of an F plasmid
Hfr cell
A+
A+
A+
F factor
F– cell
A+
A–
Recombinant
F– bacterium
A–
A–
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
A+
A–
A+
R Plasmids and Antibiotic
Resistance
• R plasmids carry genes for antibiotic
resistance
• Antibiotics select for bacteria with genes that
aren’t resistant to the antibiotics
• Antibiotic resistant strains of bacteria are
becoming more common
Bacterial Diversity
-Diverse nutritional modes
-Role of oxygen in metabolism
-Nitrogen metabolism
nitrogen fixation: converting N2 from the
atmosphere into nitrates or ammonia (NH3)
Table 27-1
Fig. 27-14
Photosynthetic
cells
Heterocyte
20 µm
Heterocyte
A heterocyte (or heterocyst, in
older terminology) is a specialized
thick-walled cell that is dedicated
to fixing atmospheric nitrogen in
certain cyanobacteria. These cells
do not photosynthesize, since the
enzyme that carries out nitrogen
fixation is inhibited by oxygen.
Prokaryotic phylogeny
Eukarya
Archaea
Bacteria
Eukarya
Bacteria
Archaea
• Archaea more closely
related to eukaryotes
than bacteria
• polyphyletic
Fig. 27-16
Euryarchaeotes
Crenarchaeotes
UNIVERSAL
ANCESTOR
Nanoarchaeotes
Domain Archaea
Korarcheotes
Domain
Eukarya
Eukaryotes
Proteobacteria
Do not have to know
the specific names!
Just the trend
Spirochetes
Cyanobacteria
Gram-positive
bacteria
Domain Bacteria
Chlamydias
Table 27-2
Proteobacteria- *don’t have to know the name
• These gram-negative bacteria include
photoautotrophs, chemoautotrophs, and
heterotrophs
• Some are anaerobic, and others aerobic
-*Facultative anaerobes vs obligate
anaerobes. What’s the difference?
Fig. 27-18a
Subgroup: Alpha Proteobacteria
Alpha
Beta
Gamma
Proteobacteria
2.5 µm
Delta
Epsilon
Rhizobium (arrows) inside a
root cell of a legume (TEM)
Subgroup: Beta Proteobacteria
0.5 µm
1 µm
Subgroup: Gamma Proteobacteria
Thiomargarita namibiensis
containing sulfur wastes (LM)
Nitrosomonas (colorized TEM)
Subgroup: Delta Proteobacteria
Subgroup: Epsilon Proteobacteria
Fruiting bodies of
Chondromyces crocatus, a
myxobacterium (SEM)
Bdellovibrio bacteriophorus
attacking a larger bacterium
(colorized TEM)
2 µm
5 µm
10 µm
B. bacteriophorus
Helicobacter pylori (colorized TEM)
Subgroup: Alpha Proteobacteria
(*don’t have to know name)
• Many species are closely associated with
eukaryotic hosts
• Scientists hypothesize that mitochondria
evolved from aerobic alpha proteobacteria
through endosymbiosis
• Example: Rhizobium, which forms root
nodules in legumes and fixes atmospheric
N2
• Arrows in the next slide are Rhizobium
• Example: Agrobacterium, which produces
tumors in plants and is used in genetic
engineering
2.5 µm
Fig. 27-18c
Rhizobium (arrows) inside a root
cell of a legume (TEM)
Cyanobacteria
• These are
photoautotrophs that
generate O2
• Plant chloroplasts
likely evolved from
cyanobacteria by the
process of
endosymbiosis
Two species of Oscillatoria,
filamentous cyanobacteria (LM)
Concept 27.6: Prokaryotes have
both harmful and beneficial
impacts on humans
• Some prokaryotes are human pathogens,
but others have positive interactions with
humans
• Bacteria are important recyclers; N2 fixation, etc
• Prokaryotes cause about half of all human
diseases
• Lyme disease is an example
Fig. 27-21
5 µm
• Pathogenic prokaryotes typically cause disease by
releasing exotoxins or endotoxins
• Exotoxins cause disease once the toxin is
released, even if the prokaryotes that produce
them are no longer present. Ex- Botulism, cholera
• Endotoxins (gram – and in outer membrane)
are released only when bacteria die and their cell
walls break down. Ex- Salmonella. *Gram – have
lipopolysaccharide
• Many pathogenic bacteria are potential weapons
of bioterrorism
Archaea
• Archaea share certain traits with bacteria and
other traits with eukaryotes
• DNA and amino acid sequencing have shown that
Archaea are more related (i.e, more recent
common ancestor) to D. Eukarya than to D.
Eubacteria (see table 27.2, shown earlier in this
presentation)
Characteristics of Bacteria
DOMAIN
Bacteria
CHARACTERISTICS
-Nuclear envelope absent
-Membrane enclosed organelles
absent
-Peptidoglycan in cell walls
-Unbranched hydrocarbons in
membrane lipids
-1 kind of RNA polymerase
-Formylmethionine for initiator of
amino acids in protein synthesis
-Introns rare
-Antibiotics inhibit growth
-Circular chromosome
EXAMPLE
Alpha
Beta
Gamma
Delta
Epsilon
Chlamydias
Spirochetes
Cyanobacteria
Gram-positive
bacteria
(*don’t have to
know these!)
Characteristics Of Archaea
Archaea
•Nuclear envelope absent
•Membrane enclosed
organelles absent
•Some branched
hydrocarbons in
membrane lipids
•Several kinds of RNA
polymerase
•Methionine initiator
amino acid for protein
synthesis
•Introns present in some
genes
•Antibiotics do not inhibit
growth
•Have histones & circular
chromosome
Korarchaeotes
Euryarchaeotes
Crenarchaeotes
Nanoarchaeotes
*Don’t have to know
these!
Characteristics of Eukarya
Eukarya
-Nuclear envelope
present
-Membrane bound
organelles
-Unbranched
hydrocarbons in
membrane lipids
-Several kinds of RNA
polymerase
-Methionine initiator
amino acid for protein
synthesis
-Antibiotics do not
inhibit growth
-Histones present
Eukaryotes (plants,
animals, protists, fungi)
Most archaea live in extreme environments
• Extreme thermophiles thrive in very hot
environments
• Extreme halophiles live in high saline
environments
• Some use CO2 (not O2) to oxidize H2 and
produce methane as waste- Methanogens. Exswamps (“bubbles” are methane- CH4)
(*Aerobic organisms use O2 for oxidation. Remember
Cellular Respiration!)
Ecological Importance of Prokaryotes
• Decomposers – Convert inorganic compounds into
forms that can be taken up by other organisms
• Nitrogen fixation –
– Prokaryotes can metabolize nitrogen in a variety of
ways; In nitrogen fixation, some prokaryotes
convert atmospheric nitrogen to ammonia
• Oxygen production (if autotrophic)
• Symbiotic relationship with eukaryotes (*ex- your
digestion: remember Lac and Trp operons in
prokaryotes)
• Prokaryotes are so important to the biosphere that
if they were to disappear, the prospects for any
other life surviving would be bleak….