Classification
description
Transcript of Classification
Archaebacteria&
Bacteria
Classification• Old 5 Kingdom system
• 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
Prokaryote
Eukaryote
Fig. 27-2
(a) Spherical (cocci)
1 µm
(b) Rod-shaped (bacilli)
2 µm
(c) Spiral
5 µm
Structure and Function
• 3 basic shapes: spherical (cocci), rods (bacillus) and spiral
• Cell Wall– Peptidoglycan covers cell, anchors
attachments– Archaea have no peptidoglycan
Gram Staining
Gram + : simple walls, lots of PTG
Gram - : complex walls with lipopolysaccharides less PTG
– 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
peptide sidechains
cell wallpeptidoglycan
plasma membrane
protein
Gram-positive bacteria
Gram-negative bacteria
peptidoglycan
plasmamembrane
outermembrane
outer membrane of lipopolysaccharides
cell wall
peptidoglycan = polysaccharides + amino acid chainslipopolysaccharides = lipids + polysaccharides
Prokaryote Cell Wall Structure
Fig. 27-4
Capsule
200 nm
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 (Video: Prokaryotic Flagella (Salmonella typhimuriumSalmonella typhimurium))
Fig. 27-6
Flagellum
Filament
Hook
Basal apparatus
Cell wall
Plasmamembrane
50 nm
Fig. 27-8
Chromosome Plasmids
1 µm
chloroplast
mitochondria
internal membranes
for respiration
like a mitochondrion
(cristae)
internal membranes
for respiration
like a mitochondrion
(cristae)
internal membranesfor photosynthesislike a chloroplast(thylakoids)
internal membranesfor photosynthesislike a chloroplast(thylakoids)
cyanobacterium(photosythetic) bacterium aerobic bacterium
Variations in Cell Interior
Reproduction and Adaptation
• Binary fission in optimal conditions every 1-3 hours (E.coli every 20 min usually 1/24 hr)
• They are small, repro binary fission and short generation time
• Endopsores (ability to endure hardship)
Fig. 27-10EXPERIMENT
RESULTS
Daily serial transfer
0.1 mL(population sample)
Old tube(discardedaftertransfer)
New tube(9.9 mLgrowthmedium)
Fit
nes
s re
lati
veto
an
ces
tor
Generation0 5,000 10,000 15,000 20,000
1.0
1.2
1.4
1.6
1.8
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
Genetic Recombination
• Transformation: uptake foreign DNA– Ex. Competent cells, pneumonia
• Transduction: a bacteriophage performs horizontal gene transfer
• Conjugation
• Plasmids
Fig. 27-11-4
Recombinant cell
Recipientcell
A+ B–
B–
A+
A–
Recombination
A+
Donorcell
A+ B+
A+ B+
Phage DNA
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
Fig. 27-13
F plasmid
F+ cell
F– cell
Matingbridge
Bacterial chromosome
Bacterialchromosome
(a) Conjugation and transfer of an F plasmid
F+ cell
F+ cell
F– cell
(b) Conjugation and transfer of part of an Hfr bacterial chromosome
F factor
Hfr cell A+A+
A+
A+
A+A– A– A–
A– A+
RecombinantF– bacterium
R Plasmids and Antibiotic Resistance
• R plasmids carry genes for antibiotic resistance
• Antibiotics select for bacteria with genes that are resistant to the antibiotics
• Antibiotic resistant strains of bacteria are becoming more common
Bacterial Diversity
Major nutritional modesRole of oxygen in metabolismNitrogen metabolism
nitrogen fixation: converting N2 from the atmosphere into ammonia NH3
Metabolic Cooperation colony of cyanobacterium Anabaena (filaments) genes for photosynthesis (most cells) and N fixation)few heterocytes) but one cell cannot perform both
Biofilms
Table 27-1
Fig. 27-14
Photosyntheticcells
Heterocyte
20 µm
Prokaryotic phylogeny• Horizontal gene
transfer (ring instead of a tree)
• Archaea more closely related to eukaryotes than bacteria
• polyphyletic
Eukarya
Archaea
Bacteria
Archaea
Eukarya
Bacteria
Fig. 27-16
UNIVERSALANCESTOR
Eukaryotes
Korarcheotes
Euryarchaeotes
Crenarchaeotes
Nanoarchaeotes
Proteobacteria
Chlamydias
Spirochetes
Cyanobacteria
Gram-positivebacteria
Do
main
Eu
karyaD
om
ain A
rchaea
Do
main
Bacteria
Table 27-2
Proteobacteria• These gram-negative bacteria include
photoautotrophs, chemoautotrophs, and heterotrophs
• Some are anaerobic, and others aerobic
Fig. 27-18a
Alpha
Beta
Gamma
Delta
Epsilon
Proteobacteria
Subgroup: Beta Proteobacteria
Nitrosomonas (colorized TEM)
1 µ
m
Subgroup: Delta Proteobacteria
10 µ
m
Fruiting bodies ofChondromyces crocatus, amyxobacterium (SEM)
Bdellovibrio bacteriophorusattacking a larger bacterium(colorized TEM)
5 µ
m
Helicobacter pylori (colorized TEM)
2 µ
m0.
5 µ
m
Subgroup: Epsilon Proteobacteria
B. bacteriophorus
Thiomargarita namibiensiscontaining sulfur wastes (LM)
Subgroup: Gamma Proteobacteria
Subgroup: Alpha Proteobacteria
Rhizobium (arrows) inside aroot cell of a legume (TEM)
2.5
µm
Subgroup: Alpha Proteobacteria• 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
Fig. 27-18c
Rhizobium (arrows) inside a rootcell of a legume (TEM)
2.5
µm
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• 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 even if the prokaryotes that produce them are not present
• Endotoxins are released only when bacteria die and their cell walls break down
• Many pathogenic bacteria are potential weapons of bioterrorism