Lecture 23

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Transcript Lecture 23

I. Prokaryote Domains: Archaea and Bacteria
A. Evidence of early divergence
1. Archaea: are the “ancient” bacteria
2. Bacteria (Eubacteria): are the “modern” bacteria
3. Domain Eukarya: appears to have diverged from Archaea
(after Bacteria)
- also possible that first eukaryote was fusion of Archaea and
Bacteria
B. Differences between Archaea and Bacteria
Archaea have as much in common with Eukaryotes as with Bacteria
II. Characteristics of Prokaryotes
A. Shape
1. cocci
a. streptococcus
b. staphylococcus
2. bacilli
3. spiral
a. vibrios (comma-shaped)
b. spirilla (helical and short)
c. spirochetes (longer and flexible)
B. Structure
1. cell wall
a. maintains cell shape and provides protection
b. but may not prevent water loss
c. may be encased in lipopolysaccharide membrane
- the lipids may cause toxicity
B. Structure
1. cell wall
a. maintains cell shape and provides protection
b. but may not prevent water loss
c. may be encased in lipopolysaccharide membrane
- the lipids may cause toxicity
d. gram (-): has the membrane
e. gram (+): lacks the membrane
2. pili
a. surface adhesion
b. adhesion to other bacteria
c. sex pili
- conjugation
3. circular DNA (single chromosome)
- maybe plasmids also
4. flagella
- simpler than eukaryotic ones
C. Reproduction
1. binary fission
C. Reproduction
1. binary fission
2. conjugation
a. plasmid transfer
b. replicated and passed through sex pilus
c. used to pass on useful traits
3. endospores
- anthrax, botulism
D. Differences from eukaryotes
1. no true internal compartmentalization (organelles)
2. small size
3. usually just unicellular
- sometimes cooperate metabolically
D. Differences from eukaryotes
1. no true internal compartmentalization (organelles)
2. small size
3. usually just unicellular
- sometimes cooperate metabolically
- biofilms (surface-coating colonies)
D. Differences from eukaryotes
1. no true internal compartmentalization (organelles)
2. small size
3. usually just unicellular
- sometimes cooperate metabolically
- biofilms (surface-coating colonies)
4. no rod-shaped chromosomes
D. Differences from eukaryotes (cont’d)
5. binary fission vs. mitosis
6. simpler flagella
7. metabolic diversity
a. autotrophs
- photoautotrophs (get C from air)
- chemoautotrophs (also get C from air)
b. heterotrophs
- photoheterotrophs (get C from organic compounds)
- chemoheterotrophs (similar to animals)
III. Types of Prokaryotes
A. Archaea
1. extreme halophiles
- extreme salinity (5x’s that of seawater)
2. extreme thermophiles
- even at or above boiling
- thermoacidophiles
3. methanogens
- anaerobic
- swamp gas (bubbles up from mud)
- cow gas
4. many also live in less harsh environments
- ocean (especially deep)
B. Bacteria
1. proteobacteria
a. large group containing gram(-) bacteria
b. N2-fixers
c. animal gut bacteria
2. chlamydias
- urethritis (STD)
- blindness
3. spirochetes
- syphilis
3. spirochetes
- syphilis
- Lyme disease
4. gram-positives
a. staph and strep (typically)
b. many soil decomposers
c. mycoplasmas
- 2 million pneumonias/year US
5. cyanobacteria
a. oxygen-producing photosynthesis
b. major food source for aquatic/marine ecosystems
c. probably responsible for the initial production of O2 on earth
F. Diseases (Section 16.8)
1. attack with white blood cells
F. Diseases
1. attack with white blood cells
2. antibiotics
- resistant strains (13.15)
IV. Viruses
- not alive