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The Prokaryotes
Simplest organisms
All unicellular
Lack nuclei
Lack organelles
Peptidoglycan (cell wall)
Multiply by binary fission
Divers metabolism (eat about anything)
Diverse habitats
Bacteria vs. Archaea
- Two different forms of prokaryotes
- Two separate domains
- Very different
- Ancient split
Prokaryote Shapes
 Bacilli
 Cocci
 Spiral
Pleomorphic bacteria can assume several shapes.
Range in size from 2-8 um long and 0.2-2 um in diameter.
(1 um = 1/1,000,000 m)
Some are pathogenic (disease causing), but most are harmless.
Exotoxins and Endotoxins
Prokaryotic Nutrition:
How organisms obtain carbon and energy:
Oxygen Requirements:
Obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes
Many prokaryotes thrive in hostile environments (Archaea).
acidophiles, thermophiles, basophiles, halophiles
Modifications for Survival
1) prokaryotic flagellum
2) pili
3) endospores
4) actinomycetes (fungus like)
Special Prokaryotes
- photosynthetic bacteria
- blue-green
- blooms
Nitrifying Bacteria
- convert ammonia and nitrite into nitrate
- agriculture
Nitrogen Fixing Bacteria
- fix nitrogen gas into ammonia
- root nodules of legumes
Sulfur Reducing Bacteria
- deep sea vents
- may represent earliest forms of life
The Prokaryotic Cell
I. Structures external to cell wall
A. Glycocalyx
- Gelatinous glycoprotein covering
- Includes capsules and slime layers
- Functions:
1. Protect from phagocytosis
2. Adherence
3. Prevent desiccation
4. Feeding
B. Flagella
- Solid, unsheathed, protein
- Filament, hook, basal body
C. Axial Filaments
D. Fimbriae and Pili
II. The Cell Wall
 Rigid structure surrounds plasma membrane
 Consists of peptidoglycan
 Two different types based on structure
1) Gram +
2) Gram –
 Porins
III. Structures internal to cell wall
A. The plasma membrane
- Phospholipid Bilayer with interspersed proteins
- Encloses the cytoplasm
- Mesosomes = irregular infoldings of the membrane
B. Cytoplasm
- Fluid component of cell
- Mostly water with soluble material
C. The nuclear area (nucleoid region)
- Region contains bacterial chromosome
- Plasmids
D. Ribosomes
- 70S (as opposed to 80S in eukaryotes)
- Sites of protein synthesis
- Damaged by some antibiotics
E. Inclusions